LOS ALAMOS NATIONAL i LABORATORY I - JD | 8 00054 9948 3 933 National_ | Academy of Sciences National Research Council NUCLEAR SCIENCE SERIES The Radiochemistry of Uranium U - Atomic N 1. A Commission COMMITTEE ON NUCLEAR SCIENCE D. A. Bromley, Chairman Yals University Martin J. Barger National Bursau of Standards Victor P. Bond Brookhasven National Laboratory Gregory R. Choppin Florida Stats Univenity W. A. Fowler California Institute of Technology Q. C. Phillips Rics University Geaorge A. Kolstad U. 8. Atomic Energy Commission John McElhinney Naval Ressarch Laboratory Robley D. Evamme, Vice Chairman Massschusetts |nstitute of Technology C. K. Resd, Exscutive Secratary National Acsdemy of Sciences Herman Feshbech Msssachusetts Institute of Technology F. 8. Goulding Lawrence Radistion Laborstory Bemd Kshn ; Ngticnal Canter for Radiological Health Members-at-Large Lisison Members Qeorge Wetherill University of Callfornia Alexander Zucksr Oak Ridgs Nstional Laborstory Walter 8. Rodney National Sciancs Foundation Lowls Slack Amarican Instituts of Physics Subcommittes on Radlochemistry Gregory R. Choppin, Chairman Floride Stats University Herbert M. Clark Renmssiser Polytechnic Institute Raymond Devls, Jr. Brookhaven National Laboratory Bruce Dropesky Los Alamos Scientific Laborstory Rolfe Herber Rutgers University John A. Miskel Lawvrencs Radintion Laboratory Jullan M. Nisisen Pacitioc Northwest Laboratory Q. D. O'Kelley Osk Ridge National Laboratory Andrew F. Stshney Argonne National Laboratory John W. Winchester University of Michigan Membership as of January 1972 I I AEC Category NAS-NS-3050 uc-4 The Radiochemisiry of Uranium JAMES E. GINDLER Argomne Nalional Laboralory Argonne, Illinois Iséua.nce Date: March 1962 LOS ALAMOS SCIENTIFIC LABORATORY MOV 7 1978 LIBRARIES PROPERTY Subcommittee on Radiochemistry National Academy of Sciences —National Research Council Price $3.00, which is the minimum order price for either one, two, or three randomly selected publications in the NAS-NS sries. Additional individual copies will be sold in ingcrements of three for $3.00. Available from: National Technical Information Service U. S. Department of Commerce ] Springfield, Virginia 22151 Printed In the United Statss of America USAEC Technical Informstion Centsr, Osk Ridge, Tennmsmes 1962; latast printing 1972 FOREWORD The Subcommlttee on Radlochemlstry 1s one of a number of subcommlttees working under the Commlttee on Nuclear Science within the Natlonal Academy of Sclences - Natlonal Research Councll. Its members represent government, industrial, and unilverslty laboratorlies In the areas of nuclear chemlstry and analytical chemlstry The Subcommlttee has concerned ltself wlith those areas of nuclear sclence which involve the chemist, such as the collec- tion and distributlion of radiochemlcal procedures, the estab- lishment of speciflcations for radlochemlically pure reagents, avallabllity of cyclotron time for service lrradlationas, the place of radlochemlstry 1n the undergraduate college program, etec. Thlis serles of monographs hag grown out of the need for up-to~date compllatlions of radlochemical informatlon and pro- cedures. The Subcommlttee hap endeavored to present a serles which wlll be of maximum use to0 the worklng sclentlset and which contalne the latest avallable informatlion. Each mono- graph collecte In one volume the pertinent Information required for radlochemical work with an indlividual element or a group of closely related elements,. Anh expert in the radliochemlstry of the particular element has wrltten the monograph, followlng a standard format developed by the Subcommittee. The Atomle Energy Commission has sponsored the printing of the serles. The Subcommittee 18 confldent these publlcations wlll be useful not only to the radiochemlset but also to the research worker in other flelds such as phyelcs, blochemlistry or medliclne who wishes to use radlochemlcal techniques to solve a epeciflc problem. W. Wayne Melnke, Chalrman Subcomnlttee on Redlochemlstry 111 INTRODUCTION This volume which deals wlth the radiochemistry of uranium l1s one of a serles of monographa on radiochemlstry of the elements. There 18 Included a revlew of the nuclear and chemlcal features of partlcular interest to the radilo- chemist, a discusslon of problems of dissclutlion of a sample and countling technlques, and flnally, a cocllection of radio- chemlical procedures for the element as found in the litera- ture. The seriles of monographs willl cover all elements for which radiochemlcal procedures are pertinent. Plans include revision of the monograph perlodlcally as new technlques and procedures warrant. The reader 1s therefore encouraged to call to the attentlion of the author any published or unpub- lished materlial on the radlcchemlstry of uranium whlch mlght be included in a revised versaion of the monograph. iv CONTENTS Y. GOeneral Revliews of the Inorganlc and Analytical Chemlstry of Uranlum II. General Revliews of the Radlochemlistry of Uranium ITI. Table of Isotopes of Uranlum 3 IV. Review of Those Features of Uranlum Chemistry of Chief Interest to the Radlochemist 5 A. Metallic Uranium 5 l. Preparation 5 2. Physlicael properties 6 3. Chemlcal properties 6 T B. Compounds of Uranium C. The Chemistry of Uranium in Solution 14 1. Oxidation states 153 2. Complex ion formatlon 21 3. Non-aqueous solutlons of uranium 30 D. Separation of Uranium 39 1. Precipitation 40 2. 8olvent extraction 60 Ethers, esters, ketones, and alcohols 63 Organophosphorua compounds 122 . Amines and quaternary ammonlum salts 169 Carboxylic aclds 180 Chelatlng agents 182 3. TIon exchange 202 - Anlion exchange 204 Catlon exohange 222 . 4. Chromatography 227 5. Volatillization , 231 6. Eleotrochemlcal methods 232 T. Pyrometallurglcal processes 235 E. Determination of Uranlum 236 1. Counting techniques 236 . 2. Sample preparation 241 3. Activation analysis 248 F. Dissolution of Uranium Samplea 1. Metalllo uranium 2. Alloys of uranium 3. Compounds of uranium 4., Meteorites, minerals, and ores 5. Blologlcal samples 6. Ailr dust samples V. Collection of Detalled Procedures 252 252 254 - 254 255 256 257 The Radiochemistry of Uranium JAMES E. GINDLER Argonne National Laboratory Argonne, Illinois General Revlews of the Inorgenlc and Analytical Chemistry of Uranilum. 1' J. W. Mellor, "Uranium" in "A Comprehensilve Treatlise on Inorgenic and Theoretical Chemistry," Volume XII, Chapter ILXIII, pp. 1-138, Longmans Green and Company, London, 1932. R. J. Meyer and E. Pletsch, "Gmeline Handbuch der Anorgan- ischen Chemile," 8th Editlon, Syétem No. 55, Verlag Chemle, G.m.b.H., Berlin, 1936. N. V. Sidgwick, "Uranium" 1in "The Chemlical Elements and Thelr Compounds," PP- 1069-1086, Clarendon Press, Oxford, 1950. C. J. Rodden and J. C, Warf, "Uranlum" in "Analytical Chemistry of the Manhattan ProJject," National MNuclear Energy Serles, Divlision VIII, Volume 1, Chepter 1, pp. 3- 159, C. J. Rodden, Ed., McGraw-H1ll Book Co., Inec., New York, 1950. ., J. J. Katz and E. Rablnowitz, "The Chemistry of Uranium," Natlional Nuclear Energy Series, Division VIII, Volume 5, McGraw-H111l Book Co., Inc., New York, 1951. G. T. Seaborg, "The Actinide Seriles" in "Comprehensive Inorganic Chemistry," Volume I, Chapter 3, pp. 161-223, 10. 11. 12, 13. 14, 15, 16. 17. M. C. Sneed, J. L. Maynard, and R. C. Brasted, Ed., D. van Nostrand Company, Inc., New York, 1953. H. R. Hoekstra and J. J. Katz, "The Chemistry of Uranlum" in "The Actinide Elements," National Nuclear Energy Serles, Divislon IV, Volume 14A, Chapter 6, pp. 130-188, G. T. Seaborg and J. J. Katz, Ed., McOGraw-H1ll Book Co., Inc., New York, 195%4. " J. J. Katz and G. T. Seaborg, "The Chemlstry of the Actinide Elements, " Chapter V, pp. 94-203, John Wiley and Sons, Inc., New York, 1957. "Urenium, " R. Calllat and J. Elston, Directors, in "Nouvesau Tralte de Chemtle Minerale," Part I, Volume XV, P. Pascal, Director, Masson et Cle, Parls, 1960. Part II, 1961. G. Meister, "Uranium" 1n "Rare Metals Handbook," Chapter 26, pp. 501-571, C. A. Hampel, Ed., Reinhold Publishing Corp., New York, 1954. L. Gralnger, "Uranlum and Thorilum," George Newnes Limited, London, 1958, A. N, Holden, "Physical Metallurgy of Uranium," Addison- Wealey Publishing Company, Inc., Readlng, Mass., 1958. "Uranium Ore Processing," J. W. Clegg and D. D. Foley, Ed., Addison-Wesley Publishing Company, Inc., Reading, Mass., 1958. "Uranium" in "Scott's Standard Methods of Chemlcal Analy- gis," Volume I, pp. 1017-1027, N. H. Furman, Ed., D. van Nostrand Co., Inc., New York, 1939. TID-5223, Production end Separation of U233, Collected Papera, Part 1 and Part 2, L. I. Katzin, Ed., 1952. TID-5290, Chemistry of Uranium, Collected Papersa, Book 1 and Book 2, J. J. Katz and E. Rablnowltz, Ed., 1958. G. H. Morrison and H. Freiser, "Solvent Extrection in Analytical Chemistry," John Wiley and Sons, Inc., New York, 1957. IT. General Revliews of the Radlochemlstry of Uranium. 1. E. K, Hyde, "Radlochemical Separetlion of the Actinilde Elements" in "The Actinlde Elements," Natlonal Nuclear Energy Series, Divielon IV, Volume 1l4A, Chapter 15, pp. 542-595, G. T. Seaborg and J. J. Katz, Ed., McGraw-Hill Book Co., Inc., New York, 1954. E. K. Hyde, Paper P/728 "Radlochemical Separations Methods for the Actinide Elements," Volume 7, pp. 281-303, Pro- ceedings of the International Conference in Geneva, August, 1955, on the Peaceful Uses of Atomlc Energy, United Nations, New York, 1956, IIT. Teble of Isotopes of Uranium® , Isotope U227 U228 229 230 231 232 Half-Life 1.3 min 9.3 min 58 min 20.8 day L.3 day 74 year Type and Ener of Radlation %fiev) o 6.8 a (~80%) 6.67 EC(~20%) EC(~80%) a (~20%) 6.42 o 5.884 (67.2%) 5.813 (32.1%) 5.658 { 0.7%) EC (99+%) «(5.5x1073%) 5.45 a 5.318 (68%) 5.261 (32%) 5.134 (0.32%) Method of Preparation Th?32(a,9n) T™h23%(a,8n); ~2% daughter 36 min Pu232 Th®3%(a,7n); ~0.1% daughter 20 min Pu233 Th®32(a,6n); ~15% daughter 17.7 day Pa23o; ~6% daughter 9.0 hour Pu234 ™h?32(a,5n); pa®3!(a,2n); 3 x 1073% daughter 26 min Pu°3° ™he32(q, in) ; daughter 1.31 day 232 Pa ;s daughter 2.85 year Pu236: U233(n,2n) Table of -Isotopes of Uranium (Continued) Type and Ene of Radiationr?fiev) Isotope Half-Life ye33 1.626 x 10° : _year® U234(UII) 2.48 x 10° year g235m 26.5 min U235(acU) 7.1 x 10% year 236 2.39 x 107 year ye37 6.75 day a 4.816 4.773 h.717 k.655 4.582 a 4.768 4,717 IT a 4.559 4.520 4.370 4. 354 %.333 4,318 4,117 a 4.499 g~ 0.248 (83.5%) (14.9%) ( 1.6%) (0.07%) (0.04%) (T2%) (28%) (6.7%) (2.7%) (25%) (35%) (14%) ( B8%) (5.8%) Method of Preparation daughter 27.0 day Pa233 natural radloactivlity 0.0056%; daughter 1.175 mln Pa?3¥M(vx,,) ; daughter 6.66 hour pa23%(uz); daughter 86.4 year Pu238; y233 (n,9) daughter 24,360 year Pu239 natural radioactivity 0.720%; daughter 26.5 min U235m; daughter 410 day Np=3°; daughter 23.7 min Ppo32 51% dsughter Np236~£; daughter 6,580 year Pu2*0; 1235 (n, ) daughter 11 min pa237 g, fifi%fllf% daughter U238 (n, 2n) ; v236(n, ) Table of Isotopes of Uranium (Contilnued) Isotope Half-Life Type and Energy Method of of Radilation (Mev) Preparation U238(UI) 4. 51 x 109 year a 4.195 natural radio- actlvity | 99, 276% U239 23.54% min BT 1.21 U238(n:7)5 : 2 u?38(q,p) 240 . - 107 yesar Puauu; 2nd order neutron capture on U238 2 Data concerning half-lives, radlations and branching ratlos, unleas othefwise noted has been obtalned from the "Table of Isotopes" by D. Strominger, J. M. Hollander and G. T. Seaborg, Revlews of Modern Physics, 30, No. 2, Part II, Aprlil, 1958. This compilla- tion may be consulted for more complete information on the isotopes and for references to the orlginal llterature. o Ya. P. Dokuchayev and I. S. Oslpov, Atomnaya Energiya, 6, 73 (1959). |o J. E. Gindler and R. K. Sjoblom, J. Inorg. Nuclear Chem., 12, 8 (1959). The half-11fe of Pa237 has been reported recently to be 39 = 3 j min, K. Takahashl and H, Morinaga, Nuclear Physilce, 15, 66k (1960). IV. Revlew of Those Features of Uranium Chemistry of Chief Interest to the Radlochemlst. A, Metallle Uranium 1. Preparation. Uranium metal may be prepared by several methods:l the reduction of uranlum oxldes with carbon 1in an arc-melting furnace; reductlon of uranlum oxldes with magneslum, aluminum, calclum or calclum hydride; the reductlon of uranlum halldes wilith alkali or alkaline-earth metals; electrolytic reduction of uranium halides; and the thermal decomposifion of uranium. iocdide. 2., Physical properties. Metallle uranlum exlsts 1n three allo- tropic for-rnes:-g-’-:i the orthorhomblc alpha form, stable below 6£63°C; the tetragonal beta form which exists between 663°C and 770°C; and the body-centered cuble form which exlists at higher temperatures (> 770°C). The physlical properties of the metal as complled by Graingeri'are given 1n Table X. Because of the method of preparation, impurlties may be contalned 1n the metal which alter 1te propertiles. Also, a number of the physl- cal characterlstics depend upon anisotropic and structural effects, eg. thermal expansion. Therefore, 1f physical proper- tles are pertinent to an experiment or design, 1t is besat to determine them 1ndividuslly for the metal used. The changes wrought 1n metallic uranium by radletion and thermal cyclling may be considerable. The results of reactor radla- tion on the metal are: dimensional 1nstabllity, surface roughening and plmpling, warplng, high hardness, extreme brittleness, cracks and poroslty, broadened x-rey diffraction llnes, and decreased thermal and electwlcal conductivity.é- Thermal cycling growth 1s elmllar in many respects to that caused by radlation damage. However, dlfferences exlst, the fundamental difference belng in the mechanism of growth. (The reader 1s directed to reference 3 for more detalled discusalon of this subject.) 3. Chemlcal propertles. Uranlum 18 8 highly reactive metal. A potential of +1.80 volts for the half-cell reaction, U - U3 + 3e, places 1t below beryllium and above hafnium and aluminum in the electromotive force series.-2 The metal forms 1ntermetallic compounds with Al, Be, B1, Co, Cu, Ga, Au, Fe, Pb, Mn, Hg, Ni, Sn, Ge, In, Ir, Pd, Pt, T1, and Zn;= solid solutlons with Mo, Ti, Zr, and Nb.2 It reacts at varying temperatures with H,, B, C, Si, N C1 Br P, As, O,., S, Se, F 27 2’ 2! 2’ Neoq, CHH’ Co, COE' 1,2 In alr, at room temperature, massive o2 I2, HQO’ HF(g): HE'_S’ NH3: NOJ HCl(g) uranium tarnlshes to form a yellow and. eventually a black oxide coating. TFinely divided powder may burn spontaneocusly. In boilling water, massive uranlum corrodes slowly wlth the formation of uran- lum dioxilde and hydrogen. The reaction products with steam are uranium oxide and hydride. The diseolutlion of uranium metal 1s discussed 1n sectlon IV-F. Table I. Physlcal Properties of Uranium Metall Density (high purity) 19.05 + 0.02 gm/cm3 Density (industrial uranium) 18.85 * 0.20 gm/cm> Melting point 1.132 £ 1°C. Bolling point 3,818°C. Heat of fusion 4.7 kecal/mole Vapor pressure (1,600°C.) 10'1‘L mm Thermal conductivity (70°C.) 0.071 cal/cm-sec-°C. Electrical reslstivity (25°C.) 35 x 10° ohm/'cm3 Mean coefflcient of linear 16 x 10’6/”01 thermal expanaion (random orientation 25-100°C.) Specific heat (25°C.) 6.65 Enthalpy (25°C.) 1,520 cal/mole Entropy (25°C.) 12,0 cal/mole/°C, 2 1. Gralnger, reference &. Iv-B. Compoundes of Uranium Uranium comblnea with most elements to form a large number and varlety of compounds. "Gmelins Handbuch der Anorganischen Chemie,”é which surveys the llterature through the year 1935, deacrlbes seversl hundred compounds. Ketz and Seaborgg describe some of the more recently prepared compounds, princlpally of organlc character, such as chelates, alkoxldes, amldes, mercap- fides, and w-cyclopentadlenyl compounds. The oxldatlion states of uranium in the comblned form vary from IT to VI. Divalent uranium compounds reported are U0 and US. Trivalent uranium compounds are more numerous and include the hydride, nitride, seaqulsulfide, halides and borohydride. Uranium (III) sulfate UH(SOu)2 has also been reported.-I A large number of tetravalent compounds are known varylng in complexlty from the oxide and simple blnary salts to more com- plicated organic structures. Complex salts such as 3(CN3H6)2003- U(CO3) 4H20 and E(NH4)2C204 . U(caou)2 * 6H,0 form an impor- 2 tant group of uranium (IV) compounds. Complex salts are formed also with halide, sBulfite, sulfate, and phoephate lona. Inorgeanic compounds of pentavalent uranium are UF5, UCl5, fi015 . 80012, 8 UCl5 . PCls,é and UF5 ' xHF.é UOCl3 has been reported as an lnter- nmedlate compound 1in the chlorination of uranium oxlides with carbon tetrachloride.l Uranium (V) alkoxldes have been pre- and UOCl, - EtOH 5 3 have been reported.g- Hexavalent uranlum 1p represented by pared.g Also, the compounds (C5H6N)2 Uocl UF6, UCl6, U03, uranates, and uranyl (UoS*) compounds, Uranyl compofinds are the moet numerous uranlum compounds and vary in type from simple salts to complex organic arrangemente. Complex salts are formed with hallde, lodate, nitrate, carbonate, cyanide, acetate, oxalate, sulfate, phosphate, arsenate, chromate and vanadate lons. Tripie acetate salts of the form I MM (00,) 5(CH4CO,) g + 6H,O, where ML 13 an alkall metal (L1, Na, or K) and ML 18 a divalent metal (Mg, N1, Zn, ete.), are used in analytical separatlions of uranium. Addltion compounds, such as U02(NO 2CH,COCyH 3)2 3 repregent a large number of uranyl compounds. 9.' Uranatesa and peruranates are lmporftant in the analytical chemlistry of uranium. Uranates have the general formula xMIO . 2 yUo., or xMIIO . yU03. They may be prepared by different me‘chods.—s-’--l-9 3 However, in usual analytlcal procedures, they are preclpitated from a uranyl solution by the addltlion of a soluable metal hydrox- ide, NH40H, NaOH, Ca(OH)E, etc., The uranates are insoluble in water but dlssolve 1n acids. Per'ura.natea§ are formed when uranyl sclutlions contalnling hydrogen peroxlde are made alkallne. The composltion of the peruranates depends upon the concentratlon of the slkall and peroxide. The following groups have been ldentifled: M2U2010 . xHEO, M2U06 . xHEO, M6U2013 . xHEO, and M4UOB . xHEO. The peruranates are generally socluble in water. The least soluble are those of the M2U2010 . xH20 group. The peruranates are soluble 1n dilute mineral aclds. Table II liste a number of uranium compounds togéther with thelir behavior in different solvents. The compounds listed are primarily bilnary compounds or slmple salts. The order in which they appear 1s the order in which they may be found in "Gmelins Handbuch der Anorganischen Chemile." 6 Table II. Uranlum Compounds and Thelr Sclvents. Compound Solvent UH3 . 8. HNO3(vigorous), cone. HC1Oy, hot conao. HESOH’ a. +H,0, 1. alk., 1liq. NH 2°2 3 U02 B. HNO3, aq. reg., conec. Hasou, slowly converted to U({IV)-salts in hot fum. HC1 U308 8. HNOB; heated to redness U308 1a only v. 8l. s. dil. HCl and H,S0,, more 8. conc. - 2., 8. hot conec. Hesou; HF forms s. U02F2 and 1, UF4 UO3 8. mineral a. UO2'xH2Q[U(OH)4'(x-2)H20] 8. dill. a. U3OB . xH2O 8. 4. UO3 . 2H20 8. 4., converted to UO3-H20 i1n bolling HEO Table II. - Continued Compound Solvent U03-H20,[H2U04,002(0H)21 8. a., warm conc. UOe(NO3)2 aoln. UO"_ - 2H20 U3N4 U0, (NOg), - 6HyO a UFy, UF5, U2F9' U4F17 UFg U02F2 UCl UClu UCl UClG UoC1 Uo,Cl UBr3 solubility in H,0: 20° C-.0006 g/100 ml, 90°¢-.008 g/100 ml; d. HCl; alk. hydroxides form UO3 and B. peruranates a. HN03; i. cone, HCl, Hasou solubility in H,0: 0°C-170.3 g/100 ml, 60°C=goluble in all proportions; a. al., ether, acptone, daill. a. s. h. HC10y, h. HNOg, h. Hy30,, H,B0, + mineral a. i. H20; 8. fum. HGlOu, HNO3 + H3BOB; metatheslzed to U(IV)-hydroxide by heating with NaOH d. Hao forms s. anF2 and 1. UFu B. H20-visoroun reaoction, cclu, GHCls; v, 8. CEHECIu; d. alcohol, ether B. H20, alcohol; 1. ether, amyl alcohol s. Hao, HC1l, glec. acetlic a.; 1. 0014, GH013, ecetone, pyridine 8. HEO, CEHBOH’ acetone, ethyl acetate, ethyl beneoate; 1. ether, CHCl benzene 3! .. Hzo(d.); abmsolute alcohol, ethyl benzoate, trichloracetliec acid, ethyl acetate, benzonitrite, 052, S0C1 2 d. H20; 8. 0014, CHCl3 8. H20 8. H20: 18°C=320 g/100 ml; 8. alcohol, ether a. H20 8 41- and tri-hydrates are also well established. 10 Table II. - Continued Compound uo » H,0 2( 3)2 2 us U2S3 Us Uo,S U02803 . 4H20 U(SOu)e * 9H,O U(sou)2 * 8H,0 U(sou)z ’ 4H20 U0304 . EHEO UOESO4 . 3H20 U02504 . HEO USe2 UOESe Solvent B. HEO, acetone, methyl- and ethyl-acetate, pyrldine; 1. ether B. HEO 8. HEO‘ alcohol, ether 8. H20 8. H20 v. 8l. 8. H.0: 18°C-a form, 0.1049 2 g/100 ml, B form, 0.1214 g/100 ml; cold ppt. B. HNO3 and H3P04, 1. a. after previously heating to boliling temp.; 8. alk. carbonates v. difficultly B. cone., HCl, dil. HNO3 +0 aq. reg., conc. HNO3 d. steam, HNO3; B. hot conc. HCL gl. s. H,0; 8. dil. a., alcohol, (NH4)2003; 1. abBolute alcohol 1. H20; B. 8q. or alcohollic SO2 solution hydrolyzee 1n H,0 wlth separation of 2 basglc sulfate, UOSOu . 2H20; 8. dil. mineral a., acetlc a. hydrolyzes in H,0(d.); B. dil. H,S50,, HC1 8. a. _ s. Hy0: 15.5°C-20.5 g/100'ml, 100°C- 22.2 g/100 ml; s. mineral a. 8, H20 lgnites wlth HNO3; chemical propertles gimilar to U82 4. H20; g. cold HC1l - forma U02012 11 Table II. - Contlnued Compound UC,5e0, * 2H,C UB 12 U(BHu)u UcC U02003 er(Hcoe)2 " H,0 U02(H002)2 » U0 3H,,0 G U02(0H3002)2 " 2H,0 U(0204)2 . 6H20 U020204 : 3H20 U(04H406)2 - 2H,0 U02(04H406) . 4H20 er(CNs)2 * 8H,0 Solvent and HESe; reacts violently wlth HNO3 - Se 18 first -formed and 1s then oxldlzed 1. H.O0; s, HC1 2 8. aq. reg., HNO HF 3! 8. cold HF, cold HC1, HN03, cone. H2 Y reduces conec. Hesou 1. hot cone. HCl, HF; slowly B. hot conc. HESOH d. H20, alcohol d. H,0, dil. HC1l, d411. HNO dil. H2804; 2 3’ reacts vigorously wlth heated conc. a. 8. a. 8. H20: alcohol; 8l1. a. formle a.; 1. ethyl 15°C-420 g/100 ml; a. methyl glcohol, ether, acetone, CS 0014, o2 CH013, benzene, petroleum ether less 3. HEO than neutral salt; more 8. formlc a. than neutral salt s. Hy0: 15°C-7.69% g/100 mi; v. 8. alcohol; 1. ether 1. HEO’ dil., a.; 8. warm conc. HC1, conc. HNO3 sl. 8. H,0: 14°C-0.8 g/100 ml, 100°C- 3.3 g/100 ml; s. mineral a., H,C,0, and alk. oxalate solutlons 1. H20, organic solventsa; s. tartaric a., tartrates, conc. =a. sl. 8. H,0: 17°C-3.28 g&/100 cc solutiomn 8. H,0, ethyl and amyl alcohol, acefione, ether 12 Table II. - Sontinued Compound USi2 U(H2P02)4 - xH,.0 2 U0, (HyP05) 5 U(HP03)2 ’ 4H20 UO,HPO, US(P04)lL UH2(P04)2 * 2H,0 (U02)3(P04)2 » XH,0 UOHPOy - xH,0 UPEOT (U0,)Pp0, + 5H 0 U(Pos)4 UOE(POB) U3Asu UB(Asou)llL UHE(A504)2 * 3H,0 2 UHE(A304)2 - 2H,0 UO HABO) - HHy0 (U02)2 A0, 5U0, * 38b,05 * 15H0 . v295 + XH,0 UO3 U0y ¢ Vp05 * HLO 200, « V,05 TVOLCrO, + XH0 Solvent 1. cold or hot conc.: EHCI1, HNO3, Hesou, ag. reg.; 8. conc. HF; converted to gilicate and uranate by molten alk. and alk. carbonatea at red heat d. bolling conc. HN03, aq. reg., alk. hydroxide 1. H20, dil. a.; 8. conc. a., 50% H3PO2 1. H20, ail. H25045 8. HNO3 1. H,0, 411. a.; 8. conc. &., 50% H3PO3 1. HEO’ dil. a.; B. conc. a. i. H20; attacked by a., €8D. HNO3 8. conc. HC1 1. HEO, acetlec a.; 8. mlneral &a. 1. H,0; 8. mineral a., xs.(NHu)ECO3 1. H.0, cold a. 1. H.0, alcohol, ether; =. XB. N34P207, 1. H, 0, HCI, HN03, H2504 1. H.0; 8. dil. a., esp. arsenlc a. 1. H,.0, acetle a. 8. aq. reg., hot cone. HELl, d. HNO3 13 Table II. - Contlnued Compound Solvent U(M004)2 8. HC1 U02M004 1. H20, CHCl3, benzene, toluene, ether, alcohol, acetlc a.; 8. HC1, H,S0y, HNQ3, H28207 3UO3 . ','r'MoO3 1. H20; 8. minersal ga. . ' . HN UO3 8Moo3 13H20 8 03 UO2 . 3WO3 . 6H20 8. HCl; 4. HN03; 1. H2804 UO3 * 3W‘03 . 5H20 8. H20 UO3 ’ WO3 . 2H20 sl. 8. H20 Abbreviations uesed: a. - acld fum. - fumling alk. - alkalil h. - hot aq. - agqueous 1. - Insoluble ag. reg. - aqua reglas 1. - liquid cone. concentrated 8. - soluble d. decomposes sl. - 8lightly dil. dilute V. - very esap. eapeclelly X8. - excess Iv-C. The Chemletry of Uranlum 1n Solution 1. Oxidatlon states. Four oxldation states are known for uranium ilons 1n aqueous solution: the trl-, tetra-, penta-, and hexapositive states. sented as U+3, U+4, UO2 + 11+ and UO2 Ions 1n these states are usually repre- 2 s respectlvely. The potentlals between the various oxidatlion states are glven velow for aeldlc and basle solutions.2 Acldic solution: yL:80 +3 0.61 1 M HC10, at 25°C T -0.33%4 l 14 Baslc solutilon: . y2e17 U(OH)3§LL& U(oH)ugiég U02(0H)2 Triposltive uranium, U+3. Evlidence for the existence of U*3 comes from the reversibllity of the U(III)/U(IV) couple. Solutlons mey be prepared by the dissolution of a uranium trihalide or by the electrolytic reduction of a uranium (IV) or (VI) solution. Chloride, bromide, 1lodide, perchlorsate arid sulfate solutions of uranium(III) have been reported.ll They are deep red 1fi color and unstable, wlth oxidatlion of U+3 to U+4 occurring and hydrogen being evolved. Strongly acidi- fled Bolutionulg or those kept at low temperaturealg appear to be more stable. Tetraposltive uranium, U+4. The exlistence of the T +i ion 1n solution has been confirmed by measurement of the acid lliberated on dlssolving UClu i3 and by solvent extraction studies of U(IV) with thenoyltrifluoroacetoneli& and acetylacetone.IEB Uranous sclutions may be prepared by dle- solution of a water-soluble salt: the chloride, bramide, lodide, or sulfate; by dlssolutlionh of uranium or a uranium compound 1n an approprlate solvent, e.g., uranium metel in gulfuric or phosphorlic acid; or by reduction of a uranyl solution by chemical, electroochemical or photochemical means. The Bolutions are green in color. They are stable 1n the qbsenca of alr but are oxidlzed by oxygen. Uranlum(IV) under- goes hydrolysis with evidence 1n the flrst stages for the formation of the mononuclear specles, U0H+3. 13,15-18 Poly- merlc specles also are formed which apparently are not 1n equilibrium with the monamer.23:12:19 mietanenil found that in addition to the monomerlc specles, e polymer of the type U[(OH)lefi"'n could account for the hydrolyseils of urenium(IV) to good approximation. Table IIT, based primarlly upon the date complled by Bjerrum, Schwarzenbach, and S111én,22 15 Ion Method nagnet ap ap Bp 8p sol 8p U02 gh gl aol 24+ uoz" qh gl qh, gl gl, fp, Bp gl, fp, BP p(H,0) 80l - 8p dist gl gl 2+ UO2 gh, 81 gh, 8l 25 10-43 10-43 15-25 25 25 25 25 25-26 20-25 25 B & 8 3 257 25% 25 25 25 25 25 25-49 25 25 25 Table II1. Hydrolysis of U Medlum ar €(NaC10y) 0.5(NaC10,) -0 0.19(HC10, ) " 0 oorr 3(Na)01ou 0 oorr 2(0104') 0 corr var vaT 0 corr c[Ba(NoB)EJ 1(Na)c10, 1(Na)c10, 1(Na)c1o4 0.15(KNaC10,) ©.1 Cl0y 2U02(010#) +U03 0 aorr var 0.1(Na)C10, 0 corr 0.3#7[Ba(c1ou)2] 0.0347[Ba(c1ou)2] 0.0347[31(010;)2] 1(Na)C10,, 2+ 0.4U03 3(Na)Cl0,, 1.4003* M and UoS* roms? ‘-Iog of equilibrium constant, remarka ¥ -2.30 -1.63(C=2), -1,56(C=1), -1:50({C=0,5) -1.90{10°), -1.47(25°), ~1.00(%3°) -1.12(10°), -0.68(25°), ~0.18(k3°) = 11.7, a%8; = 36(25°) -1.38(15.2°}, -1.12{2%.7°) " R * » o o - A'E; = 10.7, A'Sl = 33, 43, = 52 *xl -2,0, tflgfi,n+1 «l.2-==3.4n Ksg -3.770"u(on), (5)"] 7 -1.68, fK -1.73% R LA H\0 g UOHSY 4 Ht $x, : U+ 00 2 vop®t 4 bt "6, : UM + 250 3 U(0R)2F 4 ow *Ban,pay ¢ ()M + 30,0 = UL (0H) IR 4 3oR* 'K, -h3 "By -5.87 "L, -1.50, *B,, -4.95 ev U0,N040H, U0, (KO,),0H°" *x, k.09 *Boy -5.97(0=0.6), -5.72(C=0.06) 'Kl ~4.70(?, Bee rer. 43}, ev polyn opx '_F* )3 '*52n,n+1 0.30---6.35n *flan_n+1 0.30--=6. 40n "Bop -5:9%, "Byy -14.29 K, [030g(0M)2™) : -3.55(n=0), -6.5(n=1), -7.4%(n=2), -11.0(n=3), -11.4(n=4) *Bap -5.94, '543 ~12.90 v (U0 0K)2*, not vo,08* 6.08, "%, 1.90, X, -3.60, X, -3. 'xso 5 0 33 - 8y 317 'Kl -%.14%, ev polyn opx K, -k.19 K, -4.2, fxa -5.20 'fl22 -5.06, lbza_ -1.26 - ", -5.40, "8,, -5.82 ™, -5.82(25°), -5.10(20°), A"H,=20.8 - *8op -6.15(25°), -5.92(40°), a’n322-5.7 * - A Sl - 1.3, A”8 - -6 * % " Ba 512 -3.606, fi22 ~£.02 'fllz - 3-68' '522 = 6.3, *343 I-lE.G(qh), *Byy - 12.9(a1) *Bon,par T (041)I02Y + 2n0 e U0, [{0R),00,15% + 2nk* ete. a ~ After J. Bjerrum, G. Schwarzenbach, and L. @. Sillfin, raference 20. 18 Refarence 21 13 22 13,21 16 16 17 23 18 49 37 38 25¢ 39,52,53 32 L2, eri3y 42, arsh Lo L4 4B 50 51 45 46 16 46 &7 47 -0 0.1 1 Moo, 1(rat10,) I(mo._) 1{m)c10, Takls IIT (Contined) The notation ussd Iin this amd in the tahles on aoxplex iam formaticn 1 mabtternoed wiber that used by Bjearrum, Bolmmresenbach, fimfi.m-n The sxplzsation of e tabls which follows ia taken primarily from pard IT of referwnds 20 and this shonld bé conmlted for fariher details eonoarning petation, Fart I of reference 20 mxy he oansultsd for a Assoription of tha varicos swthods by whiach equilibrizns oconstarbs ere debarerined. Oolusn ana, "Yem," refars to the canirul ion N about whioh the camplex is formmd. Oaloem two, "Method," refars to e awbthod Wy whish the omoatants were measured. The abbreviations ussd are: al ex anion exthinge ombrifugs or ultrecantrifogs calarinebkry sondustiviby digtibutiss between wo phasen aal, oot spaalfied fresaing paint glass algotrods 1on exchangs t mgmatio sussspbibility p{E0) partisl pressure af substanse indleated o ihERE Oolumn thres, "T," gplves tha tamparaturs in “C, ’555.‘.193.!" Agy0o0y ? A mathod, not speoifisd polarography premrative waork quinhyirors electrods axf with redox slechrode lnlu‘bfllhl" speatrophotomatry I-ray diffraction sombinabion of tharmedynewis.data axf mmsoremant with P4 alsatrods wnf cpaguresmmb with Ag,0.0, eleatrods mathod oot knawn to empllers " 1ndi- oxbes room temperatmre, ind "t" is wsed if the bemparmture is um- nom o the oampllers. Oolomn feur, "Kedizm, " dsnotes the mture of the msdium to wbich thw squilibtcium ooostents refer. T caooantiretlons glven in tarms of mnles par libar or males par idlogram are not dis- tingol s Symbols nasd e omstants axbtrapolated to mare lanlo strangth. constants ocrrected Eo wero lopnis stremgth by application of scme thaoretiocal ar s=pirieal Tormala. an ianie stremgih af 0.1 mols par litar. consba=t emomntrution of the subrhancs stated (1 mole per liter NaClQ,). laonio stremgth hald canstant abt walus ptated (1 mole par litar) by sddition of the inert salt Indieated. peasurensnts made at & sariss of lonie strengths (I) with BaCl0, as the inert malt. camuentration af the anian (010") hald sanstant at tte valus stated () male par liter) 0(010._") ater is tha salvent unless otharwiss ntated. with the lon shown in parenthases as She inart u.t.‘l_.m. meamresstbs mads ot & sariss of porohlorats oonoentratlions. dilute solution, oconéanbrebion usually not more than 0.01 mole par litaer. lonio msdice varied, and in some cases mo spacial attemph was mmdse b0 oconiral the ionis abrength. tha madizm was minly sqwecusy EC1 ab varicas concantrations. sthanol as solvent. wvarious organis salvemts. 508 mathancl-wntar as solvent. Calumr five, "Log of emilibriom constamt, resmvis.” Tha K, &" mans "log) I, = 6% ‘l2 5 3" maans fln;lol! > 3% 1.9., the "log® and "=" mymbols are axitted. Capesnbtrations [ 1 are usually expressed as mnles par litsr, bot is not disticgnished from wolss par kilogrem. Presmures p Following oonventicns are used ) ars in smospheres. Tha equilibrive conatarmks refer.to varioos types of reantions indicased ar the naxt page. 17 Table IIT {Qontimued) 1. Conasocutive or mtap-wles conatantmi K a. Addltion of ligend {L) (M, ] Wi+ e Mg B o " by 35 b, Addition of protonated ligend (HL) with slimipation of protan tr, 1 1] (M, 5 1(EL] 6. Addition of protonated ligam? (EPI.) + * ML, +HL 2 ML +E Txo- [n(E I.)n] (N(BL)y o R D W(E_L) plna + Bl = FHL), HLXK- 4. addi‘ion of cantrul stom (M) [HnI-] LiNea N " % D, L10 En- 2. Cumilatlive or gross conatantm: p In B, and B the subscripts n end m denots tha camposition of the complex M I, formed. UWhen ll- 1l, the Bacond mubdoript 1a omitted, a. Additlan of gemtral atams (N) end ligands (L) (L =™ + al. Fb lI:lI'I.'l [H]n[L]n Pop = b. Addition of centmal atoms (M) end protonated ligands (HL) with sliminatioen of Protons DE, 1 (R + - o + nHL = M L + oH Bm = W 3. Solubility constanta: I. a. Solid "aI*b in squlilibrium with frees icnes in solublan MLy (8) e a + b Koy - ot n® b. So0lid M;I, in equilibrium with couplex M I snd ligand L in solution T Maly(8) o Moty + (2 - nlr E, = [u‘LnJ[L]"-iE - 2] "m tha subsoripts n ard @ dencte ths composition of M the camplex Han formad in solutlon. When m = 1, the seoomd mabsoript s omitted. In K, ¢. Protoneted ligand resots with ths elimiratian of proten Do) + (B - nE @ang, + (3R n)m mb o r 11 G 2 o Dl m [H+] (T -l.'l) 4. Aoidio and bhaslec gonstants: n. When L ia hydroxide (0E7), M, 1@ water mmd 'l[n is the nth aoid dlasscelation constant for tha hydrolysis of A mevailic lon. b. The use of H' as tha cantral ston to repressnt pro- tolytle constants is illustrated by 1.d. above. - 0. Other acidic oanstants Are deroted by K., followsd > by parenthessas ancloaing the formula of tha specied domating the protom. d. Basioc oonstants are denoted Wy “b follow, 1f nacessary, by parenthases enclosing the formula of tha spaoiass accepting the proton- 5. BSpesolal oonwtantm:s a. X (equation] ) The eguation definas the reactien to which K refers. v ', tx ™a oorrespanding reaction is given in parentheses arter tha oonrtant when the latter is riret used for a particular ligard or cantrel atom, or the reaction is siven immediataly below the egullibriun constants for & particular ligand or ceptral atom. o. (formula) Tha formula gives the ocomposltiaon of tha cqlple: in terns of the speciss frow which it 1a formed. Specias with nagative subsoripts are eliminated in the rformation of tha omm- plex. 4. K, (foraula) The formula gives thd composition of the solid phass in terms of ths species with which it is in equilibrium in aolution. Speciss with negative subsoripts are sliminated in the formatilon of the solla. Heat ocntent and entropy ohanges sre included in column fMve. AH 1s ususlly written in idloocalories and AS in oalories par dagres. Thay ire related to the corresponding cumulative a:u.uimm conatants as follows: B, AEBn; Brm* AEBm; 'flm. A fl_- Wnere the symbol X is uped for the sfuilibrium constant, Eor 8 lu given tha pane sumPMaaript or subsaript aa ths corre= eponding K: e.g., K, afy) Ky, 8E, 0 "l(m, n*l\lnfls eto. Other abbreviations ussd In column five are: [ Kan evidence for the existemos of the vomplex H“I.:l opk scmplax ont cationic enl anianig unsh uncharged pelyn polymiolear ¥ mathors' doubt sxprepssd in referencs glven (1) compilars' doubt Columnh six, "Hslerences,™list the references as they arm A reference such as "5,af.95" indicates that calouwlations have pesn mads in relerensce 25 based fourd at the and of this work. upon data in referense 6. 18 sumarizea the results of several studies on the hydrolysils of the uranium(IV) ion. Pentapositive uranium, UOS . The existence of uranium(V) ion 1n solution has been.conflrmed by polarographlce measure- 24-26 ments. Support for the U02+ 1ion comes from the reverai- bility of the U(V)/U(VI) coupleZl and from infrared2S and crystallographicggiig studles of uranlum and transuranlc ele- mente, Solutions of U02+ may be prepared by dissolution of U015§£ or by reduction of a uranyl solutlon, electrolytilcally or with U(IV) 1ons, hydrogen, or zinc ar.l:l;.algam.l‘i The formation of U(V) 18 an ihtermediate process 1n the photochemlcal reduction of U(VI) in a sucrose solutlon.=2 The solutlons are unstable and dlsproportionate to U{VI) and U(IV). The rate of dis- proportionation is second order 1n urenium(V) concentration "and first order in acid concentration.ifiili The U02+ lon 18 most stable 1n the pH range of 2 to 4,22 Tt is oxidized to the uranyl lon by molecular oxygen, Fe(III) and Ce(IV).lé +2 Hexapositlve uranlium, UO2 A number of phyeical-cheml- cal measurements as well as cryastallographle, infrared and Raman spectra studles support the exlstence of U{(VI) 1on as Uozafngg Uranyl solutions are easlly prepared by dls- solutlion of water-soluble salts: the niltrate, fluoride, chloride, bromlde, lodlde, sulfate, and acetete. Other water- goluble uranyl ealts Include thoee of other organlc acids: the formate, propionste, butyrate, and valgrate; and certaln double salts such as potasslum uranyl sulfate, sodlum uranyl carbonate, sodlium uranyl chromate, etc. Uranyl solutlons may be prepared also by diasolution of a uranium(VI) compound in an approprilate solvent, by dissolutlon of a lower valence uranium compound 1n an oxldilzling medium, or by oxlidatlion of lower valence uranlium lons already 1n solutlon. TUranyl 8olutions are yellow 1n color. They are the most atable of uranlum aolutlons. As 1ndicated 1n preceding paragraphs, the 19 uranyl lon may be reduced by reducing agent&ii or by electro- chemical or photochemical means. The degree of dissoclatlion of uranyl salts 1n aqueoue solution varies. Uranyl perchlorate ie apparently completely d:l.slsoc:‘l.at‘,ed;-:-L-9 whereas, uranyl fluoride 18 undlssociated and tends to form dimers (see section on complex lon formation - IV-C2).3§L§§ Hydrolysle of the uranyl lon has been the subJect of extensive 1nvestigatlon. Conalderable evldence has been adduced for the formation of polymeric species of the type Uoz(Uo3)§+.3kEZ According to Sutton,flg formation of polymers beyond the trimer U3082+ is negliglble. However, the trimer itself may undergo further hydrolysis with the formation of U308(0H)"', U50g(OH) 5, and eventuelly anlonlc species.flg&il Ah]:-land,-ltg in hils origlnal paper, proposed the formation of the monomer UOE(OH)+ as wall as peolynuclear species. In a reappralsal of the work, Arhland, Hietanen, and S1114n23 stated that there was no cartain indicatlion of mononuclear complexes being formed. Rather, the experlmental data was explalned on the basis that complex lons of the type U02[(OH)2U02]$1+ were formed. From the data 1t was not possible to distingulsh between a limited mechanism in which n variled from 1 to 3 or 4 or an unlimited mechanism in whlch n assumed all integral values. The authors were lnclined to prefer the latter. I‘&'.r-a'us--:l-'-2 suggesated that reactlons leadlng to the formatlion of polymers mey have & less poeltive value of AH than the reactlion leading to the formation of the monomer. Consequently, the latter process mlight be ldentlfied more readlly at high temperatures than at room temperature. Thls is apparently the case as was shown by Hearne and 1.'u'hitc-:-i‘l-g who determilned the enthalpy change to be 20.8 kecal/mole for the monomerilc reaction (UO,OH' formed) and 6.7 kcal/mole for the dimeric + reaction (U20 formed). Table III summarlzes much of the 2 5 20 data avallable on the hydrolysls of the uranyl lon. Included in the table are values of the equllibrium constant K., the 12 constant for the formatlion of the monomerlc species. Thils constant has been evaluated by at least seven groups of :I.n\'reE;’c.’Lgator's--aégféfiiflg?fig:él excluslve of Hearmne and Whiteié. The values obtalned agree very well (log *Kl = -4.09 to -4.70). However, the experimental c:ondj.til.ons-g-és-ng-’-é9 and assump- tionsgé&iig'used in some of the evaluatlons have been 42 questioned.fié Algo, the re-evaluatlon of Ahrland's— work already has been mentlioned, and Rydbergil has proposed an explanation for not detectlng polynuclear gpecles in hils experiments. None-the-less, one must concur wlth R:grdber'gél who wrote, "---1t seems remarkable that the same constants should be obtalned for a filictlve mononuclear hydrolysls product with different U(VI) concentrations and so different methods of investigation---." Complex lon formatlon. The abllity of uranlum to form complex ions 1n solutionse 1s of conslderable importance 1n its analytlcal peparation and determination. Hydrolysis, mentloned 1n the previous section, is but a speclal case of complex ion formatlon. Numerous complexes have been r-eported.z’-i However, the amount of quantitative data for the varlous ligands 1s rather llmited and often contradictory. Tripositlve uranium. Evldence has been reported for uranium(III) cupfer'rate-éi and uranium(IIT) chloroié complexen. Tetrapositive uranium. Inorganic complexes of uranium(IV) wnlch have been recognlzed through the Tormation of ccmplex salts include the fluorlde, chloride, sulfate, sulflte, and phoe;pl'l.'sate.z’-E Table IV llsts the equilibrlum constants and thermodynamlc data avallable for some of the uranium(IV) complexes in aqueous 6= solution. In additlon, a carbonate complex, posslbly U(COB)B s has been found to be stable in solutlone of excems carbonate or blcarbonate ions.éi 21 b+ Table IV. Complex Formation with U Ions - Inorganic _1'.u:I.sn.m‘.|s.E Complexing agant Method T Medium Log of equilibrium constant,remarkas Reference Thiocyenate; red 20 1(NaCl0y), 0.68' K 1.39, K, 0.A6, K; 0.23 57 SCN” atst 10 2(Ra)C1q, 18" K 1.78, K, 0.52 58 " 25 n K 1.49, K, 0.62 58 ARy= -5.7, ABy= -1.8, AS;= -10, A3,= 9.7 " ko " K, 1.30, K, 0.68 58 Phosphate, sol 35 var v UAIS(HL)g+br TAlg (D)3 2* 59 Pog " Sulfate, 505~ atet 25 2(HC105) :‘i 2.53, ::2 ~0.13 12a n " " X 2.4, 'K, 1.32 1%a,cf. 60 " n " K, 3.2%, K, 2.18[K (§)1.125](%) 1%a,0f. 60, 61 n 10 2(Na)Cl0,, 1H* x 2.63, 'K, 1.3 58 - " 'x, 2.52, 'K, 1.35 58 8H)~ -3.2, ARy= 0.9, AS;= 0.7, AS,~ 9.3 " %0 n *x, 2.38, 'K, 1.38 58 Fluoride, F~ ast 25 2(Kac10,), iE* 'K 36, "B, 38 58 Chloride, C1~ Bp 25 0.5(H3010') K, -0.20 13 " 25 0 corr K, 0.85 13 red 20 1Na)clo,, 0.6H7 K, 0.30 57 atst 10 2(NaCloy), 18" K o.52 58 " ' 25 " K 0.26; or K, 0.08, K, -0.02 58 " 40 " K, 016; or K, -0.0%, K, -0.06 58 anl ex 25 HC1 var ev ani opx in >5.5M HC1 62 Bromide, Br~ red 20 1(Na)c1o,, 0.6H* K 0.18 57 a TAfter J. Bjerrum, G. Schwarzenbach, and L. G. $1116n, reference 20. Column one denotes the complexing ligand (L). The notation 1s explained following Table III, Numeroué organic complexes are formed with the uranium(IV) lon: the acetate, oxalate, tartrate, malate, citrate,.lactate, glycolate, etc.ifi However, the amount of quantltative data available on thelr formatlon 18 very meager. Tishkoff-éi has calculated dlssoclation constants for acetate complexes on the basis of the oxygenated uranium(IV) ion UO2+ being formed. The formatlon constanis measured for acetylacetone, thenoyltrlfluoro- acetone and ethylenedlamine tetraacetic acld complexes are glven in Teble V. Pentapositive uranium. Although it appears that uranium(V) complexes should be formed 1n the reduction of uranium(VI) ions 22 in complexing.media,éi little data 1s avallable. Hexaposltive uranium. Inorganic uranlum(VI) complexes which have been identified through the formation of crystalline saltts Include the fluorildes, chlorides, nltrates, sulfates, carbonates, cyanldes, and phoaphates.Qi Uranyl solutlons with these anlone present have been studled. The results are listed in Table VI. A number of dlscrepanciee appear 1n the deta. For example, evlidence for some complexing of the uranyl ion wilth nitratezflizgizz and chlofidcsT’Ts’77’105_107ions hes been reported by some 1investigators; but a complete lack of evidence'has been reported by o‘chers.ég Day and Powerszz have polnted out that the constants calculated by them are concentration constants rather than activity constants. Consequently, the small complexing effect may be caused by. the varlatlon of actlvity coefflclents with a change in medium. Other investigators, however, who have corrected their resulta to apply to pure aqueous solutlona have found some complexing to occur with the chloride ion.éz-"-lgéfl'-gz The type of complex formed between uranyl and fluoride lone also 1ls subjJect to some questlon. Ahrland and co-workerslggiigi have determlined equllibrium constants for the formation of complexes U02F+, Uo,F U0, F, , and UOEFME_ and found no evidence 2 2’ 273 for the dimerlzation of U02F2 for uranyl ion concentrations less than 0.1M. Day and Powers,ZI however, found no evlidence for the formatlion of complexes beyond U02F+; and Johnson, Kraus and Young:’lé have reported the dimerization of U02F2 in solutions not very different from those lnvestigated by Ahrland, gE_gl.lgfl Numerous organlic complexee have been reported.-:'-"-i Much of the quantitative data 1s summarized in Table VII, There 18 often dleagreement between different 1lnvestligators csncerning the nature of the complexing ligand. Uranyl-oxalate complexes serve as an example. The oxelate 1lon, 02042', has been propoeed by some :l.nvee.’t:iga‘t:oralflé&&2 88 the complexing ligand; the bioxalate lon, HC,0,, by othersi*l:116; ang He1at*2 nas (Text continues on pege 30.) 23 Tables V. Complex Formation with ‘IJA"" Ione - Urganic Ligandsd Complexing agent Methad T Hedlumn pK of HPL Log of equilibrium constant, Raferance remarks c:5rlao2 diat 25 0.1(010,") B.82 K, 8.6, X, 8.4, % 6. b 14b, 111 acetylacetone: HL Ky 6.1 n " n B.B2 K, 9.02, K, B.25, 13 6.52 14b, eof. 112, Ky 5.98, Py 17.27, B3 23.79 113 By 29.77 ' CgHl50pF5S Bp 25 - 0.1 K 7.2 114 thenoyltrifluoro- acetone HL C; oM 6% Ya. : L 2.21 K 25.6 115 Sy Lo e a0l 25 (Fy80,)(1) EL7 2.77 pRIEGE®* &2 KL + 28N 1.0 L EL?" 6.16 w3~ 10.26 a TAfter Bjerrum, Schwarrenbach, end 51116m, .reference 20, The data, wilth the exceptlon of reference 111, has been camplled by J. Gindler. Column one liste the empirical formula, the name of the ligand, and a formula of thea type HPL which defines the entity L in terms of which the equilibrium conatanta are exprassed. The ligands are placsd in order of thelr emplirical formula according to Dellstein's sysatem. Column flve li_nta the pK valuen (-103101() of the mcld-base equilibria involving the liganda and fer to the dlssoclat : b+l-p)= = HFL(\"'P)-' :nflp_ll,(b"'l'l’)' +at ; Km w [HpL(b-p) 'J The notation 1s sxplained following Table III. Tablé VI, Complex Formatlon with Uog"' Ions - Inorganio _T.isa.nd# Complexing agent Method T Medium Log of equllibrium constant, remaris Refarance Cyanoferrate{II), Fe(cfl)g' sol a5 var Eflo -13.15 65 Thiocyanate, ap 20 1(Nac10,) K, 0.76, K, ~0.02, X, 0.4 66 SCN” Bp 25 -0 K, 0.93 ) 67 Carbonate, prap aolid av U‘OzL_.l,t" 63 . coZ- sol sp? 25¢ O corr Ky 3.78 69 quoted in 3 ref. TO mol ap 257 O corr K[00,(0H) H,0(8) + CO,(g) wet TO,C0,(8) 63 + 2112o1a + + _ x.zfxpoxf (8% 1.82, xa/xpor.i-‘ wth) 1.1 63 AG 25 0 corr By 1h4.6, fl3 18.3 63 mp- ~2 Ey -3.5, ev (U’Oa)z_(OH)aL' 70 aol -0 X [Raf(vo ) 12,8 o -2.0 70 26 _ K.E/xpoxg(n*') : U0,C0,(n) + 2HCO] e uoe(coa)g" + Co,(g) + H,0 Ry/Rp E5(E') 1 D0, (00,)5" + znoo; W,(0,)3" + Co,(g) + B0 sol 25 1(ng,C1) By 22.77 n ap 0.3(kN05) . TEIDO,(00,)3" + B0, =2 U0,(00,) 0083 72 + Eco_;la.o sp -0 % 2.2 8p var x[uozwoa)zoo"' + 8t & 10,(c0,), 00E>"110.6 73 Nitrate, NOj sp 25 5.38(NaCloy), oK' K, -0.68 74 sp 25 T(RaCl0,), 28" K, -0.57 h X-ray so0lid av UOZL; in m:trozx..j(s) 75 qh 20 1({Nac10y) X, -0.3 T 16 dist 10-30 2(NaCl0,) K, -0.52(10°), -0.62(25°), -0.77(%0°) il fl_. Table VI. = Continued Complexing agent Phoaphate, FOj- Methed T ap ? ap 22-28 8p cond 25 oond 25 ap 25 so0l 25 aol 25 anl ex 20 s0l 19-20 ap 25 sp 25 dlast 25 anl ex 20 ap 25 Bp 25 Medium var org M0200 EtoH MeECO :LHClou 1HCth_ 1HC10)? 1H0104? 1HC1O), 1HC10, ]-!'3L vVar E3L var E3L dii di H3L 1 53L di1 ]-%L 4a11 molid: var Q nsorr yar 1.07(Na0104) 1.07{NaC10y) 0 aorr 1(010u') 0 Corr(%) Log of equilibrium constant, remarks Referenca no ev cpx: 150-fold exceag L 50 &v U0 Lq 78 Ky 3.6 in Me,CO : 79 12(?)3.15, K3(?)1.39 in EtOH 80 x2(7)3.96, xa(?)z.us in Me,CO 80 Itwog“ + HyL @ vogH, I** + (2-x)E*11.58 81 KID0S* + KL 2 00, | ¥ + (2-x)K*11.57 82,83 T xwm]lor?2 of. 83 R[D0Z" + 2T = 0, (H,L), + 2HYIL.18 E[U05" + 3H,L = U0, (H L) HL + 2B*12.30S K, (U0 HL(a) + 28% o wol* + H,11-2.65 K, [U0,EL(s) + x8" 2 voH, | 17%)-1.29 X=]1or?2 K [UofL(s) + HoL o= UOE(HEL)EJ-I.T I(’[UDQHI-(u) + 2H3L = UOE(HzL)EHBL]-O-SE R, [(00,)5L,(8) + 65" e 300EF + 2E.1]-6.15 K, [(U0,)gLy(8) + HyL + 3H' =3 300,H,L%)-2.50 Kp[(U0,) 3L, (8) + 4B L =2 300, (HyL),1-2.89 Eq[(00,)31,(8) + THyL = 300, (H L) H L1053 '*uoaflr.(u)“ - anrrro#(neo)q(g) av UOEEQL"', UOE,H3L2+, o, (8,L), 84,85 HEL' : K 3.00, K, 2.43, K3 1.90 86 HL : K <1.88, B, 3.86, B, 5.23 K, [00, (H,1)371-0.53, -2.27, -1.%8 Ea[UOE(l'%L)g"'J-l.BE, -1.18 (gt - K14 2-12) B, (V02 hr} 137)-26.36 a7 x (vo2*eL3)-23.11 24, 2- + K, (U0Z "HL=")-10.6T, (5" : K 12.44, K, 6.71, 113 1.96 ; 24 + av U02H2L+, O H L2, 00, (ByL) s UOGH L, 88 p(voZ*al; HI)i.15% 89,90 + o b B{Uog"'H_e(!-LaL)ell-Bll— 89,90 fl[trog“l-lfz(}%l.)au.ofi By, (003" + 1H,L = oS (1~gm L7 ezt 91 + (108" : K, 098, K); < 1.8, Ky 1,38, Kp1 2% Kpp 3-95 Ky 1.1, Ky 2.5%, %2 J'I'-Bl K33 5'3 H,__.L' : X 3.0, B, 5.5, By 7.4 H3L : Ky ¢ 1.8, By 3-9, 53 5.3 (same aa 11+ Bopr Kgg) (u* : K 4 2.10) K:r.:] T Kig O:Ts 1(11 0.8, Kao 0.4, K 1.4 88,cf, 91 (xt - K5 1.68) Kyy t K 1.1, Ky 1.2, Ky 1.3, Ky 2.2 88,cf. 91 (B : x4 2.10) same equilibrium reectlon, different notation mame equilibrium reaction, different notation same @quillibrlum reazocotlion, different notation le o l@ Table VI. ~ Contimed Camplexing agent Method T Madium Log of equilibrium constant, remarks Reference Polyphosphate, pH 25 Al n~5:K 3.0, or B, 6.0, or Py 9.5 92 [Pn°3n+1] (n-2)- Arsenate, AsO3~ sol g1 20 var x,(voZt m2")-10.50, K (003"L1*L*")-18.82 g3 X, (v02*Na*13")-21.07 X, (vo2te*t3")-22.60, X (00Z*Nm,*L3")-23.77 (6" : K, 11.53, K, 6.77, K4 2.25) Sulfite, sog' 8p ver ev T0,LS", strong epx 94 8ol 25 (m4)2m3var xao-a.'59 a5 By 7-10 Sulfate, 50§ 8P 25 2.65(Kkacioy), 28" K, 0.70 74 25 3.5(%), =8 K, 1.83[K, (¥9)1.125) 74, cf. 61 qh 20 1(NaC10) K, 1.70, K, 0.84, K 0.86 96 p(003 1% 207) 3.78 B(0031L3"20") .60 8p 20 1(NaC10y) K 1.75, K; 0.90 96 cond 25 0 corr Kl 3.23¢% g7 dist 10 2(KeC10,) K 1.80, K, 0.96[K, (E")1.01) 77 atet 25 2(NeCl0y) X, 1.88, K, 0.97[K (E1.08] 77 4H, = 2.3, AH, = -0.9, A8, = 16, A8, = 2 dist 40 2(Na010,) K, 1.93, K, 0.93[11(3*')1.17] 7 anl ex var ey UOELg", U205Lg' 93 ani ex 25 var ov UO,L, T0,L2", uozxg'. U205L;' 99 8p 25 -0 E, 2.96, 12 -1 67 Fluoride, F~ anl ex 25 HCl var 'k, 1.18 100 K 4.32 100, o£ 101 ap var K, 5.5, By =B 101 8p ~0 UOF, var "Ry (200,F, = (U0,R,),10.18 35 qh 20 1(RaC10,) K, 4.59, E; 3.34, X, 2.56, K, 1.36 (K, (Eh)2.94] 102 cond 25 0 aorr EE ~Lk. &k, gv other opx 103 dist 10-§0 2(NaClo,) K, 1.78(10°), 1.42(25%), 1.32(%0°) 77 25 2(NaC10,) A= 514, a'8,= -2 77 atst 25 C(NaCiOy) "k, i.32(c=2), 1.43(c=1), 1.38(0=0.5), 77 1.57(C=0.25), 1.71(C=0.05) cfug 0-30 UO,F, var xyp 0.48(0%), 0.85(30°) 16 ‘qh 20 1(Fa)Clo, K, 4.5% K, 3.3%, K 2.57, Ky 1.3% 102, 104 tK, (5%)2.93], no ev polyn opx for < 0.1-005" of. 104 Chlerids, C1~ qh 20 1(Nacloy) X, -0.10 76 sp 20 1(NaC10,) K, -0.307 76 pol sp gl 25 0O oorr 1& Q.38 105 "dist 10-h0 2(HaCl0,) X, -0.24(10°), -0.06(25°), 0.06(40°) 7 25 2(NaC10y) AR, = 3.8, AS; = 12 77 anl ex 25 HC1 var ev anl opx in > 0.5M - HCl 106 25 0O corr K, -0.1.°K, 0.82, K, -1.70 106,c£. 107 sp 25 -0 K 0.21 67 ap e var no ev opx : 150-fold exscaesa L~ 50 sp e, 00 ev UO,LY, UO,L,, 0,15 ' 108 Perchlorate, ClO;- ap 25 2-6 010; no ev c¢px 109 Bromide, Er~ gh 20 1(¥aCl0,) K, +0.30 76 Table VI. - Contlrued Complexing agent Todate, 0, ap 8ol gol Mathod Medium 25 -0 25 o.e(NHun) 60 q.z(mucl) Log of equilibrium constant, remarkas Rafesrence - K -0,20 67 X, -7.01, B, 2.73, 53 3.67 110 1!0-6.65, 52 2.74, flj 3.44 110 Z after Bjerrum, Sohwarsenbach, and 91llan, reference 20, Dates which appeared in the literature prior to the middle of 1957 haa been campiled moatly by the above authora. The notation 1s explained following Table IIT. Complexing agent C2H20u oxallc acid:HEL C2H402 acestic acid:HE 02Hu03 giyeolie eeld:HL C2H30201 Subfequent data has been campiled by J. Gindlep, Table VII. Complex Frmation with Uog"‘ Ions - Organi¢ Ligands® Methed Pt oat ex cat ax cat ex 22,050, AgoCo0y AECx0, 801 gol sol oat ex oat ex 801 Bp gl ap gl sp gl emf sp pol cat ex 1on ex gl cat ex emf T 25 25 20 20 20 25 25 25 20 25 RT 25 25 20 Medium PK of H I Log of equlillbrium oonstant, Reference ¥ remarics 0 eorr H,L 1.27 K, 5.82, X, 4.7%, HL : K 2.57 49 HL™ 4.29 0.16HC10;, H,L 1.28 HL™: Ky 3.40, K, 2.56 116 HL™ 3.75 1HC10, HyL 1.28 HL™: K, 2.83, K, ~1.85 116 ZHC10, HyL 1.28 HL™: K 2.89, K, ~1.85 116 0.069 *KI'(UOE)ELE' + oL = (U02)2L5']4.‘+2 117 0.022 *x 1.60, ¥&[(Uo )18 + I2° ’ 2 3 2(uo,L,)%711. 32 117 K[E(U02L2)2- I e (Uoz)zfig'ls--‘?fil 0.008 ¥ 0.lg 117 ver B,L 0.97 E 6.77, E, 5.23, B, 12 118 HL™ %.19 Klwo5t + AL = UoL + 21*11.60 24 2= -+ 1':[11‘212 +22H2I'.' = UDELE + AF"31.68 HC10y, $1.54" X, [002*L ~(H,0)41-8.66 118 ANO;, > 1.5H" K, [uo3* L2'(l-220)3]-8.52 118 1HC10 K, 6.58 graphically, 6.%0 anmlyti- 4 1 116, af cally, By 10.74 118 2HC10, K, 6.92 116,cf 118 =0 K 6.00, K, 5.08, 3. 44 (pre- 119 ferred value) ! 0.312 Ky 2.1 1zo0 . 0.05 K[200L + Hy0, =2 (U0,L),(00)2" + 2nti-1.62 120 0.312 KI2U0,I3™ + HyOp i (U0,),(00)18™ + 28%]-3.66 120 121 1NaCloy 4 .59 K, 2.38, K, 1.98, 13 1.98 2 NaL-HL K, 2.63, K, 2.03, Ky 1.60 64 buffer 0.16({NaC1) K, 2.38, Pq €.36 122 . . 123 0.5(Nam3) 1% 1.22, B, 5.89 , 1NaClo, 3.58 X 2.ha, K, 1.54, X 1.24 12 0.16(¥aC1) K, 2.78, K, 1.30 116 0.16-0.19 K, 2.75, K, 1.52 116 1 1NaClo, 2.66 K, 1.hg, K, 0.85, 1!3 0.51 25 a7 Table VII. - Continued Complexing agent Method T Medlium pK of H L Log of equilibrium constant, Referance P remarks chlorovacetlic acid:HL sp 20 1Na0104 2.66 Kl 1.98, Ka 0.80, K, 0.37 125 C H 0N atet 25 0.45(NeCl) HLT 2.32 K 1.43 ) lee glyolne:EL pH 1.90 C,AgON, pH 25 0.15-0.25 HL' 8.06 K, 5.15 126 glvolne amide:L C4HgOy Bp RT ev U03*/L opx in retic 1/1 pf 3.5 127 laotio eeld:HL sp,pi RT av Uo,':,'*'/r. opx in ratio 1/1 pE 6; 128 presupposed dimerization CH 05N diet 25 o.45(rac1) ELF 2.21 K o.67 116 serina:HL pH 2.05 CyHgOg Bp RT ey Uog"'/mu:l.a.te ofx in ratio 1/1 127 malic acid:H,L and 2/1 pH 3.5 ep,PE RT ov U03*/malate opx in ratio 1/1 as 128 dimer poid solution; 3/3 and 3/2 pH ~8 CyFeO¢ 8D RT ov UOS*/tartrate epx in ratio 1/1, 127 tartaria acid:H L 2/1%, and 3/1 pH 3.5, 1.6 ap,pi RT ev U05*/tartrate cpx in retic 1/1 as 128 dimer geid solutlon; 3/9 and /2 pE -8 C5HgO, gl 30 -+ 0 B.95 K, 7.74, X, 6.43 129 acetylacetone:HL. gl 10 -0 9,10 K, 7.94, 12 6.53 129 dist 25 0.1(c10;) 8.82 K, 6.8, X, 6.3 51, 111 K[005*+ 1™ + HL = voL(r) 8.7 K[D05*+ 217 + HL. ¢\ UO,L,(HL)114.8 ap 25 BtOH ‘HL : Ky 2.43 BO CeEqOg op,pE 20-21 0.1(KaClo,) E,L ¥.07 HL™ : K 2.48 110 ascorbic acid:(HaL) pH 2-3 CgHgOy »p RT (MaCl) ev U02¥/citrate opx in ratio 1.1 citric acld:HyL and 2/1 pH 2-6 131 pol 30 ev Uog"'/uitmte cpx in ratio 1/1 present as dimer pH 4.6 132 gp,pi AT : ev 005" /ottrate opx in retio 3/3 and 3/2 pH B 128 ap,pi ¥ var A3 K, 3.165 pE 4-7 ' 133 cond ev UOZHEL” & U0,IE™ + BY pi 3.6 av Uog"'/citmte epx in ratio 2/3 pE T7-9 g 25 0.15(%) HL 2.9% H27: K 8.5 134 1-13L' k.3h 112" 5.62 CeigOoNy pH 25 0.15-0.25 EIY6.17 K 7.17 . 126 histidine :HL HL 9.20 073602 ap ¥ 50% EtoH K, 1.81 urenyl acetate, 135 salicylaldehyds :HL acetlic acid present, pH 3 ver Bo 2.63 urenyl nitrate, pH 5 C:..’,J-ISO3 =p I'.I. 13. 4 136 sallcylic acld:H,L dist 25 0.1{NaC10,) H,L 2.82 HL™: K 2.2 138 HL™ 13 -X[003% + HL™ + OB @ U0,{HL) (0H)112.1 Table VII,- Contilnued Complexing agent Method T Medium pX of HpL Log of equilibrium conastant, Refarenca remarks c.THEo4 gl 30 50% dioxan 9.40 K 10.1, x2 7.3 139 koJle acild:HL Cg06S ep 25 =0.015 K L™ 2.86 HLZ": K, 3.89 130 5-gulfosalicylic acid:HaL 071-:.?.02}: D 8.09 K, 6.40, X, L.g7 14 salicylamide :HL CoHy10,N, pH 25 0.15-0.25 HL?* 5.38 K 5.76 126 histidine methyl 't 7.93 eater:L CgHeON, gl 20 50% aloxan HL' 1.77 K, .68, K, 7.16 142 8-hydroxycinnoline :HL 0.3 NaClOu HL B.84 CqHEON, gl 20 50f dioxan EL' <2 X, 8.4, K, 7.51 142 5=hydroxyquinoxaline:HL 0.3 Na.C104 HL 9.29 CgTeON, gl 20 50% dloxan H2L+ 3.30 X, 8.99, K, 7.70 142 8-hydroxyqulnagoline:HL 0.3 Na.Cth_ HL 9.59 CaHgOs dist 25 0.1(NaC10y) 3.69 1c[uo§,+ + 17 + OE" &= Uo,(L)(0H)111.9 138 methaxybenzolio acid:HL CgtON gl 20 50% dloxan H2L+ 4.4 K| 11.25, K, 9.6% 1y 8-hydro inolire 0.3 NaC10, KL 10.80 (oxine) :HL dist 25 0.1 fq 23.76 143 CgHgON, gl 20 50% dloxan 32L+ 2.59 K; 9.00, K, 7.30 132 B-hydroxy-4-methyleinnoline:HL. 0.3 NaCl0, HL 9.00 CgH, 0y NS PR, 8p 25 0.1 KNog HyL 3.84 K, 8.52, K, 7.16 14 8-hydroxyquinoline-5-sulphonic acid:H,L HL™ B.35 K[UOQ(OH)LE- + 5 - UozLa"] 6.68 K[(er(OH)La)g' + i g 200,127 111.7 K[200,(0H)L;" (UOE(OH)Lz)g'Jl.T €y gHgOR g1 20 50% dloxan H,L' 5.01 X, ~9.4, K, -8 142 8-hydroxy-2-methylquinoline:HL 0.3 Na.Clou_ HL 11.01 C1 oHgON gl 20 50% dloxan I-I2L+ L.71 K 11.25, 9.52 12 8-hydroxy-5-methylquinoline:HL 0.3 NaCloq_ HL 11.11 01 gHgON g1 20 50% dioxen H,L® 4.76 K, 10.89, K, 9.26 142 6-hydroxy-5-methylquinolire:HL 0.3 NaC10, HL 10.71 0, gHlgON gl 20 50% dioxan H2L+ k.26 K 11.28, K, 9.78 142 B-hydroxy-T7-methylquinoline:HIL. 0.3 NaCqu_ HL 11.31 C1 ot o0, gl 20 50% dloxan H L' 3.15 K, 8.77, K, 7.33 142 8-hydroxy-2:L-dimethylquinazoline :HL HL 10.1% €y gFy 50N gl 20 S5of dioxan H,LY 5.4 K 10.10, X, B8.20 142 1:2:3:4-tetravydro-9-hydroxy- acrldine :HL 0.3 NnClOu HL 11.39 ¢, oHy 5CN, g1 20 50% diaxan EL" < 1 K, 8.53, X, 7.85 142 8-hydroxy-4-methyl-2- phernylquinagoline :HL 0.3 NaGlOu HL 11.33 CeaH23°9N3 ap 25 var (mh)z}fl' “(%): 5 L.77 145 ammonlum a.urintrio.a.rboxi’late (eluminon reagent) :(N‘Eu)HEL -2 pfter Bjerrum, S&hwarzenha.ch, and 311ltn, reference 20. Date which appeared in the literature prior to 1956 has been compiled moatly by the above authors. mbsequént data has been complled by J. Gindler. The notatlon l1m expl_a.j.nad following Tablee TII and V. 29 atated that a complex 18 formed wlth undlasoclated oxalic acld, Heceou. In more recent work, Moskvlin and Zakharovallg conclude that complexes may be formed with both 02042 and Hcaou' 1ons and that the amount of each formed will depend upon its stabllity and the conditions of the experiment. The compoaltlon of a complex 1s sometimes declded upon by comparison with complexee having simllar liganda. For example, I-Ic‘ilfc-BeJ:-ne.t'}:r'om-,;"--zg in her work with salicylic acld, H,A, and 2 methoxybenzolec acld, HB, wase able to show that complexes of the type U0, (H,A) (HY) , UO2(H2A)(H+) _5» and U02(HB)(H+) _p Were formed in the agqueous phase. (The negatlve subscripts indicate that H™ was eliminated in the formation of the complex;) The experimental data for methoxybenzolc acld was approximated by asguming only the complex UOE(B)(OH). For sallcylic acid, the complexes U02(HA)+ corresponding to U02(H2A)(H+)_1 and UOE(HA)(OH) or UO,A corresponding to UOE(HEA)(H"')_2 were postulated. It was not poeslble to distingulsh between the latter two. However, from Cthe simllarity of the distribution curves found for the two aclda, it was suggested that the sallcylate complexes are formed by HA™ ligands. A vast amount of work other than that listed in Table VII has been done on the preparation and identificatlion of organic uranyl complexes. Some of the complexing agenta studled recently include dilhydroxy-malelc acid,lflg trioae-reductonelig#lég (enoltartroneldehyde), reductic acld=2t (eyclopentene-2-dlol-2,3- one-1), complexoneslfigiléi (1iminodlacetic acid and its derivatives), xanthates and dithiocarbamates,lé& 1:>I-0'|:opor-phyr-:l.n,l—i2 o-cresotic acid,léé miricitrine,lEI dialkylphosphoric acids,lég&lég and pyrazolone derivat-ives.lég 3. Non-aqueous solutlions of uranium. Solubility studles. A number of uranium salts are soluble in orgenlc solvents. Uranyl nitrate 1s the'notable example. Ag the hexahydrate, this salt 1s soluble in a 30 varlety of ethers, eaters, ketones, alcohola, aldehydes, and substituted hydrocarbons.161'16 The followlng generall- zatlons have been madeléé concerning 1ts solution 1n organlc gsclvents: (1) In a given homologous series, the solubllity decreases as the molecular weight of the solvent -il.ncreaaea.161 16 (2) Solutions occur~w1thtl§2 Ethers: aliphsatlic ethylene glycol dlethylene glycol saturated cyclie Acetals Ketones: aliphatic aromatlc alicyclic mixed aliphatlic-aromatic Alcohols: aliphatlc allecycllce Varlious esters Nitrogen-contalning solvents: niltriles aromatlc basea (3) Solutione do not occur with: Hydrocarbonsléi Ethers:léé aromatlc unsaturated cyclic Sulfur-conteining solvents.lég Glueckaufiéé has made the phenomenologlcal obeervation that a plot of the solubllity of uranyl nltrate against the oxygen-to-carbon ratio 1n the solvent molecule results 1n a silngle curve for alcohols and ethers; but in a double curve for ketones; one for symmetrlic and one for asymmetrlic ketones. Tonization. The quantity (An/constant)* hae been used by McKay and co-workersléz:lég to estlmate the degree of lonization of uranyl salte 1n organlc sclvents. By this criterion, uranyl nitrate 1n concentrations of 0.01 - 1M 1s * A = molar conductlvity. T = vlacoslty. The constant 60 1s used for 1:1 - electrolytes; 120 for 1:2 - electrolytes. 31 substantially unionized 1n water-saturated solutlons of ethers, ketones, alcoholes and tributyl phosphate? Only 1n saturated diethyl cellosolve and 1n 1sobutyl alcochol is ilonizatlon 1n excess of 10%. The large amount of water whilch dlssolves in the latter solvent may account for this. In tributyl phosphate, the dissociation of uranyl nitrate increases as 1ts concentratlon 1n the organlc phase 1s de- creased. At 10'5E-the salt 1s approximately 40 per cent dissociated,lég i.e., An/120 = 0.4 Uranyl perchlorate at this concentration is almost completely ionized.lég Lon associatlon occurs at higher concentratibns, but elgnificaently less than for uranyl nitrate. At approxlmately 0.01M, the assoclation of uranyl perchlorate 1s maximum (An/120 has a minimum value of —0.1) in the concentration range 107 to 1M, The lonizatlion of this salt may well be assoclated wlth the amount of water contalned withlin the tributyl phosphate since the electrical conductivity 1s decreased by dehydration.lég Jezowska - Trzeblatowskae and co-wc':rkersEg have measured the molar conductivity of uranyl nitrate in organlc solvents that contaln only water from the hexahydrated uranyl saltf* The conductlvlity was found to be low and to decrease wilth a decrease of the dlelectric constant of the solvent. Conductivity measurements of UCl4 iIn methyl aleohol indicated the salt to be somewhat dissociated.gg- The ‘dissociation was found to increase on additlon of tributyl phosphate. Kaplan, Hildebrandt, and Ader=lC have classified into Solvents tested other than tributyl phosphate: diethyl ether, dlethyl cellosolve, dlibutyl carbitol, methylisobutyl -ketone, 1gobutyl alcohol, and lsocamyl alcohol. **¥30lvents tested: methyl alcohol, ethyl alcochol, acetone, ethyl-methyl ketone, methyl 1lsobutyl ketone, acetylacetone, stannous chleoride 1n acetone. 32 types the abaorptlon spectra of uranyl nitrate in a number of * solvents and solvent mlxtures. Differences between types were attrlibuted to a serles of hydrated and solvated nltrate complexes, UOZY , UO N0, UOL(NO The 2773 ° 3)2’ 3)3-' relative concentrations of the complexea depend upon the nature and er(No of the solvent, its water content, and the concentration of added nitrates. It 18 1lnteresting to note that the absorp- tion Bpectrum of uranyl nitrate in tributyl phosphate (0.016 - 1.6 M) is characteristic of the complex UOE(NOB)Q and indicates 1lttle ionizationjlég A simllar spectrum 18 glven by uranyl nitrate 1n methyl 1sobutyl ketone (0.02 fl)fzg Uranyl perchlor- ate 1n methyl 1sobutyl ketone (0.02 M), however, exhibite a spectrum characterigtic of the uranyl ion, UO‘%+ . These results appear to be 1n general agreement wlth those obtalned through conductivity-viscoslty measurements.léz:lég The trinltratouranyl complex UOE(NO3)3- hes been studled by a number of workersZgiIgi&Zl;lZi It 18 formed by the additlion of a second soluble nitrate to a solutilon of uranyl nitrate in a non-aqueous solvent such as anhydrous nitrilc &s.ciLd_,-:I—'Zl dinltrogen tetroxide,llg acetone,zg---’—Ig methyl l1sobutyl ketone,Ig dibutyl ether,lZi etc. Kaplan and co- workeraIg also report that the complex 1s formed in 16 M nitric gcid, but that 1td formation 1s far from complete. The negative character of the complex has been demonstrated by electrolytlc transference exper-iment:st.—'?-g Its composition has been deduced by the 1lsolation of solld compounds from golutlons of the type descrlbed abovez-g--’—-JlZl’—Ezg end by the gimilarity of the abeorption spectrum of such solutlions with that of erystalline cesalum uranyl nitrate,CsUOz(N03)31§112 *Spectra clasgifled: uranyl .nltrate in water, acetone-water, dioxane-water, n-propanol-watér, ethanol, chloroform + 0.7% ethanol, pyridlne, acetlc acld, ethylacetate, tetraethylene glycol dlbutyl ether, nitroethane, methyl isobutyl ketone, cyclohexanone; uranyl perchlorate 1n methyl 1sobutyl ketone. 33 The stahllity of the complex depends upon the nature of the essociated cation as well as the nature of the solvent and the prepence of water 1n the solvent. The general order of the solvents with respect to stabillity of the trinitrate complex 1s: ketone > ether > alcohol > water£1§ The formatlion of chlorouranyl complexes 1n neon-&queous solvents has been reported by Vdovenko, Lipovskii, and NikitinssC® The complexes U0201+, U0,CL,, U02013‘ were formed by the additlion of-pyridine hydrochloride or hydro- xylamine hydrochlorlide to a solution of uranyl perchlorate or uranyl chlorlde in dcetone. The Btablllity of the tri- chlorouranyl complex wae found to be dependent upon the amount of water present 1n the solvent. A compound wae separated and ldentifled es (C5H5NH)2U02014. Hydration. In partltion studles of uranyl nitrate between aqueous solutlion and organilc solvent (alcohols, eatera, ethers and ketones) 1t 18 generally found that the water content of the organlc phase lncreases with uranyl * nitrate concentration.16 167 For alcohols, the relation between the water content Mw and uranyl nltrate concentration Mu appears to be a complex function.** For esters, ethers, and ketones the relation 1s linear except posslbly at high values of Mu. This reletlon may be expressed M, o= Mo+ hM . The quantitles are expressed in terms of molallties of the dry solvent. M; 18 the solubillity of water in the pure gsolvent; h 1is a conatant. The siope of the line, h, repre- * The water content of alcohole may decrease Inltlally as the uranyl E%trate concentration is 1ncreased from O to 0.1-0.2 molal,1067 . * % . " Katzin and Sulliva.nz‘-§1 report a linear relation.bfg een M _and M; for lsobutyl alcohol. McKay and Mathleso point oUt that If the deta of Katzin and Sulllvan at low M, are glven significance, then & more compllicated relationshlp between the two quantltles exlets. 34 sents the degree of hydration. For many of the linear solventa h is very nearly 4.0.16. 167 This hae been inter- oreted by Katzin®l* to mean that the specles U0, (H#,0),, (NO is extracted. McKay,lZé however, conslders thls to be a 3)2 nean hydration number; that a serles of hydrates are presént ranging from the dl- to the hexahydrate; that these hydrates are 1n equllibrlum wlith each other-and'are of comparable stabillty. The latter view ls supported by 1isoplestic neasurements.izg Infrared measurements on ethereal and ketonle solutions* of uranyl nitrate, lndicate two moleculea of water to be strongly bound to the uranyl nlitrate and the remainihg water molecules to be more weakly bound.lZZiEIQ The extraction of uranyl nltrate from an agqueous system into tributyl phosphate (TBP) causes the displacement of water from the organle phase.lég The displacement 13 roughly linear with h being -2.l§§ This 1e 1n agreement with the formulae TBP'H,O and UOE(NO3)2'2TBP.E§§ Uranyl perchlorate, however, apparently does carry some water into tributyl phosphate.lég Whether thls water 1ip assoclated with free uranyl lone or unionized U02(0104)2 1s undetermined. Solvation. The isolatlon of solvated uranium salts, in particular uranyl nitrate,ls reported 1n the 1iterature.§9 163,180-182 In phase studies of ternary syetema: uranyl nitrate, water, organic splvent, Katzln and Sullivanléi_ have concluded that uranyl- nitrate 1n aqueous solution is largely hexasolvated, subject to the sctlivity. As organiec melecules are dissolved, 2,3,4 and perhaps 6 water molecules may be displeced, depending upon the electron-donor capabllities of the orgenlc moleculea. The total solvation 1e a functlon of the actlvity levels of the water and organlc molecules, * Solvente studled: diethyl ether, acetone, methylethyl ketone. 35 If a particular confilguration is stable enough, 1t may survive as a crystalllne sollid. The particular stabllity of the final two water molecules 18 in agreemept with the resulta of Ryskin and co-workerslzz&lzg obtalned through infrared abporptlon meapurements. The abllity of solvents to dlsplace water 1s in the order: alcohols > ethers > ketonee.lgi This general order of solvate stablllty 1s confirmed by heat of soletion measurements.léfi It 18 in gsgreement also wlth the order of base (electron-donor) strengths of the solvents determined by other means.léé&lgi' Methyl isobutyl ketone 18 anomalous 1n that 1t behaves stronger toward uranyl nltrate than its base strength would indicate.83:183 Priputyl phosphate, according to heat measurements, competes with water almost as well as dlethyl ether and 1sobutyl a100h01el§§ The order of solvents with respect to solvate stabllity 1s opposite to that with respect to the stability of the ftrinltratouranyl complex. Thls Buggests a competitlion be-~ tween solvent molecule and nitrate lon for coordlnatlon wlth the uranyl 1on.lI; Feder, Ross and V‘cvgellgi have studled the stabllity of molecular addltion compounds wlth uranyl nltrate. The com- pounds were prepared by shaking uranyl nitrate dehydrate wlth varioug addenda in an lnert solvent: benzene and/or 1,2- dlchlorcethane. 1l:1 moiecular addlition compounds were found with uranyl nitrate and ethyl aleohol, n-dodecyl alcohol, tetrahydrofuran, propylene oxide, mesltyl oxide, tributyl phoaphate, and N,N-dibutylacetamide. 1:2 compounds were observaed with uranyl nitrate and acetone, methyl lsobutyl ketone, cyclohexanoné, ethjl acetate, 2,4-dimethyltetrahydro- thiopene 1,1-dloxide, B-chloroethylacetate, ethyl chloroacetate, ethyl cyanoacetate, dlethyl ether, allyl alcohol, ethylene chlorohydrin, and acetonltrile. Formation constants were determined from changes 1n the aolubllity of urenyl nitrate. 36 It was shown that the stabllity of the addltlion molecules, for those addenda having simllar functional groups, was 1in agreement w%th the base strength of the addend; l.e., the more s8table the molecule, the greater the base atréngth df the addend. The average number of solvate molecules n assoclated wlth uranyl nitrate 1n 1ts partition between water and varicus organlec Bolvents* has been Btudled by McKaylgéngg and co-workere. The value of n was found to vary wlth the uranyl nitrate concentration of the organic phase. For most of the solventa studled, n varled between 1 and 4. For cyclohexane, considerably larger velues were found for low uranyl nltrate concentratlions. A saturated Bolution of uranyl nitrate hexahydrate i1n trlbutyl phosphate corresponds closely to the unhydrated 3)2'2TBP.£§-§J—-]-'gI Evldence for the exlstence of the Blngle specles 15:168 18 disolvated compound UOE(NO (1) The solubility is not appreclably temperature dependent over the range 0-50°C. (2) On freezing and rewarming a saturated solutlon, a sharp melting-point of -6.0 = 0.5°C 1g observed. (3) The mole ratio of uranyl nitrate to TBP approaches the value 1:2 asymptotically under a varlety of condltions. (1) The effect of inert dlluents for the TBP on uranyl nitrate partltion coefficlents supports a 1:2 formula? l.e., the partltion coefflclent of uranyl nitrate varles as the square of the TBP concentration. | The experimentel conditlionsa under whlch Feder, Rosa 184 and Vogel—— reported the formation of UOQ(NO *TBP were 32 congiderably different from those of Healy and McKay.lég »* Organlec solvents studled: diethyl ether, diisopropyl ether, dlethyl cellosolve, dlbutyl cellosolve, dlbutyl carbitol, penta-ether, lsoamylacetate, methyl 1sobutyl ketone, cyclo- hexanone, 37 Jezowska - Trzeblatowska, 33_5129 report that the absorptlon spectrum of uranyl nitrate 1n tributyl phosphate glves no 1ndication of the formatlon of a stable complex. Attempts to ldentlfy a complex specles in the concentration range 0.02-0.06M were unsuccessful. Heaford and McKay-1§2 report evidence for the formatilon of U02(CIM)232TBP under certain conditions. From & 10.3M aqueoul perchloric acld solutlon, the partitlon coefficlent of uranium varles as the square of the TBP concentration 1n benzene. Under other conditlions, other solvates may be formed. Jezowska - Trzeblatowska, gg_glgg report the formation of a 1:1 complex between U014 and TBP in methyl alecchol. Tributyl phoBphlne oxide, 1like tributyl phosphate, forms an anhydrous disolvate wlth uranyl nitrate.lgl Healy and Kennedylgg report & number of other neutral organophoa- phorus solvents which form solvates with uranyl nitrate. Most, but not all, of the solvates reported are anhydrous. A1l of the solvents extract uranium from aqueous solutlon in proportlion to the square of the solvent concentratlon (in benzene). However, not &ll solutions of the soclvent in benzene and saturated in uranyl nitrate give mole ratios of solvent to uranium of 2:1. For the two diphosphanates and one pyrophosphate studled the mole ratlos were l1l:1. This may be indlcatlve of chelation or polymer formation. The mole ratio 1n triphenyl phosphate wag ~22:1. This 18 probably the result of the solvent belng unfible to.displace water from the coordination sphere of the uranyl 1on.l§§ Solvate formatlon. between uranyl salts and acld organo- phosphorug compounds, eg. mono- and dl-alkyl phosphorlc acids hes been the subJect of Bome investigation.ao 158,1 188 1:1 complexea between uranyl nitrate and mono- and di-butyl phosphate and mono- and dl-amyl phosphate 1n ethyl alcohol have been reported.ég In explanation of diatributlon data 38 in conjunctlon with 1soplestic and vliscoslty measurements, | Baea, Zlngaro and Colemanlég have hypotheslzed that uranlum (VI) 18 extracted from aqueous perchlorate solutlone into n-hexane solutions of di-{2-ethylhexyl)-phosphate, HL, as the specles U02(HL)2L2. As the uranium concentration of the organic phase 1s Increased, there 1s strong evidence that polymerlzation occurs.lfig Similar-conclusions have been made by Dyrssenlig on the basls of the distribution of uranlum (VI) between agueous perchlorate solutilon and dibutyl phos- phate, HK, in chloroform. In hexone, the species UOE(HK)EK2 and U02K2 have been 1dent1fied.l§2 The extraction of uranium (VI) by dibutyl phosphate from aqueous niltrate solutions into benzene has been studled by Healy and Kennedy.-]:gg In addiflion to the specilesa UOE(HK)2K2, the polyuranyl specles (UOEKE)erK and the nitrated speciles UOE(NO3)2 + 2HK have been postulated to explaln the shape of the extraction curve as a function of nitric acid concentration. It has been postulated that the formatlon of mixed sol- vates or solvated chelates enhances the extractlon of uranium into certaln solvent mixtures. These systems are dlscussed in a lzfer section on solvent extraction. IV-D Separation of Uranium A number of review articles have been written on the analyti- cal chemistry of u::-:amium.é-f-flai-'-iggz-g-99 These, together with many texts on chemlcal analysels (see, for example, references 201-209), gerve well a3 guldes to the separatlon and purlfication of the ele- ment. More specislized surveys have been made by Hechfiglg on the quantitative micro-analjsis of uranium-bearing minerals, and by Law:r*c»lwEsbcfll.g-ll on separation processes for the recovery of nuclear fuels. Two general technlques are avallable for the separatlon of uranium. {1) Uranlum 18 removed from solution in the presence 39 of contamlnants by preclpltation, solvent -extractlon or some alternative method. (2) Uranium 18 kept 1n solutlon and contam- inants are removed. These techniquee are facllitated by the fact that uranium i1s reasonably stable 1n two oxidation states, (Iv) and (VI), and that complex formatlon may be effected to prevent the removal of elther uranium or contaminant from solutilon. In the fellowlng paragraphs, the Beparatlon of uranium by precipitation, solvent extraction, and ion exchange are deacribed 1n zome detall. Reference 18 made also to other methods of separa- tion: chromatography, electrodeposition, volatilizatlon and pyrometéllurgy. 1. Precipitation. In classical syetems of analysis, uranlum 18 & member of the third group of elements.* That 1s, 1t 18 not precilpitated by hydrochloric acld or by hydrogen sulfide in an acidiec solutdon, but 1t 18 preclpitated by ammonium hydroxide or ammonlum sulfide (see references 204, 206, 208, 213). Unfortunately, for the separation of uranlum, many other elements also are preclpltated by the same reagents. However, there exlate a large number of reagents capable of preclpltating uranlum over a wlde range of pH. These, combined wlth Judiclous use of the two oxidation states and/or the complexing abiiity of uranium, mey be used to provlide reasonably pure uranium deposita. Preciplitants. With the advent of nuclear energy as a source of power, numerous preclpltants have been investl- gated 1n an effort to find one speciflc for the separation and/or determination of uranium. None have been found to date. Waregli hag summarlized early work using organlc rea- * ~ In the system outllined by Noyes and Bray 292 yranium is precipltated 1n the sixth group wlth ammonium hydroxide and 18 converted to the sulfide wlith hydrogen sulflde. In the system of West and Parks,2l?2 uranium 18 precipltated in the fifth (basic benzoate)group. 40 gents a8 preclplitants. Shegli and Baileygié have investigated aome of the more promlslng onea. Rodden and Warf-ii have discussed the use of many reagents, both inorganic and organic, and have descrilbed procedurea for the use of many of them. The latter preclpitants, 1.e., those for which proceduree have been given by Rodden and Wa::-f,--?fi are denoted by a dagger (t) 1n the foliowing discusslon. Inorganlic preclpltants. The reagents are 1isted-alpha- betleally according to anlon. Arsenates.* Argenlce acld and ammonlium, sodium and potasslium arsenate preclpltate uranium as uranyl metal arsenate. Silver, tltanium, zirzonlum, thorlum and lead interfere. Separation 1s made from the alkall metals, alkallne earthes, aluminum, 1ron (TI), and rare earths, including trivalent cer:l.um.ii Carbonates.G’63;201,204,206:217-224 Precipitation of uranium with ammonium, sodlum, or potasslum carbonates 18 not very satlsfactory. Highly soluble carbonate-uranyl complexes are formed. Under proper conditions,the metal uranyl -tricarbon= ate saltse MuUOéC03§are formed. The solubllitles of the respective ammonium, sodium, and potasslum salts Iin water are 50(15°c),2—2£ 150(RT),@5 and 71(18"0)2—1§ grame per 1liter. The solubllity of the potassium salt in a 50% solu- tion of potasslium carbonate 1s 0.200 grams per liter.ggl The solubllity of the sodlum salt 1ls decreased by lncreaslng temperature and by lncreaslng sodlum salt coneentration,ggi Te¥ak2il has studled the precipltetion of uranium by ammonium and sodium carbonate. From a 0.043N uranyl nitrate solution, preclpltetion was obBerved to be maxlmum 1n the region of 0.1N precipitant concentration. Two maxima were observed for ammonlum carbonate; one for sodium carbonate. Above and below these falrly narrow reglons of precifiitant concentration, uranium enters into solutilon. 4] The uranium (IV) salt, NaGU(CO3)5 * 11H,0 1s preclpltated from reduced carbonate solutions at hlgh uranlum and carbonate concentrations.éé Barium uranyl carbonate salts are reported to be very 1|.m5=.olub1e.-6---:'1 However, 1ln the presence of carbonate solutions the alkallne earth salts are unstable according to fthe reaction,éfl MaU0,(C05) 5 (5 + 2co§' = [002(003)3]4‘ + MCOZ (.. Tezakgll has found the preclpltation of uranium to be nearly complete when the barium:uranium ratio is greater than 600 and the excess carbonate 1s leas than four times the barium concentratlion. A suspenslon of barium carbonate may be used to pre- clpltate uraniumrgfliggé Ammonium salts 1nterfere. A suspension of baslc¢ zin¢ carbonate may be simllarly used.éfliggz Iron, alumlnum and thorium also precipiltate. Cyanides. Alkall cyanides form a yellow preclpltate when added_to uranyl solutiona.éi Ferrocxanides.T The addltlon of potassium ferrocyanide to a uranyl salt solution causes the formation of a deep- red preclpltate or suspension, depending upon the concentratlon of uranium. The reaction 18 used much in qualitative anal- ysils for the identlfication of uranium. However, it 1s little used for quantitatiye separation. The separation 1s poor and there are many :I.n‘l:er-ii'el:'encses.-ai Separation can be made from beryllium in a weakly acldlc sulfate solution.22S Fluorides. ' Hydrogen fluorilde preclpitates uranium (IV) as the tetrafluoride. The preclpitate is gelatlnous and difflicult to filter.ifi Separation 1s made from metals com- plexed by fluoride ilons, eg., tantalum and zirconlum. Uran- 1um may be reduced to the (IV)-state with zinec in a solution made sllightiy acidic.}—9—6— 42 The double fluorldes, eg., NaUFS, are pparingly soluble even 1ln the presence of atrong acids.igé Separatlon can be made under these condltions from Mo, Ti, Ni, Co, Mn, Cu, Fe (1I), and Vv (III). Alumlnum preclpitates as the double salt, Na,AlF¢. Iron (IIT) precilpltates in part. Reductlon to uranlum (IV) may be done 1n the presence of fluorldes wlth tron (Ir).220:222 Rongalite (N H,S,0, * 2CH,0 - 4H,0) also hasa been used to effect-reduction.gig _ Hydroxides. The additiofi of a metal hydroxide to a seolution of uranyl ealts results 1n the formatlon of the metal uranate. It has commonly been assumed that the metal diurante, M2U207, 1s precipltated by ammonlum, sodium, or potasasium hydroxlde. However, experimentsl evlidence 1ndi- cates that the composltlon of the preclpltate depends upon the coridltlons which exist during precipltation and upon the subsequent treatment, such as washlng, whlch 1t re- ceives.23:7237 Armonlum hydroxideT preclpltates uranlum quantitatively atpH 4 or grea’cer.-a-lt The presence of ammonium salts and macerated fllter paper facllitate precipltation. Separation 1s mede from alkall meftale, alkallne eartha, and cations ' forming ammonla complexee. Repeated precipltations may be necessary to glve sufficlent separation. Phosphorus, vana- dium, ellicon, boron, alumlinum, lron and other elements of the ammonium hydroxide analytical group alsoc are precipitated.glg— Complexing agents: carbonate, oxalate, cltrate, tartrate, fluoride, etec., interfere. Preclpitation with alkall metal hydroxldes is slmllar to that with ammonlum hydroxlde. Uranlum may be preclpltated In the presence of carbonate wlth sodium or potasslum hydroxide of sufficlent concentratlon. Carbonate lon lnterference may be removed by heating. 43 Pale green gelatlinous UO2 . H20 18 precipltated from uranium (IV) solutions by ammonium and alkall metal hydroxides. Todates. Uranium (IV) 18 precipltated from an acid solutlon by potassium 1oda.te.gi Separatlion can be mede from copper, molybdenum, and reduced vanad.1.1.:.111.g-3-g Aluminum 1n amounts up to fifty times that of uranium does not 1lnterfere. Larger amounts of aluminum and divalent iron 1n any concen- tration cause lncomplete precipltation. Titanlum, zlrconlum, cerlum (IV), and thorium preclpitate with 1odate. 32 Mercuric oxide. Uranium 1 preclplitated when a suspension of mercurlc oxide is bolled 1n an aqueous solution contalning ammonium chlo::-ide.ii Separatlon 1s made from alkell metals and alkelline eartha. Hydroxy aclds 1nterfere. Peroxides.* Hydrogen peroxide preciplitates uranium peroxlde, U04 . xHEO, from sllghtly acldic solutions. The reaction occurs in the pH range 0.5-3.5. The optimum range 1s 2.0-2.5, Hydrogen lons released wlth the formatlon of uranium peroxlde are neutrallzed with ammonia or ammonium acetate. Complete preclpltation requires an excess of hydrogen peroxlide. Quantlitative separatlon may be effected by freezing the solutlon, allowling 1t to ptand, and filtering at 2°C. The separation from most elements 18 good slnce 1t 18 done from an acldilc aolution.ii&g}g Plutonium, thorium, hafnium, zlreconlum, and vanadlium also preclpltate. Iron dnterferes by catalytlecally decomposing hydrogen peroxide. Small quantities of 1ron may be complexed wlth acetlc, lactle, or malonle acid. Low ylelds may result from the use of malonic acld. Ammorium, pofasslum, and alkaline earths re- tard the rate of precipltation. Complexlhg lons such as oxalate, tartrate,lsulfate, and fluoride 1n large quantitles, also interfere. Fluorlde lon may be camplexed with aluml- num . 2328 44 19 Phosphates. Phoephorlc acld and sodlum monohydrogen phosphate,precipitate.anHPou from uranyl solutions. Uranyl ammonium phosphgte, UO,NH),POy, 1s precipitated by (1~11+14)2HP01l or NaeHPou in the presence of ammonlium acetate.* Preciplitation ‘is made in the pH range 1.2-2.3, 1.7 belng optimum. It ie not very eelectlive. Zirconlum, bilemith, and thorlium pre- cipltate under similar conditlons. Alksll metals are retalned. Separatlon 18 made from vanadlum. Both UOéHPOu and UOQNH4P04 are poluble in mineral acida.3E Phosphate precipitation of uranium (IV) 1s more selec- tlve. 1t 1s made from dllute hydrochlorlec or perchloric acld solutlons. Separatlion is made from manganese, lron, vanadlum and most other elements. Zlrconlum, thorium, and, to a emaller extent, titanium and tin precipitate.lgé:lg& Aluminum interferes by the formatlon of soluble complexes with uranium and phoaphate 1ons.22 With sulfate and aluminum present, uranium l1e precipltated in a narrow pH-range around one. At higher pH, the soluble aluminum-uranlium-phosphate complex 18 formed; at lower pH, the soluble uranium-sulfate complex. Chromlum in excees of 0.2 gram per 100 milliters ceueeg Incomplete precipita.t—ion.lgé Large amounts of fluorlde ion prevent precipitation.lgé Sodlum hexametephosphate [(NaP03)6] also precipltates uranium (IV) from acid solutiona.gfig Adherence to fsirly stringent condltlone allows for complete preciplitation., A 3N. B0, solution of uranium (IV) 1s heated to 60-70°C. If more than 2 mg. of uranium are to be precipita%ed, a freshly prepared 2% hexametaphosphate solution 1s added until its concentration in the precipltating medium 1s 0.30-0.35 per cent. To preclpltate smaller amounts of uranium, 'a 0.5 per cent solution of thorium chloride ls added as carrier and the hexametaphoephete added until it 1s in excess 25 per cent with respect to the thorium, 1.e., molar ratlo of Th:PO3 45 is 1:5. Coagulation 1s improved by heating in a water=-bath for ten to fifteen mlnutes after precipitatlion. Under these conditlons separation 1s made from V (1) and (IV), Fe, du, and other di- and tri-valent metals. Incomplete precipitation occurse wlth 1Increased or decreased acldlty -- probably because of enhanced solubllity of the compound and complex formation, respectively. Precipltation from sulfurlc acld 1s incomplete Pecause of urafiium-sulfate ¢omplex formation. Under certaln conditions both uranium (IV) and (VI) form complexes with hexametaphosphate. Hypophosphoric -acid (H4P206), eodlum dihydrogen hypo- 2P207) precipitate uranium (IV) from acld solutions.' Other phosphate (Na2H2P206), and sodium pyrophoaphate (Na tetrevalent metals, T1, Zr, and Th, also preclpltate. Separa- tion is made from uranium (VI) and trivalent metals-in-general.ifl Phosphites. Sodium hypophosphite (NaHePOE) and ammonium thiosulfate or sulfurous acld preclpitate uranium from a bolling, dilute acid solut-ion.gfll Zirconium and tltanium precipitate under similar condltlonse. These elemente may be separated prior to uranlum by bolling with sodium hypo- sulfite alone. Elements forming acld-~lnsoluble sulfides are removed wlth hydrogen sulfide before adding sodium hypo- ~phosphlte and ammonium thilosulfate. Sulfetes. Uranium (IV) sulfate 1s practically insoluble in 47 per cent perchlorilc acid. Precipltation is made 1n a sulfuric acid medium. Uranium is reduced on a mercury cathode and concentrated perchloric acid 18 then added. Sulfldes. Ammonlum sulfidef or polysulfide precipitates brown, amorphous uranyl sulfide. Numerous other elemente are preclpltated under similar cc::onclit:iona.?-ii Complexing agente such as carbonate, pyrophosphate, and citrate 1nterfere.3fi Uranium (IV) salts are precipiltated as U0, * H,0 by ammonium sulfide.222 46 Hydrogen sulfide bubbled through a nearly neutral solu- tion of uranyl salts contalning hexamethylene tetramine pre- cipltates uranium 1n a readily fllterable, crystelline form of "uranium red."’ Separation 1s made from alkall metals end alkallne ea.r-th-s.ifl--’-lgz Vanadates. Ammonlum metavanadate firecipitates ammonlum uranyl vanadate from uranyl soluftions buffered with ammonlum 'acetate.éfi- Uranovanadlc aclds are preclpitated at pH 2.2- 6.5.gflg Wlithin thepe limltas, the compoeltion doea not depend upon the hydrogen lon concentration. It does depend upon the vanadium : uranlum ratlo present'in solution. Compounds correspondlng to the formulae H[UOE(OH)2V03]-H20, H[UOQ(OH)(V03)2]'2H 0, and H[UOE(VO3)3]'4H20 2 have been-identified.gfig Ammonlum esalts of These aclde have been syntheslzed 1n the presence of ammonlium chloride.gflg Ammonilum uranyltrimetavanadete 18 the least soluble. However, itse formatlon 18 a long processa at room temperature. Heatlng greatly accelerates 1te rate of formatlon. Organlc preclpltants. Organlc preclpltating reagents are llisted alphabetically. 3-Acetyl-d-hydroxycoumarin (3-acetyl benzotetronic acild). An alcoholle solutlon of the reagent added to a uranyl salt solution forme & pPale yellow preclpitate insoluble 1n ethano%%i Precipitation occurs between pH 1.5 and 7. Below pH 1.5 the reagent precipitates. The thorium complex 1s soluble in alcohol, but precilpitates from an agqueous solution at pH 2-4. Lanthanum and cerium (III) do not interfere when present in amounts ten times that of uranium. Cerlum (IV) interferes even in small amounts. Acradine. Uranium (IV) and (VI) are preclpltated by the reagent With the addition of ammonium thiocyanate.gli Iron (III), cobalt, copper, zinc, cadmlum, mercury, and bils- mith precipltate.2it2216 47 Aldehyde ammonla precipltates an.glé Alizarin and Allzarin Red S (sodium alizarin sulfonaete). Uranium 1s preclplitated slowly by the reagents when the uranyl ion concentratlon 1s less than 20 mlicrograms per m111111ter.212 Aluminon (ammonium selt of aurintricarboxylilec acid). The reagent precipltates both uranium (IV) and (VI) from sulfate solutlone at pH 3_5_§l§ Amines. Ammine salts, generally of the form U02(Am1ne)2 X5, where X is an acld radical such as acetate, chlorilde, nitrate, etc. have been prepared from acetanilide, anti- pyrene, bromoantipyrine, dilethylaniline, exalgin, nitroso- antlipyrine, p-nitrosodimethylanilline, phenacetln, pyramidon, pyrldine, qulnaldine, and quinollne. Mono-, trl- and tetra- ammine Bglts also have been formed. The salts are generally prepared 1ln anhydrous chloroform or amyl alcohol solutiona. However, some of the more stable salts may be precipltated from agqueous or alcohollc solutions;glfligii_ 2-Amino pyridine precipltates UO3.glé Ammonilum benzoate. Uranyl lon 18 precipltated by the reagent from slightly acidic solutions heated to bolllng. A 0.05 N solution of the reagent contalning about 2.5% NHuOH 1s bolled separately and added 1ln an excess of three to four times the uranlum present. Carbonate lon prevents quantitative prfi_-c:fi.p:l;t-a.t:-il.c>n.-1-§2Lgflz Ammonium dithlocarbonate precipitates uranium (VI). Derivatives also are formed with Al, Mn(II), Fe(II), Co, Ni, Cu(II), Zn, Ag, Sn(IV), Pb, and p1,246 Anthragallol forma brown precipitates or solutions with o, vodt , Fe3t, cu?t, and Moofi' . 212 Anthranilic acid. Uranium (IV) is precipitated from a solution of the reagent buffered with ammonium acetate. The reagent added to a 0.1gL02(N03)2 solution forme a heavy 48 yellow preclpltate. The amount of preclpltate 1ls lncreased by the additlon of 1M acetlc aclid; decreased by the addltlon of 1M sodium acetate. Fifty micrograms of uranyl ion per drofi of solutlion glves no obaservable preclplitate. In acetilc acid-sodlum acetate buffered scolutlionas, slightly soluble Balts are formed with the reagent and Mn, Co, Ni, Cu, 2Zn, cd, Hg(II),and Pb.232 Areonlic acide. Benzenearsonic acidf preclpltates uranium (IV) in a weakly ecldic solution, pH 1-3. Titanlum and cerlum (IV) are partially precipitated. Thorium, zir- conlum, hafnlum, tin (IV), nlobilum, and tantalum are quantitatively precipitated.l” Arsonilic acid (p-aminobenzenesrsamic acid) precipitates uranium (VI) in 2 weakly acidic solution, pH 1-4 or great%%; At pH 2.1 or greater the preclpltetlon 1s quantlitatlive as evlidenced by negative ferrocyanlde teste of the flltrate. Other lons which precipitate from neutral or alightly acidlce 2+ 2+ 2+ 4+ ’ » solutions 1nclude Cu™ ', Zn Ca™', end U With the addition of sodlum acetate, aluminum and ferrlc lons also precipitate.glé Qther substituted arsonlic aclds which glve difficulty soluble uranyl salts are 3-nitro-4-hydroxybenzene- and methane-arsonlc acj.dsl.:j-E Bis-benzenephosphonlc acid. Tests on 50-150 mg/i uranium (VI) in sulfurlc acld solutions in the presence of approximately 100- to 1l000-fold excess ferrous, sulfate, aluminum, magnesilum, and phosphate lone gave nearly 99% preclpitation with the reagent. Optimum condltions for precipitation are pH 1 25°C, and 10/1 molar ratio of reagent to uranium.g&-El Benzenesulfinlc acld precipitates uranium (IV) in acldic solutions. Iron (III) and the tetravalent lons Ti, Sn, Ce, and Th &also precipit—a.te.gli 49 Benzopurpin precipitates uranium (IV) and (VI).glé. Bengoylacetone precipltates uranium (VI).glé 5=-Bromo-7-carboxy-8-hydroxyquinoline precipltates uranlum {VI), copper, zine, cadmium, mercury, and 1ead.gflg 5-Carboxy-8-hydroxyquiholine precipltates uranium (VTI) i1n solutions buffered with acetic acld and sodium acetate. Iron, copper, zlnc, cadmlum, mercury, and lead precipitate.gflg 7-Carboxy-B8-hydroxyqulnoline preclpltates urenium (VI) In ammonlacal tartrate aolutlons. Catechol forms compounds with tetravalent uranium, sillcon, titanlum, zirconium, and thorium.gli Catechol comblned wlth pyrldine preclpltates hexavalent uranium.gli— Cresotinlec .acld 1n the presence of sodlum acetate pre- eipltates uranium (IV) from solution. Aluminum end iron (III) also precipitate. Separetion 1s made from Cr, Fe(II), Co, N1, Cu, Zn, Cd, and Mo.2t3.210 Cupferron (ammonium nitrosophenylhydroxylamine).f Uranium (IV) 13 precipltated from acidic solutlons by the reagent. Good separation i1s made from other elements 1f this precipltation follows one in which uranium was kept 1n the hexavalent atate. Ions whlch are preclpitated by cupferron from acldiec solutione lneclude T1, V, Fe, Ga, Zr, Nb, Sn, Sb, Hf, and Ta. Ions which are not preclpltated under such conditions include the alkall metals, alkalline earths, Be, B a8 borate or fludborate, Al, P, Cr, Mn, Ni, Zn,and U(VI). Precipitation 1s usuelly made in a sulfuric acid medlum but hydrochloric or organic aclids may be used. Nltric acld should be avolded; also perchloric acld 1f the precipitate 1s to be 1lgnited. The presence of a reduclng agent, hydrcx- ylamine or sodlum hydrosulfite, facllitates complete pre- clpitation of uranium (IV). The cupférrate may be filteréd or extracted with an organlic solvent puch as chlorof'orm.-3-&--'-gfig . 50 Hexavalent uranium ls preciplteted by cupfefron from neutral solutiona.gég Dibenzoyl methane forme & yellow preclplitate with uranium (VI) flé 3,5-Dibromosallcylaldoxime precipitatea U(VI), Co, Ni, Hg(II), and Pb.22% 4,4'-D1hydroxy-3,5,3',5'-tetra(hydroxymethyi)'-diphenylmethane precipltates U(VI), Mn, Fe(III), Cu(II), and Hg(II).glg Dimethylammonium dimethyldlthiocarbomate forms & red precipitate with uranium (vI).2L8 Diphenyl thiocarbgzlde precipitates uranium (VI) from neutral solutions. Copper (II), silver, lead, and bilsmuth also preciplitate with the reagent.glé Dipropylamine forms a yellow preclpitate with ura.n:l.um.glé Digalicylalethylene dilmine precipltates uranium (IV) and (VI). Most heavy metals are precipltated by the 1:'ea.gen1;.3i 216 3. Ethylenedlamine and uranyl nitrate form an Ilnsoluble Ethanolemine precipitates UO double salt, U0,S0) (H,S0) ), NH,CH.CH, N, 1n-alcoholic-sulfuriec aclad Bolution.gég Double salts of the same type are formed wilth plperazine and dimethylpiperazine. Sieam‘aslen:?-23 observed that a solutlon of ethylénediamine added to & uranium solutilon £Zlves a bright yellow crystalline preclipitate that le soluble In excess reagent. Ethylenedlaemine tetracetic acid. Uranium 1s precipitated when a uranyl acetate solutlon 1s bolled wlth so0lid reagent.gfifl ‘ Gallic acid precipitates U(IV), U(VI), Fe(iII), Cu(II), and Zn.gié Gualacel. A brown preclpltate resulta from the reactlon of the potasslum salt of gualacol and uranyl acetate in an aqueous solution.gié Hexamethylene tetramine (urdtropine)* 18 o weaker base than ammonlum hydroxlde and does not absorb carbon dloxide. 51 This reduces the llkellhood of carbonate interference and of alkaline earth carbonate precipitation. Uranium l1s preclpl- tated when the reegent 1B .bolled 1n a uranyl solutlion that contalns ammonlum lion and no excess ao:::l.d.-3£ Ions that form stable complexes with uranium interfere. Separation can be made from alkeli metals, alkaline earths, Mn, Co, Ni, and Zn. Zr, M, Fe, Al, Ce(IV), Th, and some other elements preclpltate. A double salt, U0,S50,-H,S0)*(CH,)Ny, 1s formed with the reagent and an excess of sulfuriec acld and uranyl aalt.géé a-Hydroxyacetophenone forms a whlte precipitate with hexavalent uranium.g:—L-é 1-Hydroxyecridine (1l-acridol or benzoxine) precipitates uranium (VI) in neutral solutlons. Calcium precipitates from neutral solutions; Mg,Ca, and Ba from alkallne solutlions; Cr(III), Mn(II), Fe(II and III), Cu(II), Zn, Cd, Hg(I and II), Te(II), and Pb from eolutions contelning acetic acld and sodlum acetate. Al, Sn{II), and Bl do not p]:-ecipil.tate.giI 1l-Hydroxyanthraquindne forme elightly soluble complexes wlth uranyl, cobalt, cupric, nickel, maghesium, and man- ganeae ions.gli l-Hydroxy-3-methoxyxanthone may be used to separate uranium, thorium, cerlc salte and cerlte earths.gig The ceric salte and cerite earths are not precipltated by the reagent. Thorium 1s precipitated at pH 2.6-4.0. Uranium (uranyl ion) precipitates at higher pH. 8-Hydroxyquinaldine. Tetravalent uranium 1s preclipitated by the reagent wlth the addltlon of ammonlum acetate. The precipltatibn of hexavalent uranium is almost quantitative in the pH range T7-9 from carbonate-free ammonlum acetate '%buffer.gég Iron, cobalt, nlokel, copper, cadmlum, and chromlum are precipltated by the 1:'eahgen1:,.-g-lé 8-Hydroxyquilnollne (oxine).T Hexavalent uranlum is 52 preclpitated as 1102(09}161\10)2 . CQI-L_(NO from weekly ecldlic or basic solutions.fii Quantitative recovery has been reported over the pH range 4.1-13.5. A large number of other elements are preclpitated by oxlne including Mg, Al, Cr, Fe, Co, N1, Cu, Zn, Cd, Mo, B1, and Th.glfiigég:ggi Uranium can be pre- clpltated 1n the presence of small amounta of complexing agente: fluorlde, hydroxylamine, oxalate,lactate, end ter- t-ra.’c-e.;ii Separation from small amounts of phoephate also can be made at pH 10-12 using an excess of oxine. Ammonlum carbonate interferes. Tetravalent uranlum and oxlne form a8 brownish-yellow deposit.gli Isatin-B-oxime (fi—isatoxime).f Uranyl and mercurlc ione are precipitated by the reagent from weakly acldile solution. Precipltatlon 1s incomplete but can be made quantitatlive by 1ncreasing the pH wlth sodlum acetate. A number of other elements precipltate under these conditlions including Fe(II), Co, Ni, Ag, Hg(I), and Pb.gé£ Separation can be madé from Mn(II), Zn, and alkaline earth-ions.géé In alkali tartrate polutions, uranium can be separated from cobalt and nickel.géé Isojuglone. The sodlum salt of thls reagent and uranyl acetate form a carmine-red precipltate after washlng wilth ethancl. Iron, cobalt, nickel, zine, cadmlum, mercury, eand lead are precilpitated by the reagent.géz Isonitroso-N-phenyl-3-methylpyrazolone. Uranyl nltrate or acetate forms a reddish-orange preclpltate with a 1% solution of the reagent 1ln a 50% alcoholle solutlon. Precipltation is quantitative with the addition of sodlum acetate. Mercury (I) and (II), copper (I) and (II) and uranyl lons preclpitate in acidic medla (nitrate or sulfate). In acetate solutions, 'Ag, Cd, Ni, Co, Zn, Cu(II), and U022+ lons precipltate. By reducing the acidlty wilth sodlium acetate, salts of Ag, Pb, Bi, Cd, Mn, N1, Co, Fe(II), and Fe(III) can be precipitated from 53 nitrate solutlona. Salts of T1(I), Sb(III), Sn(II), A1, Cr(III), and the elkaline earths do not precipitate.28 Lguramidine hydrochlorlide. This reagent has been tested for the separatlon of uranium from phosphate solutionsfggg At pH 2.45, 75% of the uranlum was preclpltated. N-Lauryl-lauramidine. Thls reagent also has been tested for the separatlon of uranium from phosphate sclutlona. At pH 2.45, 85% of the uranium was preclipltated. Meroapto-acetic acld forms a greenish-white precipltate wlth tetravalent uran:l.u.m.-gzl'-é-!--‘?-!'-é Methylamine precipltatee uranium (VI).E;E Methyl red causes uranium (VI) and aluminum to pre- cipitate.gli Morpholine precipitates uranium (IV) and (VI) as well as a number of other metal ions.glé A 1l mg per ml solution of uranyl nitrate shows only a yellow color with the reagent. No precipltate 1s formed.glé p~-Naphthoguinollne 1n the presence of thlocyanate 1ion precipltates uranium (VI), mercury, bismuth, copper, cadmium, nickel, cobalt, zine, and iron (III) from sulfuric or nitric acld faolut:l.ons.‘?’—z-§2 Neo-cupferron (ammonium a-nitrosonaphthyl hydroxylamine) 18 gimllar to cupferron 1n 1ts application. Uranlum (IV) is preclpltated by the J:'eagen‘r:,.g-:!‘--l£ | Nitrilotriacetic acld forms derivatives with uranium (VI), iron (III), nickel, and copper (II).EIQ m-Nitrobenzolc acld precipltates uranium (IV).QE o~Nitrosohydroxylamlnophenyl p-toluenesulfonate forma a yellow precipifiate wlth hexavalent uranium. Many other me- tallic 1ons are preclplftated by the reagent including Al{ Cr, Fe(III), Co, Ni, Cu(TI), cd, Ia, Ce, Hg(II), Bi, Pb, and Th.2L: a-N1ltroso-f-naphthol 1 deposits uranium (VI) as & very fine, yellow-orangeii to b]:'curm-?:li precipltate. Precipitation 54 1s made in the pH range 4_0_9_4,212 Metals such as 1iron, cobalt, nickel, and.copper are precipitfated from elightly acid solutions. Molybdenum as molybdate ion, zine, and uranium (IV) form colored Boll'rb-ions.gli Aluminum, chromlum, and cadmium give no visible reaction.gli The uranlum compound can be extracted wlth amyl alcohol.§£ B-Nitroso-a-naphthol preclpitates uranyl ion from slightly acidle solution. Iron, cobalt, nickel, copper, zine, and molybdate lons also are preclpltated by the reagent. Alumi-~ num, chromium, cadmium, and uranium (IV) give no vislble reactlons. The precipitation of uranium (VI) 1s most nearly complete 1n an acetate buffered solution.gli Oleic acid 18 a precipltant of uranium (VI). 216 Oxalic acid' precipltates uranium (IV) from aéidic solution.éi Strongly complexing organlc compounds and fluoride, sulfafe, and large amounts of phopphate 1lons inter- fere. Uranlum 1s preclpltated from 2-3N hydrochlorlic acld media. At lower aclditles other metal oxalates preclpltate, eg., Fe(II), Zn, Cu. At higher acidities the solubllity of uranium (IV) oxalate lncreases. Immediate filtration of the preclipltate may result 1n losses up to 1% of the uranium to the filltrate. _Recovery of uranium may be made more quantl- tatlve by chllling the solutlon and allowlng it to steand. Small amounts of menganese, 1ron, and nlckel may be carriled wlth the preclpitate. Nlobium, the rare earths, and thorium precipitate under eimilar conditions. If uranium 1la reduced on a mercury cathode prior to preclpltatlon, no cations in moderate amounts interfere except rare earths and thorium. Precipltation of uranium can be made 1n cold 1N nitric acld solutions.gég The uranium content should belless than 70 grams per liter. Enough oxallc acld 1s added to glve a 10% exceas of the smount theoretically required to precipitate U(cgou)e. The uranium then 1s reduced to the (IV)-state by 55 5 adding sufficlent rongalite (Na2H 04-20H20'4H20) to glve a 255 7-10% excess of 1 mole of rongalite per mole of uranium. Phenanthrene quinone monoxime preciplitates uranlum (1Iv) and (VI), aluminum, iron, cobalt, nickel,copper, &and zinc.glé Phenoxarslnlc acld preclpltates hexavalent ura.nium.gflg 2+ Phthlocol precipltates U4+, Udg+ s 4N ions.glé , and Mo0§~ Picrolonlc acid precipltates tetra- and hexa-valent uranium and most other metallic 1on-s.gli Piperazine. (See ethylenediamine). gzridinef does nof absorb carbon dloxide like ammonium hydroiide does. Thle reduces the-possibility of carbonate interference or of alkaline earth precipitation 1n a uranium separation. Ammonium nitrate facilitates uranlum precipltation, Sulfate lon hinders 1t. Separation can be made from elkall metals, alkaline eartha, Mn, Co, Ni, Cu,and Zn. 2Zr, Ti, Fe, Cr, Al,and othérs are preclpltated by the reagent.gfl Pyrogallol and pyridine comblne to form & derivative with hexavalent uranium.gl& Quinaldlce acidT forme & yellow, amorphous preclpltate wilth uranyl ion.glé Preclpltation 48 made from a neutral or weakly acidic (pH 2-3) solution 1n the presence of ammonium chloride. The reagept preclpltates a number of metals Including copper, 2zlne, cadmiumgzi and uranlum (I\J").—E-!'-2 Uranyl ion 18 not precipitated in the presence of alkall tartrategZE or & high concentratlion of acetate 1on.'glz Quinizarin (1,4-dihydroxy-anthraquinone) precipitates uranium (IV) and (VI), iron and copper.glé— Rhodizonle acld forme a blue-black preclpltate wlth tetravalent uranium. In neutral solutions, Ag, Hg(I and II), T1, Pb, Cu(II), Cd, Bi, Zn, Sr, Ba, Fe(II), and UO,(II) lona are precipitated. At pH 2.8, Ag, Hg(I), Ti, Pb, Cd, Ba, and Su(II) are precipitated.gzi 56 Salicyellic acld. The sodium salt of the reagent forms a greenlsh-whilte preclpitate with uranium (IV). Under con- aitions tested, Al, Cr, Fe, Co, Ni, Zn, Cd, Moch , and UG lons were not precipitated.gli Sebaale acid precipitates uranium (IV).fiE Sodlum- acetate preclipltates sodium uranyl acetate from fieubral or weekly acldic solutions of uranyl salta.lgg The - method l1s not very useful for the precipitatioh of traces of uranlum. The solubllity of sodlum uranyl acetate in a solutlon 5M 1n sodlum nitrate, 1M in acetic acid, and 0.5M In sodium acetate 1s about 100 mg per liter.gzg Neptunlum (VI) and plutonium (VI) also precipitate under these condi- tions. The additlion of sodlum acetate and zlnc acetate to a neutral or weakly acldlc uranyl salt solution preciplitates the triple salt, sodium zinec uranyl aceta.te.122 Sodium diethyldithiocarbamate preclpltates tetravalent uranium, aluminum, iron, cobalt, nickel, copper, and cadmium.gli Hexavalent uranium may be preéipitated when both uranyl and reagent concentrations are suffilclently large.giéigzz Scdlum ethyl xanthate forme an orange precipltate wilth uranium (VI).glé Strychnine 1n the presence of fluoride lon precipiltates hexavalent uranium as 7(C,;H,,0,N,HF) * 6(UO2F2) " 2HF. The solubllity of the preclpltaete. in water at 25°C 1s 47.5 mg/100 ml; in 60% alcohollc solution at 25°C, 30 mg/100 ml.2(8 Tannic acid (digallic acid)f and tannin (a glucose ester of tanniec acid)* react with uranium (VI) to glve a deep-brown .precipit-ad;e.3-E Elements arranged according to decreasing ease of precipltatlion by tannin are Te, Ti, Nb, V, Fe, Zr, Hf, Th, U, Al.’gzg The posltlion of chromlum 1n this series 1s uncertaln. Tantalum, titanlum, and nloblum may be separated by tannin in‘a slightly acidic oxalate solution. Uranium and others are preclpitated by adding more tannln and by makilng 57 "the solutilon ammoniacal.. Uranium mey be preclpltated from such solutions in the presence of mrbonate, acetate, or tartrate 1on£t.-g92 Thioslnamine. Uranium and cadmium are preclpltated when ‘an alkaline solution containing these elements 1s bolled with the reagent.-a-gg Carriera. Trace amounts of uranlium may be removed from solutlon by the use of gatherlng agents or carrlers. The cholce of a particular agent depends upon the conditions under which precipltation 18 to be made and upon subsequent chemiatry to which the precipltate is8 to be subJected. Rodden and Warfifi have deseribed the applicatlon of several carrlers: ferric, aluminum, and calclum hydroxide. The use of barium carbonate and thorium hexametaphosphate has been mentioned in the Bec¢tlon on lnorganlc precipltanta. Mag- negium oxlde and thorium peroxlde have been used.ifi The oxlde and salts of antimony,ggliggg calcium fluo:r:*icie,ill and the phoephates of zirconium,lgz bismuth,ggi and thoriumlgz’ 240 have been used to carry uranium from reduced solutions. Uranium (IV), in general, should behave simllarly as nep- tunium (IV) and plutonium (IV). These are carried by lanthanum fluoride, cerlc and zlrconlum lodates, cerlic and thorium oxalates, barium sulfate, zlrconlum phosphate, and bismith a!raonate.gzé Uranlum (VI) does not carry wlth these agents provliding the concentration of either carrier or uranlum 13 not too large. Complexes. The preclipltation of uranium in normally precipltating medla is inhibited by the formation of sBoluble complexea.ii Carbonate ion 1e a very efficlent complexing agent of uranyl ion. In ammonium hydroxlde solution, uranium can be Beparated from iron,_titanium, zirconilum, and alumlnum with carbonate lon present. In ammonium sulfide solutlions, carbonate lon makes possible the separation 58 of uranium from manganese, lron, cobalt, zlnc, and titanium. Ammonium carbonate prevents the preclpltatlion of uranium with phosphate. Preclpltatlion with sodilum carbonate makes posaible. the separation of uranlium from berylllium, menganese, lron, cobalt, nickel, zine, tltanlum; zlrconium, and the alkallne earths. SodIum peroxide faclllitates the separation of uranium and other metals with sodium carbonate. The addltlon of the per- oxide alone to acld solutlions of 1iron, cobalt, rare earths, titanium, zlrconium, hafnium, and thorium causes thelr precil- pitation while uranium, 1f present, remalns 1n solution. Uranium dces not preclipltate with tannlec acld 1n gelightly acldic solution wlth oxalate lon present. Titanlum, nloblum, tin, tantalum, and tungeten .are preclpitated under such con- ditlons. Oxsalate lon also ilnterferes 1ln the precipitation of uranium by ammonla. | Tartrate, cltrate, and melate lons prevent the precipl- tatlon of uranium by ammonium hydroxlde or suli‘:l.dea.i-li Sallcylic acid and hydroxylamlne have both been used to complex uranium in separations from rare earth elements.fii Hydroxylamlne has been used In separations between uranium and beryllium, aluminum, Ilron, and ’cnor-:I.ul:n..-3--i Complexing agents that form weak complexes with uranium and relatively strong complexes wlth other metallle lons meke geparatlon posslble between the two: uranlum lg preclpltated by a sultable reagent; the other lons remaln in solutilon. Ethylenediaminetetrapetic acld (complexone II) and 1ts disodium salt (complexone III) hafie been used successfully in this respect. TUranlum has been preclpltated with emmonla in the presence of complexonea wlthout interference from Al, Cr, Mn, Fe, Co, N1, Cu, 2n, C4, La, Ce, Hg, Pb, Bi, ' ahd the alkallne ean:-ths.g§£ The recovery of uranium l1s not entirely quantitative slnce the complexling agent 1lncresaaes the solubllity of the ammonlum uranate.196 28 The abesorp- 59 tion of lmpurlities 1n the precipltate may necessltate dissclution and repreclplitation of the uranium3l2§ Berylil and titanlum follow the uranium chemistry;ggg | - Quantitative recovery of uranium from the aforementloned cations: Al, Cr, Mn, Fe, etc., can be made with ammonium monohydrogen phosphate, (NHA)QHPOM’ in the presence of ethyle nedlaminetetracetic acid.ggé&ggz Beryllium and titanium agaln interfere. Small amounts of tltanlum may be complexed wlith hydrogen peroxide before the addition of other rea.gents.ggz _ Sen Serma and Ma1111288 have studied the separation of uranium from other elements using 8-hydroxyquinoline (oxine) as preclpltant and complexone III as complexlng or masklng agent. It was found that complexone had no maskling actlion on uranium in the pH range 5-9. In a solution buffered with acetle dacld and ammonlium acetate et pH ~5.3 quantitative separation was reported between uranium and Al, Mn, Fe(III), Co, Ni, Cu, 2n, Zr, Cd, rare earths, Pb, Bi, Th, and P205. In ammoniscal medium at pH ~8.4, & sinllar separation was made from Vé05, M003, and W03: Steele and Taverner,lgg however, were unable to duplicate the above results. Solvent extraction. The solubllity of uranyl nitrate in organlic solvents has long been recognized.lgé The ability of dlethyl ether to extract thils salt has been used 1in gystems of anelysis for many years. However, 1t 1s only within recent yeare (starting in the 1940's) that widespread use has been made of solvent techniques as a means of geparating and purlfylng lnorganlc substances in general 289-299 and uranium in particular.191’192’194’197'192’3903305 The conditions under which uranium may be extracted are many and varled. In the present paper, extraction from aqueocus solutlon 1a consldered. However, extractlion from 8olid phasesigi::gz and slurriesigi has been lnvestigated 60 and a favorable uranium partition has been found. Conditlons whlch affect the extraction of uranium from aqueous solutilon by organic solvent are the composltion of the aqueous phase, the nature of the organlc phase, the temperature, and the time of equillbration. In the aqueous phase, such factors ag uranium, acld, cocmmon anlon, forelgn anlon, and forelign catlon concentratlon must be considered. The nature of the organic phase depends upon the type and concentratlon of solvent and dlluent. If the organlec phase 1s not initlally barren, lts concentration of uranium, acld, ete., affects partition. Becauge of the number of varlables and the large number of uranlum solvents, one cannot conslder, in a volume of thils glze, each Bolvent 1n the l1light of each varlable. Indeed, the behavlioral relatlon between solvent and the afore-men- tloned varlables 18 known for only a few well-studled solvents. The purpose of the present paper 1B to provide information on the condltions best-sulted for the quantitatifie extraction of uranium or for the separation of uranium from interfering elements. Thls 18 done as much as possible in graphle or tabular form. The solvente are dlvlided l1lnto flve general classlfications: 1) ethers, esters, ketonea, and alcohols; 2) organo-phosphorous compounds; 3) amlnes and quaternary ammonium selts; 4) carboxylic aclds; 5) chelating agents. Dialkylphosphoric aclds, eg., dibutyl phosphate, are classified as organophosphorusa com- pounds rather than chelatling agents. Carboxylic aclde are classifled g8 such,although gome may aleo be conslidered chelating agente, eg., sallcyllc acid. A number of extrac- tants may serve also as dlluents or secondary solvents for other extractants. Such systems are descrlbed under the primary extractant. For example, a cupferron-hexone system is described under "cupferron" rather than under "hexone! 61 In the discusslon, the terms "extractant" and "solvent" are often used Interchangeably. "Diluent" 1s used to describe a secondary solvent rather than the term "inert solvent." The cholce of dlluent may appreclably affect the partition of uranlum. A number of terms that are frequently used are defined below. Partltion or -extractlon coefflclent: a = o2 = concentration of a substance i1n the organic phase T, ~ concentration of the same substance in the agueous phase Percentage extracted: a P = Tha X 100, when equal volumes of both phases are present after shaklng. Mass ratlo: - Mo _ amount of a substance in the organic phase _ . Yo K fi; ~ amount of the same subsftance 1n the aqueous V; phabse Separation factor: concentratlion of substance A in the organlc¢ phase concentration of substance B iIn the organlc phese B = concentration of subgtance A in the aqueous phase concentratlon of' substarice B 1n the aqueous phase Equilibrlum laws. The physlcal chemlcal principles Involved in the solvent extraction of uranyl nitrate have o [+ been summarized in references 308-312. Detalled methods of treating the varlous equlllbria involved have been dev:{_:aed.l;l?‘-fil;’:—:ili A more slimple approach,adapted from a paper by Carleson;;l 18 herewlth presented. It may be assumed that within a certaln concentration range an average uranlum complex 18 extracted. The complex is represenftative of a whole set of complexes and may be written H{M("'x)L(x_'_y)(HzO)h - (8),- M®. in this case, may be Ut or UOEE. L, as written, ig a slngly, negatlvely charged ligand. It may be more highly charged. & represents a solvent molecule. The subacripts y, h, and n need not be Integers. The reactlion for the extraction mechanism may be wrltten ! 62 M¥aq + yiTaq + (x+y)L7aq + nS org = HyML(x+y)Sn(H20)h°rg + mH,,0. The thermodynamic equllibrium constant for the reactlon is m ‘ [HyML(x+y)Sn(H20)hJ org {H26Y > [t 1Y) [818ng - £(7) where {i}-and [ 1, respectively, represent the actlvity and concentration of a quantlty in the agqueous phase unless otherwise identified by the symbol "org.fi f(7) represents the product of the actlvlty coeffleienta. The partitlion coefficlent is approxlmeted by [HyML(K+Il$n(H20)h]org .o [ ¥] The relaticn between the partlitilon coefficlent and equilibrium constant 1s log a == y loglHTlag + (x+y)loglL”Jag + n logl[Slorg -m 1og {§2§} + log f(vy) + log K. Information concernlng the extracted specles may be obtalned by measurling the partition coeffilclent whille varying the concentration of only one of the quantitles. A knowledge of the activity coefficients islthen requlred or the product of the activity coefficlents 1n both phases muet be kept constant. As gtated previously, the above approach to solvent extraction is a simplified verslon. It represents only an average extracted species. Among other things, 1t does not conslder the effect of water activity 1In tfie organlc phase, Bolvent activity in the aqueous phase, complex formatlion be- tween the varlous components 1in elther phase, or the formatilon of polynuclear species. These effects may be large or small depending upon the solvent, aqueous medlium, and uranium con- centration inveolved. ETHERS, ESTERS, KETONES, AND ATCOHOILS. Uranyl nltrate 18 extracted by many polar solvents whlich contalin donor oxygen atoms such as ethers, esters, ketones, and alcohols.ilg:igg— A 63 Extractlon from water solutlons 1s small unless the uranium concentration 1a appreclable. This 18 shown in figures 1-5 in which the data of McKay and co-workers,lzéilgz Wla.l:-ner-,-a-gl--f-igg and Vesely, et 81323 are plotted. In general, it has been observed-igl that: | 1) the extraction coefficlent of uranium decreases when the number of carbon atoms 1ncreases for a glven homologous peries of organlc solvents, ' 2) for a molecule with a given number of carbon atoms and a glyen chemical functional group, solvents wlth strailght chalns are more efflclent extractants than those wlth branched chains, 3) one or more double bonds in a molecule increases the efficlency, 4) primary alcohols are more efficlent than secondary ones, ' 5) the coefficlent of extractlon increases with the solubllity; but there 1s no well-defined relatlon between the two. | | Evldence consldered 1iIn the sectlon on non-aqueous sol- utlone indicates that uranium 1s extracted from agqueous nltrate solutions ae hydrated, solvated uranyl nitrate, UOE(Noa)E(H2O)hSh' Under approprilate conditions, the hydrated, sgolvated trinitrate-uranyl complex may be extracted. The relatlonship between partitlion coefficlent and equllibrlum constant for the extraction mechanism shows the extraction of the former species to be favored by ~ large free nitrate and free solvent concentrations and b& small water actlvity. Effect of nltric acld. The addition of nitric acld to the aqueous phase favors the extraction of uranlum by pre- venting or decreasing the hydrolysls of uranyl 1lon and by increasing the nltrate lon concentration.ig& Nitric acid 1s extracted also by the organic solvents. This requilres 64 59 URANYL MOLALITY (organic phase) T ! 1 ! 0.5 | _=0 - . “’ . - 'a‘ a 7 1 I | mg 0.4 ’p = L - D g I " i < o & o o 4 Z s 50 d 28 ¢ ;g o.2r = ™ 5| Joz 6 g O — q O . - ©

o 0.2~ ~- >« 2o = o S © oa — L = o = a‘-‘ $° ol e o 0 0.l 0.2 0.3 0.4 0.5 0.6 GRAM OF URANYL NITRATE per GRAM OF AQUEOUS PHASE Flgure 3-B. Partitlion of uranyl nltrate between water and nitro- methane and saturated ammonium nitrate (dashed curve) and nitro- methane. After R. K. Warner, reference 322. Temperature, 20°C. 89 4 | T T — 0.5 - o ~ % a W i © T e ‘2 0.4 - s &T o |: Q. S Zo _ z 0.3 ~ > - Sd - 290 = Sc _ I x O | - Sw 0.2 O o w E C)E = a & 0.l J ] @ q O @ 4 S A5 ] iy 0 v ‘.—‘J‘ Prre H-nfYS o 0.l 0.2 03 - 0.4 0.8 0.6 0 | 2 3 4 GRAM OF URANYL NITRATE per URANYL MOLALITY (aqueous phase) GRAM OF AQUEOUS PHASE () ®) Figure 4. Partitilon of uranyl riltrate between water and ketones. O, methyl ethyl ketone. @, methyl 1sobutyl ketone. A, methyl n-amyl ketone. A, dl-lsobutyl ketone. 0O, cyclohexanone, MHC, methyl cyclohexanone. h-A. After E. Glueckauf, H. McKay, and A, Mathieson, reference 185, Temperature, 25°C. 4-B, MHC curves, after V. Vesely, H. Beranovd, J. Maly, reference 323. Dashed curve--aqueous solution, 6M NH 4NO3. Remaining curves, after R. K. Warner, reference 321. Temperature, 20°C. Dashed curve--aqueous soclutlon, saturated ammonium nitrate. s 3 =T T 1 &® Q gL o (4] .g | E T fl > = = < 4 | F = O = - | 3 > P P > o | 2 3 4 URANYL MOLALITY (aoqueous phase) (a) T T I ! T a, 04} ' . o o & o i |: o 0.3 I 600) (~8->200) (25-100) (50) T.°C 25-6 2Uh-6 25-29 27-28 28-31 29 Vo/ Ve H o R B R The urenlum concentrations 1n paréntheses have been estimated by roughly adding the equilibrium uranilum concentratione of both esquecus and solvent phase. 81 T I o 1 | I | [ | ) B Fatili) | 10 g snLi _ - g ] C B Ca . i i = Y No S - 7 NHeg ] b N — > 1.0 E 3 L E : 0 E ] w i 4 ui : : o O 0.1 3 Z R o 3 = - — > _ < a 0.0l 3 0.00! L1y ) O ! 2 3 4 535 6 7T 8 9 10 i GRAM EQUIVALENTS OF NITRATE per iI000 g OF IN!TIAL AQUEOUS SOLUTION Figure 10, Effect of varlious nltrates upon the partition coefficlent of uranium wlth dlethyl ether. After V, Vdovenko and T. V. Kovaleva, reference 328. Conditions: 1 g. U02(N03)2 1n 100 g. of initlal aqueous solutlons; Temperature, 25°C; and Vo/Va = 1. 82 observed that the saltlng action of a mlxture of nltrates could be reasonably predlicted by the followlng method: The logarithm of a_ for each salt at a glven total nitrate molarity 1% divided by the total nltrate molarity. These indlvidual quotlents are then mul- tiplied by the nltrate molarity of the respectilve Balts. The sum of the resultling products 1s then equal to the logarlthm of the predicted partition coefficlent. . Hellman and Wolffiafi have studled the saltling action of varlous nitrates 1n the presence of nitrlc acld and thorium nitrate. Some of thelr results are listed 1n Table IX. From the data 1t may be observed that (1) thorium nitrate 18 generally & less effectlve saltlng-out agent on a normality basis than other metal nitrates and (2) the extractlon of uranlum becomes less efflclent as the amount of extracted thorium becomes appreclable. The effect of several forelgn anlons on the extraction of uranyl nitrate by dlethyl ether 1s glven 1n figure 11331 and Table X.igé Arsenate, molyhbdate, and vandate lons alao interfere with the extractlon of uranlum. The effect of these ione may be offset by the addition of ferrlc n;trate to the solution.33§ The partitlon of a large number of elements between various aqueous nitrate systems and dlethyl ether 1a8 given in Table XI and illuetrated 1n filgures 12-14. The lncreased dlstribution of heavy elements and fiesion product elements wilth increased niltric acld concentratlion should be noted. For a selective uranium extraction the nitrlc acld concentration should be minimal. H;srdeg--32 has recommended an aqueous phase 0.5-1M 1n nltric acld and 2.5M 1n magneslum nitrate for the quantitative extraction of uranium by diethyl ether. Mbre gelective extractlion of uranyl nitrate may be made from a saturated ammonium nitrate-solution, 0.05-0.1M in nitrlec acld. The extractlon can be made quanhtitatlive by repeated contacts with ether. 83 (Text continues on page 92.) Table IX. Distribution of Uranlum and Thorlum between Dlethyl Ether and Aquecus Solutione Containing Verlous Amounts of Metal N:I.trntan? Salting Total nitrate Composition of inltial aguascua Iuolution agent normality 0.5N HNO; + salting agent 0.5N HKO, + 1K T™(R0,), + aplting agent U extracted, ¥ U_axtracted, ¥ Th extraected, & . HNO, 3 23 10 0.1 5 52 ko 3.3 7 62 RG 21 T T LiN0, 2 10 22 0 3.5 36 5 31 5.5 T4 25 2 7 66 19 7.5 81 53 NH, KO 3 8 0.0 43 5 30 0.1 5.5 25 7 AT 0.5 9 57 0.8 10 59 12 59 1.2 Ca(fl03)2 2,37 13 2.75 11 0.0 3.62 32 .0 25 4.87 63 5.25 59 0.1 7.50 99 96 1.2 Mg(No,} 1.50 3 372 2.17 . 9 0.0 2,58 18 3.15 5 e o - by 0.00 5.5 29 9 0.31 Mn(No.) 2.5 18 - : 372 3.5 5.0 75 2l.0 0.0 6.0 5.5 7.0 65 T.5 87 8.5 70 8.5 T2 43 Cu(No, ), a.5 12 3 g.g 6 12 0.0 g_g o 50 0.5 10.5 87 62 15 11.0 18 52 La(RO.) 2.5 14 -5 6.0 93 18 0.2 6.5 39 2.1 M(N03)3 g:g 18 3 h;o 54 0.0 5.5 €3 2.8 6.0 96 T5 57 17.6 '1'11(1«03)1L 3.0 8 0.0 5.0 32 0.1% 9.0 58 8.0 11.0 52 11.% & Atter N. N. Hillman end M. J. Wolf, refersnce 336. Five ml of ether were shaken 10 mirutes with 5 ml of the agueocus phase of appropriate composition. 5,000 to 8,000 o/m of U233 tracer (52% counting yleld) wers supplied to the aquemu’phaue. Variation of the trecer from 100 to 100,000 o/- in 5 ml did not change the extracted. 100 1 ) — I a wJ . b kS \ _ —J é Ci — CeO4" g » _ (a3 § . - = F- ] 2z - g o D il o s0§" 2 o - = - W 0 —— o L . 2 POJ" 10 )| : 1 1 0 0.5 t.0 1.5 2.0 MOLARITY OF INTERFERING ION Figure 11. The effect of various anions on the extraction of uranyl nitrate by diethyl ether. After T. R. Scott, reference 337. Conditions: Aqueous phase - varylng amount of anlon, 3N HNO3, 1M Fe(NO3) ; aqueous phage and organic phase shaken 1 minufe at room tempera ure 85 Teble X. The Effects of Variocus Acids and Anions upon the Vistribution Coefficlent of Acid or ealt Urenyl Nitrate to Diethyl Ether.2 Compoalition of agquecus phase resent . P 4.23M c.-;n(uoa)2 4H,0 8M N‘HuNO? 6.86M NH, N0, (1000 g/1) (640 g/1 (549 g/1) None 19.95 0.645 0.364 HC1l, 1N 10.24 0.336 HC1, 2N 6.34 0.182 HNO5, 1N 43.56 1.162 HNOg, 2N 71.2 1.95 CH3COH, 1N 15.7 0.662, 0.616 CH4COH, 2N 10.52 0.720, 0.762 H,S0,, 0.0039% 0.613 H,S0y, 1N 29.6 0.024 H,50),, 2N 23.5 0.019 H,POy, 0.0058N 0.609 HyPOy, 1N 0.01 0.01 HyPOy, 2N 0.01 0.01 H,PC), 1N 37k 0= 3.98 0.067 HNOg, 2N _ (NH,‘L)Ecao4 * Hy0, 0.7 /100 ml 0.0847 HyC,0) - 2H,0, 0.7 /100 ml 0.0800 2 After Furman, Mundy and Morrison, reference 326. The 1nitlal volumes of ether and Aqueous Bolutlon were equal. Room temperature, 86 100 | { | ol LI LA * Ge(lV) 3 - i Z - w o Th(1V) J_ w 3 b - ISI 4 S ] > 4 o 3 3 = C 3 o C ] g - - a 5 4 F - 0.0! - - 3 : ] - 4 0.00I | ] | ] ] 1 1 L1 1 | I 0 |1 2 3 4 5 6 T 8 9 101 12 13 INITIAL AQUEOUS NITRIC AGID GONGENTRATION, M Figure 12. The extractlon of varlocus metal nltrates by diethyl ether. After R. Bock and E. Bock, reference 333. Condltlons: equal phase volumes. Metal nitrate Initlal aqueous Temperature concentration Th 0.1M 20 + 1°C Saturated LiNO3, Ca(N03)2, or Zn(NOg)Q solutions Ce(IV) 1M + 1°c Au(ITI O 1M room Sc(III 0.1 20°0C Saturated LANO3 solutilon a7 Table XI. Distribution Goefficlenta of Elementa batwesn Diethyl Ethar and Variocue Nitrate Solutlons. Hament H 0% o.gmmot o0.8MmoS umwo 2 1m0 N0 ewmmo.2 1.immo.d 1.3mmNo S 10MNH, NO 4.a_qca(m3)2 watdNE NO; 8atdLiNO, BHNH, NO, 611.4\1(:103)3 Al €0,001 ¢0.001 €0.001 0.0006 €0.0001 Am(VI) 0.6%2 5b{¥) <0.01 As 0.0015"0. 007" 0.o%8" 0.168 Ba €©-0005 «0.0005 <0.0005 <€0.0001 Be 0.01k 0.002 Bi 0.0001 0.0003 0.007 . 0.073 0.00031 ©0.021 B o.01" 0.033-0.39 cd <0. 00001 «0.00001 0.00001 0.003 <0.0001 0.0002 Ca 0.0003 0.0005 0.0005 <0 .0001 Ce(TIT) . <0.0009 Ce(IV) 27 0.095 0.714 30.3(29.3) Cr(III) «©.0001 <0.0001 and different initial acliditles. After V, Vdovenko, reference 343. Conditions: Aqueous solutlon--required amounts of niltrle acld and radloactlve material added to 3.5M solutlon of Ca(NO3)p; Vo/Va, 1. 91 Aqueous_thiocyanate systems. Uranium may be extracted from aqueous thiocyanate solutiona by diethyl ether.ifigii&l Table XII listse the fi&rtition coefficients of several elements from aqueous soclutlons of various thlocyanate con- centretiore fi A number of substances not -11sted in the table glve negligible distributions or dlstributions of only & few percent under the conditions tested: NH), , Sb(III), As(TII), As(V), Bl, Cd, Cu(I), Cr(III), Ge(IV), Ii, Hg(II), Teble XII. - Partition Coefficlents of Varlous Elements between Dlethyl Ether and Aqueous Thlocyanate Solutions.2 Composltion of the inltlal aqueous solutlon HC1 ot' ' NH4 SCN concentration M c M 3M oM ™ 0.1M a1l 0.5 20 0.011 0.099 0.275% 0.2M BeCl, 0.5 RT 0.039 0.987 5.29 11.9 | 0.1M CoCl, 0.5 RT 0.037 1.39 2.98 3.04 0.1M Gall, 0.5 RT 1.89 9.56 152 HC1 0.5 20 2.67 12.7 31.1 59.4 0.1M InCl, 0.5 RT 1.06 3.05 2.15 0.908 0.1M FeCl, 0.5 RT 8.00 5.13 3.08 1.14 0.1M MoOCl, ~0.5 RT 140 34.9 36. 42 0.1M ScClg 0.5 RT 0.145 3.95 8,06 0.1M(NHy)oSnClg 0.5 RT 144 950 > 1000 > 1000 0.1M T1Cl, 0.5 RT 1.43 5.25 3.94 3.22 0.1M TiCl, 0.5 RT ~0.15 0.1M U0,CL, 0.5 RT 0.821 0.117 0.160 0.072 0.1M VOC1, 0.5 RT 0.176 0.095 0.022 0.1M 2nCl, 0.5 RT 23.7 37.8 18.3 12.9 2 After R. Bock, reference 341. L as a101,7 £ 6.2M 4 6.6 Equal phase volumes equllibrated at room temperature. 92 N1, PA(II). Figure 15 represents the change in a, with thlocyanate concentration for aqueous solutions of different aciditiieei:E Anglysils of the ammonlum, uranium, thiocyanate concentration of the ether phase indicates that uranium 1s extracted as U02.(SCN)2:3El by dilethyl ether from aqueocus fluoride solutiona.ifig Table XIII lists the partition coefficlents of a number of elements from aqueous solutions of varlous hydrofluoric acld concen- trations. Dibutyl ether ether as an extractant far uranium has been Investigated extenslvely by workers 1ln the Soviet Union;ifi&ii&éziig Di- butyl ether offers several advantages over dlethyl ether. It 18 less soluble in water, lees volatile, and has a hlgher flash point. The dietributlion coefflclent of uranyl nitrate is, however, less for dibutyl ether than for diethyllether. The partitlon of uranium between water and dlbutyl ether ds represented in figure 1.222:32L Mo dqigtribution of uranyl nlitrate and nitric acld 1s plotted as a functlon of agqueous nitric acld concentration in flgure 16.§£§ Karpacheva, Khorkhovina, and Agashkin&iig have 8tudled the effect of varlous salting-out agents on the distributlon of uranyl nitrate. The salting-out actlon was found to lnerease wilth increasling valence of the catlon. The partlition coefflclent of -uranium from an aqueous solution initially 0.5M fiOE(Noj)a, 4.5M Cca(WNO o» and 0.5M HNO, into an organic phase 85% (by 3) 3 volume) dibutyl ether and 15% carbon tetrachloride is 0.70; %py (VT) is 0.42.331 Zireonlum, nioblum, and ruthenium are the main flsslon product elements ext::fla,n:-..ted.—efi&ij&g Heyn and Ba.ne::"jee;a-29 have studled the extractlon of blsmzth nitrate by dibutyl ether and several other solvents. 93 URANIUM PARTITION COEFFICIENT 1.0 I I I 1T I ! I . I | ] A < - " ) H.QE& X Q, Q, ¢ : 6b : .404, 7/ _ 0.1 | "o - - g ] - 0.02 — | —l ] 1 l_. ] O ! 2 3 4 9 6 ¥ INITIAL AQUEOUS NH4qSCN GONCENTRATION, M Flgure 15. The extractlon of uranyl thlocyanate by dilethyl ether at various inlitilal NHusCN and HC1 concentrations. After R. Bock, reference 341, Conditlions: Aqueous phase--initially 0.1M, U0O,Cl., and NH,CNS and = 4 HC1l concentratlion indlcated. 272 Equal phase volumes equilibrated at room temperature. 94 Table XIII.- Partition Coefficlents of Varlous Elemente between Aqueous. HF Solutions and Diethyl EtherZ HF concentration of the stertlng aqueous solutlon Element— 1.OMHF 5. OMHF 10.0MHF 15.0MHF 20. OMHF Sb(T1L) <0.0005 0.003 ' 0.019 5,000 0.0067 As(IIT) 0.111 0.227 0.432 0.530 0.605 As(V) <0.001 0.017 0.048 0.121 0.157 Be <0.0005 <0.0005 0.005 0.019 0.042 cd <0.0005 0.002 0.006 - 0.009 0.014 Co <0.002 - €0.002 <0.002 0.005 0.017 Cu(II) <0.001 <0.001 <0.001 0.010 0.013 Ge(IV) <0.002 <€0.002 0.005 0.028 0.072 Mn(IT) <0.0005 <0.0005 0.002 0.005 0.013 Hg(IT) <0.0005 <0.0005 <0.0005 0.009 0.028 Mo(VT) 0.007 0.018 0.031 0.062 0.103 M <0.0005 ¢0.0005 <0.0005 0.005 0.007 Nb(V) 0.006 0.04% 0.480 1.08 1.92 P(V) <0.001 0.011 0.032 0.110 0.173 Re(VII) 0.0005 0.121 1.58 1.78 1.62 Se{IV) 0.0006 0.022 0.080 0.131 .0.148 Ta 0.012 0.774 - 3,80 3.82 3.84 Te (IV) 0.0001 0.020 0,071 0.237 0.298 Sn(II) 0.020 0.029 0.052 Sn{IV) 0.006% 0.0062 0.053% 0.055 U(v1) <0.002 <0.002 <0.002 0.005 0.011 v(IIT) <0.0005 0.003 0.03 0.10 0.13 v(V) <0.001 0.004 0.017 0.056 0.093 Zn €0.001 <0.001 <0.001 0.002 0.009 Zr 0.004 0.005 0.005 0.012 0.030 & After Bock and Herrmann, reference 342. Equal phase volumes equilibrated at 20.0 * 0.5°C. E-The concentration in the 1nitlal aqueous solution of the lonlic specles of the element listed in the table was 0.1M in each case with the exception of Re(VII) which was 0.05M. Fluoride stock solutlons were prepared 1n the following menner: carbonates (Cd, Co, Cu, Mn(II), Ni, 2Zn), oxides (Sb(III), Ge(IV), Hg(II), Nb(V), Se(IV), Ta(V), Te(IV), V{III)) or hydroxides or hydrated oxides (SN(IV), Zr) were dissolved in an excess of HF; As 03 was dilssolved in a known volume of O.1N NaOH and the calculated amount of HF added to the solutlon; BeF2 and SnF2 were dissolved; K HAsOu, Na2HP04, KReou, ammonium vanadate, ammonlum molybdate, and sodlium uranate were dissolved 1n HF. ' 5.4 M HF £ 10.4 M HF 95 1.0 — -3 z - : w [ HNO3 - ) = @ o TR uw B { o O z O. UOp(NO3)e _ o ] e - o g a oo L—1L 1 1 1 ¥ 1 1 1 1 '} 4 3 @8 7 8 © 10 1 12 13 14 15 16 INITIAL AQUEOUS NITRIC ACID CONCENTRATION, M Figure 16. Partitlon of urenyl. nltrate and nitric acid between dibutyl ether and aqueous solutlon. After V. Vdovenko, A. Ilpovskll, M. Kugzina, reference 346, Conditions: Equal phase volumesa equlllbrated at room temperature for both UOo({NO3)o and HNO, extractions. For nitric acid, polnte corr&aponding tg an acld content In the aqueous golution of greater than 13.4M were obtained by the ex- traction of previously aclidified dibutyl ether wlth con- centrated nitric acld. For uranyl nitrete, polnts greater than -12.0M HNO7 were simllarly obtalned. The uranlum concentration ¥%as 78 mg/ml. : Dibutyl "Cellosolve" (Dibutoxymonoethyleneglyocol) Aqueous nitrate systems. A number of cellosolve derivatives have been lnvestligated for the extraction of uranium (Table VIII). Diethyl cellosolve 18 an excellent extractant;iig Unfortunately 1ts solubllity 1in water 1s large (21% by welght at 20°C). Dibutyl cellosolve 1s less soluble in water (0.2% by welght at 20°C). However, 1t does not extraot uranium as well as dliethyl ether, either from water 96 solutlon (figure 2l§543§l) or from aqueous alumirum nitrate solution (figure 6112). The partition coefficlent of uranium into dibutyl cellosolve from nearly satureted solutlona of ammonlum, calcium, or ferrlic nltrate 1s 1, 50, and 20, :n-.e.-apectil.\rely.-332 Dibutyl "Carbitol" (Dibutoxydlethyleneglycol) Aqueous nitrete systems. Dibutyl carbitol (Butex) is used in the recovery of irradiated fuel material.fiil As a Bsolvent, 1t has ‘been subject to conslderable st:udy.a:g-'-352 The partition of urenium between water solution and soclvent 18 glven 1n figure E.EIQngilfigl The partition of uranlum between nitric acld solution and dibutyl carbltol 1s 11lustrated in figure 17.353 For aqueous solutlons in this range ol acld concentration, the partition coefficient 1s observed to 1lncrease with increased uranyl nitrate concen- tration. The partition coefficlent of nitric acld 1s plotted as a function df acld concentration in figure 18.-33’—4'-"-353-'-3-5-i In figures 19 and 20, the partlitlon coeffliclentes of uranlium and several other heavy elements are plotted against nitric acld concentration. The 1nitiel acld concentration of the aqueous phase 18 plotted 1n figure 19.33& The equllibrium acld concentration of the aqueous phase 1s glven in figure 20.3£E Best, et hl-352 have observed that the ateephess of the extractlion ocurves (figure 20) 1s compatible with the formetlion of the specles HM62(N03)3 and H2H(N03?6 in the organic phase rather than Just Hoa(Nos;)2 and M(NO3)4. The curves glven 1n figures 19 end 20 are 1n general agreement consldering the dlfference ln acld concentration plotted. There 18 a large discrepancy between Np(IV) data. The abllity to malntaln neptunium 1ln the pentavelent state during extractlion mey be subJect to question. The partitlion of some fisslon product elements 18 given 1n figure 21 fop various 97 1.0 2 > u - s E D.I —: o j w - u — S . O ! Flgure 17. Distribution of uranyl nitrate J between dlibutyl carbltol and nltrlc acld g golution. Adapted from C. A. Kraus, - reference 353. Conditlons: Approxlmately - 0.01 b _ equal volumes of organlc and agueousg - v ; - phase, 1lnitlaelly at the uranium and nitrlc nq"' - acld concentrations 1indlcated, equlllbrated o 7] at about 27°C. - fi 0.00lI T | L I i I I r 1 ! & o llo ' . > - T _ -g o - - . 4 h- > - w 9 L. W W Q. o * 3 o ] 2 - ° - - - & o " ] a 0.0l | | 1 ] ] ] ] 1 ] 1 o I e 3 4 85 8 7 8 9 10 Il INITIAL AQUEOUS 'NITRIC ACID CONCENTRATION, M Figure 18. Distribution of nitric acild between dibutyl carbitol and aqueous solutlon, O, After C. A. Kraus, reference 353. 0, After J. Kooil, rfiferfince 334, A, After D. G. Tuck, reference 354. Conditions: Equal334,35% or ap- proximately equa.1355 volume portions of solvent and agueous solutilon equilibrated at ~27°¢,353 250C,334 and ~21°C.354 100 T | ! I 1 ] | | I 1 ; ———-- Pu(IV')': ] : . 9F NptV) e C Pu(VI) ] w = - O - u(vI) 7 L - 4 e i ™av)/ 3 g NP(V) 3 Z - i O - _ T Np(1V) - i @ | a C.l = 'E r : I ; | O I 2 3 4 5 6 78 9 10 11 I2 INITIAL [HNOgloq, M _ Flgure 19. The extreotlion of actinlde nitrates by dibutyl carbltol. After J. Kool, reference 33L4, Conditlions: Tracer -amounta of Np239 or Pu239, 330 mg of Th(No3)4 4Ho0 per 15 ml, or 300 mg of UO2(NO3)o (hexahydrate) per 15 ml in aqueous nitric aclid solution equlllbrated wilth an equal volume of dibutyl carbitol at 25°C or room tem- peraturs. The oxidatigfl states of neptunilum have been the subject of some question.33D 99 OO —r——T——T7T—TT1T T T T T T T T Tirl O = oy & L1l a o T 2 9 s L1 / Np{Vi) A Pe(Vi) 1 LUV T 1/ Th{IV) PARTITION GOEFFICIENT, o o I 1 IIIIII ] IJJIIII- | | | | ] 6 7 8 9 10 1l [HNOz]sq. M Flgure 20. o.o0 L4 LI Pt 1 O I 2 3 4 5 The distribution of actinide elements between dibutyl carbiltol _and aqueous Bolutlon as a function of equilibrium aqueous nitrie acld concentration. After G. Best, E. Hesford, and H. McKay, reference 345. Conditions: Tracer concentretions (~10'3§) of actinide. Temperature, 25°C.. 100 G PARTITION COEFFIGCIENT, 1.0 T— T 1T T T T T 1 T 1 3 - 3 [ 1 107 = A Ce(IV) 5 r - i ) 0% |- 3 : A Ge(lll) ] i Y |(y-3 = — - . - ] o4 L—L 1 111 0 | 2 3 4 5 6 7T 8 9 10 11 12 [HNO3Joq. M Flgure 21. The partlitlion of tracer samounts of yttrium, cerium, and zlrconlum between dlbutyl carbltol and aqueous solutlon as 8 functlion of aqueous niltrlc acld concentration. After H. McKay, K. Alcock, and D, Scarglll, reference 355. 101 10000 c—1T——T—7——T—T T T T T T T T 3 =. © 1000 | - - 2 - wl G ] E b W o - Z _ o i ~ | = < 10 | o F _ o b—1 0y 4 5 6 7T 8 9 1011 12 13 14 15 16 17 EQUIVALENTS OF METAL NITRATE per 1000 ¢¢ OF WATER Figure 22. The effect of salting-out agente on the extractlon of uranium by dibutyl carbitol. @ Cu(N03)p, ®Ca(NO3)2, & Zn(NO3)z, 0 A1(NO3)3, l:l_Fe(NOg)g, A 1a(NO3)3. After E. Evers and C. Kfaus, reference 332, Condifions: Urdnlum concentration, 2-6 g/100 cc of phase. Temperature, 279C; Vo/Va = 1. X Al(N0353. After D. Lee, R. Woodward, G. Clewett, reference 358. Conditlona: Trace amounts of uranium. Temperature, 27°C; V,/Va, variled. aqueous nltrlc acld c:onr:s.-ni;zz-e.i:.ti.onisl.-3"22 The dlatribution of iron into dibutyl carbitol 1s increased by an lncreage 1n a.c::l_d:l1‘:y.§-5—g Chloride ion promotes the extraction of iron. Boron 18 extracted by butex, especlally 1in the presence of copper nitrate as salting-out agent.aaig Vanadlum and molyp- dermum are extracted to several per c:en‘v:,.-a-2 The extractlon of cadmlum. chronlum, nlckel and tltanlum 1s small.d32 102 The effect of Ba;ting-out-agenta on the distrlbution of uranium into 4ibutyl carbltol has been Butdied.iigiiég’ 356-358 Some of the results are presented in filgure 22. Aqueous_chloride systems. Uranium (IV) and (VI) and thorlum are poorly extracted by dibutyl carbitel from aqueous solutiofia 2-6M in hydrochloric acid.§§2 The extrac- tlon of protactinlum 1s Increased as the acld concentratlion 18 1ncreased. From 6M HC1, ap, 18 10. The extraction of _hydrochlorie acid 1s negliglble from agueous solutions less than-fifl i1n hydrochloric acld. A thlird phase 1s formed upon equilibration with 7.5M HC1l. The third phase containe a large amount of the aclid., One phase resulte upon equlllbra- tion with 8.5M HC1. Pentaether (Dibutoxytetraethyleneglycol) mich of the data pertinent to the extractlion of uranlum by pentaether. The distrlbution of uranyl niltrate between solvent and water 1is glven in figure EAlzéiigi The partl- tlon coefflclent of uranyl nitrate from varlous nitrate medla ls plotted in flgure 23.—3-§g The dlstributlon of nltric acid as a function of aqueous acld concentration 1s also shown 1n flgure 23.§§£ The effect of palting-out agents on the partition of uranium is 1ilustrated In filgure 24,532 Table XIV 1lists the partition coefflcients of a number of elements other than uranium between pentaether and various aqueous med:!.a..—3--ég Uranium 1s éxtracted by pentaether from aqueous solutions contalning ammonium nitrate and/or nitrilc aclid in the presence of sulfate, phoaphate, or sillcate 1::m&1.4§§g Phosphate 1lon, in large quantity, and soluble sllicate lons are extracted by the solvent.iég Fluoride ion, in signifi- cant quantity, lnterferes with uranyl nitrate extraction. This effect may be overcome by compiexing the fluoride ion with calclium or aluminum n:Ltz"::aLte.-:?:é2 103 o llllflli o~ | UOg(NOa)z: 5¢ NHqNOz /10 mli| —t_ -0 HN03 IJ_lllll 0.1 PARTITION COEFFIGIENT, a _I_l_l_llLlI : ] ] I | L 1 1 ! ] o | g 3 4 % &8 T @ € 10 H 12 INITIAL AQUEOUS NITRIC ACID GONGENTRATION, M Flgure 23. The partition coefflclents of uranyl nitrate and nitric acld between pentaether and agueoue solution. A UOQ(NO3)2 : 1.0 g. Ugoa dlssolved in I-]N‘O'i;, dlluted to 50 ml with acid of depilred strength, and shaken 1l minute wlth an equal volume of pentaether. D_UOZ%NO3)2 + NHyNOg : 1.0 g. U308 dipsolved in 10 ml of ENO3 of deslred strength af%er addition of 5 g. NH4N03; shaken with an equal volume of pentaether for 1 minute at room temperature. Adapted from D. Musser, D. Krause, and R. Smellle, Jr., reference 360. OHNO3 : equal volumes of nltrle acld solutlon and pentaether equilibrateé f‘gr 1 hour at 259C. After C. Stover, Jr. and H. Crandall, reference 361. Cyclic ethers. A number of cycllc ethers have been investigated as ex- tractants for urand.um.M Those solventls that contaln the furane nucleue have been found to glve good extractlons of uranyl nitrate from aqueous solutions. Solvents of the hydrocarbor substltuted tetrahydrofurane type have been found to be eppeclally good.-lsj- The extractlon of uranium and thorifim by four cyclic ethers 1s 1llustrated 1in figure 25 a8 a function of acld concentration 1in the agueous phase.is—lt 104 10000 c—T— T T 1 o P- z W 1000 S u 1R ad o o z o = 100 - e Lo a. ob—L 1 1o b 3 4 5 6 7 8 9 10 Il 12 13 14 1% EQUIVALENTS OF METAL NITRATE per 1000cc OF WATER Flgure 24. Effect of salting-out agents on the extraction of uranium by pentaether. AN‘aNOgr V NH4yNO3, ®Ca(N03)p, OA1(NO3)3, QFe(NO3)3. After E. Evers and C. aue, refeéerence 332 Condltions: Uranlum con- centration, 2-6 g/100 ce of phase. Temperature, 279C or room tempera- ture. ' From figure 254, 1t can be seen that uranyl nitrate 18 ex- tracted more efficlently by the varlous solvents than ls uranyl perchlorate. Better separation of uranlium and thorium 18 also sachieved from nlitrate solutlion rather than perchlorate. ESTERS Information 18 leas complete or less readlly available for the extractlion of uranlum by esters than by ethers. The dletributlion of uranyl nitrate between ilso-amyl acetate and #ater 1 represented 1n f.’igu::'e_'}-fl..l-a-2 Karpacheva, et a1,iflg have found the extraction capaclty of butyl acetate to be Intermedlate between dlethyl ether and dibutyl ether. Hyde and Wolf,ilé in addition to thelr 105 Table XIV. Partitlon Coefficlents of Elemente between Penta-ether and Various Aqueous Medial Element Concentration in Aqueous m:nlut—:tonE agqueous phase before extraction Nitrate Nitrate + Sulfate Sulfate (mg/25 m1) Chloride + Chloride Al 500 0.003. 0.003 0.000 0.003 Ba 362 0.02 " 7 0.35 cd 501 0.024 0.003 " 500 0.026 n 10 0.053 0.01 " 10.5 0.004 Ca 521 0.011 _ - c " 500 0.0001 —c " 10.4 0.020 0.00 cl 496 0.026 n 4ol 0.02 " 10.3 0.025 " 9.9 0.03 Ccr(III) 500 0.003 0.004 0.0001 n 10 0.0023 0.013 0.000% Co 555 0.007 " 500 0.002 0.00013 " 11 0.012 n 10 0.009 0.0065 Cu(II) 500 0.026 0.024 0.000 " 10 0.017 0.018 0.000 Fe(III) 515 0.031 0.003 " 500 1,2 " 10.3 0.035 0.002 " 10.0 0.046 Pb 500 0.017 --c " 10 0.007 0.005 Mn(II) 500 0.0011 0.00006 n 10 0.0014 0.00075 Hg(II) ha7 ' 0.21 0.015 " 127 0.19 0.036 " 10 0.41 0.176 0.23 0.03 Mo (VI) 500 0.028 0.10 0.001 0.001 n 10 0.10 0.015 106 Teble XIV. - Continued Element Concentratlon in Aqueous 8011.1'|.'.-:|.on'-E agueous phase before extraction Nitrate Nitrate + Sulfate Sulfate (mg/25 ml) Chloride + Chloride N1 516 0.0001 " 500 0.0018 " 10.3 0.0008 " 10 0.0032 0.00064 P(P0}" ) 500 0.00005 0.00001 " 10 0.00024 0.00 Ag 500 0.09 0.005 " 10 0.32 0.005 sof* (aa(NHu)asou) 500 0.00 " 10 0.00 Th 500 9.12 11.5 0.0001 0.0001 " 10 87.5 0.005 Sn{IV) 500 0.0024% 0.37 0.00015 0.000 " 10 0,019 0.0006 T1(IV) 11 0.003 0.00 0.035 W 10 0.081 0.0025 v(V) 140 Q.22 " 107 0.11 " 14 0.12 " 8.5 0.07 0.009 Zn gy 0.15 n by 0.018 n 10 0.14 --c " 8.9 0.022 0.000 Zr 10 0.04o 0.013 2 Adapted from A. G. Jones, C-4.360.3(1945). Equal volume portiona of aqueous solution and pentaether, 2 Niltrate Sulfate Chloride: present. : 3/4 saturated ammonium nitrate solution. : paturated ammonium sulfate solutlon. chloride added as ammonium chlorlde equlvalent to the metsal L Preclpitates of insoluble sulfate obtalned 1n ammonium sulfate layer. 107 10 | | | ] ] 1 | ] | ‘Uronium ] 1 lIlIlI L - 3 z - w - 2 ] = T w o o z 1 T ° Thorium 2 « = == HCIO4] q L o 1 IILlLI 0.01 = ! i Py 0 | 2 3 4 5 6 T 8 9 10 H INITIAL AICD CONCENTRATION, M (B) Flgure 25. The effect of inltlial nltric and perchlorilc acid concentra- tlon on the extraction of uranyl salts (Fig. 25-A) and thorium salts (Flg. 25-B) by tetrahydrosylvane (THS), tetrahydropyrane (THP), 2- ethyltetrahydrofurane (ETHF), and 2,5-dimethyltetrahydrofurane (MTHS). After M. Branlca and E, Bona, reference 364, Conditlons: Uranium concentration, 2 x 10_—3@. Thorlum concentration, tracer UX;. Tempera- ture, 25 + 0,20C. Vo/Vg, 1. o 108 general survey work (Table VIII), have studled the extrac- tlon of thorlum and uranium by ethyl acetate, n-propyl acetate, and l1lso-propyl acetate as a function of the nitrate concentration of the agueoue phase. It was the observatlion of the latter groupglé that the extractilon of uranlum tends to decrease wlth 1ncreasing molecular welight of the esater. Therefore, only acetates and proplonates need To be consldered serlously. Increased protactinum extraction was observed wlth incfeasing length of the alcohol portion of the ester.ilg It was further observed that hydrolysls of the ester tends to lncrease the extractilon of both thorlium and uranium.ilé It was not determined whether the addition of alcohol or organic acild causes the 1ncreased extractlon. Ethyl acetate nltrate between ethyl acetate and water has been studled by deKeyser, Cypres, and Hermann.lé& The partition coeffiliclent was found to vary from 0.17 at 22% UOE(NO3)2 . 6H20 in the aqueous phase to 0.78 at 43% aqueous concentration. In laboratory practlce, uranium 1s extracted by the solvent from aqueous nitrate medla. The followlng conditlons have been ueed by varlous groups to extract uranium: Grimaldl and Levine3®2: 9.5 g. of AL(NOg)5 - 9HLO are added to 5 ml of solutlon approximately 2.4N in HNOS. 10 ml of ethyl acetate are added and shaken at least 30 seconds. Rodden and Tregonningiéé: Uranium preclipltated 1n the presence of aluminum (20 mg) wilth NHMOH l1s dlssolved in 1 ml of HN03(1 to 1). 8 g. of Mg(N03)2 . 6H20 18 added and the volume adJusted to 10 ml with water. 5 ml of ethyl acetate are added and vigorously shaken for 2 minutes. (Used with 20-400 mg samples of U308') 109 Nietzel and DeSesa32l2368. approximately 15 ml of sat- urated alumlnum nltrate solutlon are added to 3 ml or leas of sample containing 0.30 to 15 g. of U308 per lliter. 20 ml of ethyl acetate are added and sahaken for 1 mihute. Guest and Zimmermanfiég: To 5 ml of sample contalning 5% concentrated HNO3 by volume, 6.5 ml of hot alumil- num nitrate solution, having a bolling point of 130°C,, are added. The resulting solution 1s cooled, 20 ml of ethyl acetate are added, and the mlixture shaken for 45 to 60 seconds. Steele and Tavernerlgg: Approximately 5 ml of aqueous golution are saturated with alumlinum nitrate. The resulting solution 1s shaken with 10 ml of ethyl acetate for 1-2 minutes. In the procedure of Rodden and Tregonning,iég aluminum ni- trate 1s used lnatead of magneslum niltrate 1f extractlion i1s to be made 1n the presence of phoasphate. DeSesa and NkfizeliéZLiég found that 1 molar concentratione of phos- phate, sulfate, or carbonate ion could he tolerated with no 111 effect on uranium extractlon. Small amounts of godlum phosphate have been used to suppress the extractlon of thorlum wlthout affectlng the extraction of uran:l.um.-l-2§ Steele and Ta.ver'nerlgg report the extractlon of apprecilable amounts of thorium and zirconium and small amounts of vanadium, molybdenum, and platlinum by ethyl acetate. Grimaldl and Lev:l.ne,iéflli Guest and Zimmerman,§§2 and Nletzel and DeSes&iéILiég have lnvesatigated the effect of a number of elements on the recovery and/or determination of uranium according to thelr respective procedures. Nletgel and DeSes&iéZLzég-found vanadium, present in 100 mg amounts, was precipltated and uranium was occluded 1n the preclpitatate. Titanium was observed to partially extract. This was pre- vented by preclpltatlion of titanlum wlth p-hydroxyphenylarsonilc acld before extraction. procedure in which uranium is extracted by ethyl acetate from an aqueous phase contalning an excess of ammonium thlocyanate. Dizdar and O‘I:I-enov:chl'?-'l have'also Inveatlgated the extraction of the uranyl-thlocyanate complex by ethyl acetate, KETONES Methyl ethyl ketone. nitrate between methyl ethyl ketone and water and between methyl ethyl ketone and saturated ammonium nitrate solutlon is glven in figure -, 321 E’ale::l.-]:gé reports a uranium partition coeffleclent of approximately 25 between methyl ethyl ketone and an aqueous solution of 60% NH4N03 and 1N HN03. Methyl ethyl ketone is not as selecfive as diethyl ether'.—3-gl Homogeneous sclutlons are formed be- tween the ketone and an equal wlume of saturated ferrilc or cupric nitrate at 20°C.BgL clent of uranium between methyl ethyl ketone and an aqueocus GO%INH4N03, 3% NH,SCN solutlon 1s about 2000.i2§ Iron 18 extracted. Milner and ‘Woocl—-?iZg report the separation of tantalum and nioblum from uranium by extracting the fluorldes of the former elements wilth methyl ethyl ketone. Hexone (Methyl iso-butyl ketone). between hexone and water 18 represented 1n figure 4.18 321 The partltion coefflcients of uranium, nitrlc acld, and several other actinlde elements are plotted as a function of aqueous nitric aeid concentratlion 1n flgure 26.—3-3-E The effect of several salting-out agents on the partlition coeffl- 111 PARTITION COEFFICIENT, a 10 — T T T T T T T T T T 3 - _ Pu(IV) 3 l e Np(V) - ~ Pu(VI) 7 - U{vl) 7 1.0 . — " " . 0 o SR HNOaf - Th(IV) ] X Np(Iv) T 0.1 :— "-l. — 0.01 l l I | | 1 i | ] | | 0 ! 2 3 4 S5 8 T e 9 IiC 11 12 INITIAL NITRIGC AGCID GCONCENTRATION, M Flgure 26. The extractlon of nitriec acid and actinide nitrates, Th, U, Np,and Pu, by methyl isobutyl ketone (hexone). After J. Kool, reference 33i4. Conditions: Tracer amounta of Np232 or Pu239, ?30 mg of Th(NOg), ° 4Ho0 per 15 ml, or 300 mg of U02(NO3 )5 (hexahydrate§ per 15 ml in nltric acld solutlon of nitric acid alone equllibrated with an equal volume of hexone at 25°C or room temperature. The oxidatlion atfitea of neptunium have been thé subject of some question.3%5 112 clent of uranlum 1s given 1n f:l_gu're.e'r.-—i12 Vdovenko and co—workerazgé have obsBerved an increase 1n the partltion coefficlents of ceslum, calclum, strontium, and lanthanum when the uranyl nitrate concentratlon 1n the 1nitilal aqueous solutlon 1le increased. This has been related to the extraction of the elements as metal uranyl trinltrate salts. The partition coefflcient of uranium from a highly palted aqueous solutlon is decreased by an 1lncrease 1n uranium concentration. Kra.us311 observed a, to decrease from 153 to 78.3 aB the 1Inltlal uranlum concentration was increased from 5 to 100 grams 1n an equeous solutlon con- taining 580 grams of aluminum nitrate. Jenkins and IWIcKa.y-iI-'!i found a. to decrease from 1.58 to 1.28 as the Initlal uranium concentration was increased from 144 to 348 grams per liter in an aqueous solution 8M in NH4N03 and 0.3N 1n HNO In 3 the latter case, commerclal hexone adJuated to 0.15N HNO3 was used as the extractant. Flgure 28 represents the ex- tractlon of uranlium by hexone from aqueous solutions contalning various amounts of nitric acid and calclum or ssod:!.um'n:L‘c,raLte.:’-Zi The distribution of U(VI), Pu(VI), Pu(IV), Th, La, Ca, Na, and HNO3 by hexone from aqueous solutions contalinlng nltrilc acld and calclum nltrate has been lnvestlgated by Rydberg and Bernstrgm.§Z§ Hyde and co-workers have studled the extraction of uraniumiié and thorlumélélizz by hexone as a function of the total nltrate concentration of the aqueous phase. Dlistri- bution curves (a or P versus nitrilc acld or total nitrate concentration of the agueous phase) are presented for the varlious elements in the different papers. The effect of alumlnum nitrate concentratlon on the extraction of fiaslon product gamma-actlivity 1n general and zirconlum-nioblum, cerlum, and ruthenium in particular 1s shown in flgure 29.§I§— Increased extractlon is effected by an increase in salting-out agent. An increase 1n nitric acld concentra- 113 1000 [ ] o - 100 - - ;] n 3 = ™ S o - i _ i = . - o 5 10k 3 w - ; L. L = w | i - . o [ g A e L —_ - 1.0 = 3 = C ] ‘é - . a. L . - . 0.1 — = s . | a oot b—d 1 1 1 111 )11 1| o1 2 3 4 5 6 7 8 S 101 12 13 NITRATE CONCENTRATION, M Flgure 27. The effect of varilous saltlng-out agents on the extractlon of uranium by hexone. V NO3, mNaNO3, DCa(NOi)g, A Co(NO3)2, & Mg (NO3 )2, oBe(NOi-;)g, O Al( 03?2. After W. H. Baldwin, referénce 319. Condltlions: Egual volumes of pure hexone used to extract aqueous con- talning 30 g U/liter. ay PARTITION COEFFICIENT, o 1 1T 11hi _ ] \\\ — W) W\ v\ v N ] | > o ” 1;4- .0 - NaNOy ; NO3 e -1 | 107 = | | | | 1 3 0 I 2 3 4 5 6 NITRATE GCONCENTRATION, M, OF SALTING-OUT AGENT Figure 28. The partition coefficlent of urdnium as a function of the nitrate concentration of the salting-out agents, Ca(N03)é and NaN03, for an 1nitlal concentratlon In the aqueous phase of 100 g/1 of uranium and 1,2,3, or i4M HN03. After A. Cacclari, R. Deleone, C. Flzzottl, and M. Gabaglio, reference 375. tion also causes an lncreased extractlon of fisslon products (figure 29).§Z§ The extractlon of uranium by hexone is facilitated by the presence of substltuted ammonlum nitrates whlch are sufflclently soluble in the organlc solvent. A number of these salts and thelr effect on the extractlion of uranium are listed In Table XV.Z2 Tri-n-butylamine, 2-hexyl pyridine, and dlbenzoyl methane lncrease the extraction of fission products.izg Maeck,lgg;gl.ilg have lnvestligated the extrac- tlon of uranium by hexone from an aqueous solutlion con- taining aluminum nitrate and tetrapropylammonium nitrate. The extractlon condltlons adapted as a result of the 115 10 l | I " oapM HRO 3 - 0.3M HNO3 : | / QEE s ] y / | S . F‘ — = Ll - o C.1 E i 3 m 1 Q - o — > Fission o * Product _ = 0.0 y-Activity] E - 0.0M HNO, . o - “””f‘f’ ] o | i 0.00I | 0.1 Bass | = - Zr-Nb / ] I ] 1 i ] 1 . | 0.000 o l 2 3 4 5 6 ALU' INUM NITRATE CONGENTRATION, N Figure 29, The effect of salting-out agent, A1(NO3)3, on the ex- tractlon of uranium and fission products by hexone fPom aqueous solution at varlous nitric acild concentratlons. After F. R. Bruge, reference 378. Conditlions: The results on uranilum and gross flssion product activity were obtalned using G.P. A1(NO3); as sdlting-out agent and pretreated hexone as solvent. Rn lrradlated uranlum slug, cooled 144 daye and dissolved in HN03, was used as activity source. Extractions were made at 30°C from an aqueous phase oxidized 1 hour wilth 0.1M NasCr O7 at this tempera- ture. The nitric acld 1s the sum of %hat-in the -aqueous and organic phases, expressed as moles of nitric acid per liter of aqueous phase, Ruthenlum extraction:aqueous phase--0,1M K,Cry07, 0.2M I-]INO3, Al(N03)3. Cerlum extractlion:aqueous phase--o.oesfl Na, HNO,, AJ.(NO3)3. Zirconlum-nioblum extraction:aqueous phaae--O.lfl_KQC 0.25E'HN03, 8 g U per liter. 20T 0,, 0.5M 116 Table XV. Effect of 3ubstituted Ammonium Nltretes (RNOB) on the Rxtraction of Tlranyl Nitrate by-Hexone-E Catlion, R Total RNO3 o - concentratlion (mol/1 x 103) None 0 2.62 (C,H,) NH 2.1 6.2 479’3 4.2 10.7 11.0 32.4 21.0 68 (C.H,. ). NH, 2 2.5 6.0 8717’2 5.0 g.u 10.0 15.5 ' 20.0 33 c Ng £ 2.0 5,4 11%5" 5.0 13.4 10.0 26.7 20.0 57 Cq H.,N.H 2.1 5.5 1272472 10.5 25.6 (¢, H,) N 10.0 a7 479k 10.0 gl C gH, NH & 10.0 2.8 (02H5)3NH 10.0 4.0 (CH20H2OH)4N 10.0 2.67 After Kaplan, Hlldebrandt, and Ader, reference 78. Condltions: equal volumes of hexone and of an aqueous solution. 8M i1n NHyNO3, 0.4M in HNOg, and about 0.02M in uranyl nitrate. o o dl-2-ethylhexylammonium o 2-n-hexylpyridinium [=1 methyl isobutyl ketazinlium [] 2-methylpyridinium investigation were 4.0 ml of 2.8M alumirum nitrate, 1N acld-deficient, contalning 0.1%(weight/boiume) tetra-~ propylammonium nitrate; 2.0 ml hexone; and a sample slze of 6.5 ml (~2 mg of uranium). These conditions provide a good separatlion of uranium from many lones. The separatlion from zlrconlum-nicbium 1s particularly good. The recovery 117 of uranium is excellent even 1n the presence of foreign anions (10 to 1 mole ratlo of anion to uranium). Of those aniona tested, tungstate lon lnterferes most seriously (only 64.28% uranium extracted). Chloride, sulfate, phos- phate, acetate, oxalate, etc., in the amounts tested, exhibilt no appreclable interference in the extraction of uranium. Chloride doesa promote the extraction of those ions which form anlonlic chloride complexes, eg. gold (III)}. Certain other anlons enhance the extractlon of fisslon producte, eg. dichromate and thiosulfate lncrease cerium extraction. by hexone from aqueous thiocyanate solution.zziiigg Reas3§9 has investligated the separation of firanium and thorium by thils means. Some of hls results are given 1n Table XVI. The effect of sulfate ion (experimental conditions B) 18 to hinder the extractlion of both thorium and uranium. The effect, however, l1ls greater for thorium than for uranium. Consequently, greater separation of thorlum and uranium can be made 1n the presence of the complexing sulfate i1on. The extraction of protactinium from an aqueocus solutilon 1.2M in NHyNO;, 0.20M in HNOg, about 0.01M in Th(NO;),, O.00987M in Naesou, and 0.501M 1n KSCN by an equal volume of hexone was < 4.4%. Decontamination from fission products is not too good. Equllibration of equal volumes of hexone and an aqueous solution approximately 0.04M in UOE(N03)E’ 0.504M 1in Th(NO,),, 0.485M in Na,S0,, and 1M in HNO; resulted in a beta decontamination factor of about 6.6 and a soft gamma decontamlinatlon factor of about 1.5. Zlrconlum was found to be the principal filssion product extracted. Methylcyclohexanone égueous nitrate systems. This solvent has been studied 118 Table XVI. Separatlon of U(VI) from Th(IV) by Thlocyanate Systems,2 Experimental condltions KSM U extracted Th extracted M % : % A 0.27 64.5 1.03-1.6 A 0.54 82 1.5-1.8 A. 0-9‘? 89-5 2-1-3.1 A 1.62 95 5.2-6.2 A 0.32 + 0.11M 79 3.3 antipyrine * 0.501 63 0.14 B 0.25 35 0.015" & After W. H. Reas, reference 380. Experimental condltlons: : A: 0.16M U02(NO3)p, 0.81M Th(NO3)Ly, volume of aqueous phase = %.2 ml, volume of hexone = 10 ml. B: 0.0974M UOp(NO3)o, 0.252M Th(NO3)y, O.2M HNOg, O.224M NaoSOy, volume o% aqueous phase = 10 ml, volume of hexone = 10 ml. The thorium extractlion was performed under slightly different conditlons 1n that NHyNOq was substituted for U0p(NO3)p. An lonium (Th230) Tracer was added to the solutlion and the dlstribution was measured by the determination of lonium in each phase. by workers 1ln Czechoslovakla as a means of separatlng uranlum from thoriumigi and fission products.égfiiigg The extracta- bility of uranium by methylcyclohexancne from sodium nltrate solution (6-8M) is considerably better than that of thoriumsot From nitric acld solution (BM), the extractabillity of uranium 18 only two- to three-fold greater than that of ‘r:ho::-:"u.lm.zgl Ammonlum nitrate 1s comparable to sodium nltrate as a salting- out agent for uranium.ggi Alumlinum nltrate l1s more effectilive than elther. However, the order of salting-out agents 1ln causlng lncreased flssion product extractabllity 1s Al > Na > NHu. The hest separatlion of uranlum from fisslon products 13 achleved wlth ammonium nitrate as the saltlng-out agent.igi Methylcyclohexanol present in commercial methyl- cyclohexanone suppressea the extractlon of uranlum and fisslon 119 products. The separatlon factor between the two actlvitles, however, 1lg lncreased slnce the partitlon coefflclent of fisslon producte 18 decreased more than that of m."an-il.u.m.—3-?-1 The partitlon of uranlum between methylcyclohexanone and water and methylecyclohexanone and 6M ammonium nltrate solutlon 18 given 1n figure 4-B.223 Other ketonle solvents dee and W‘olf-ilé have studled the extractlon of uranium and thorium by methyl n-amyl ketone and dlilsopropyl ketone as a function of total nitrate concentration 1n the aqueocus phase. In both casee, uranlum was better extracted than thorlum. The extraction of thorium did not become appreclable (¢5%) until the aqueous nitrate concentration was greater than 5M.. Dililsopropyl ketone was found to be -an excellent extractant of pr-ota.c'ls-:l.nil.um.-3l§ VEBelf, Beranové, and Mal{rzgg have 1nvestlgated the extractlon of uranlium and fisslon products by several methylalkyl ketones: methylhexyl, methylamyl, methlbutyl, and methylpropyl In addltion to methyl isobutyl and methyl- cyclohexanone. The partitlon coefflelents of both uranlum and flsslon product actilvlty 'vere measured as a function of acid concentration in the range of -0.4 to 3M nitric acid. In thla acldity range, fisslon product extraction was found to be maximum in the O-1M nitric acld region. The partition coeffleient, Apps i1n this region was greatest wlth methyl- propyl ketone (22 x 1073 at 0.61M) and least with methyl- hexyl ketone (2.4 x 1073 at 0.03M). In the acid-deflclent reglon, Opp Increased as the acid-defilclency was decreaaéd (the solutilon was made more acidilc). After the maximum Gpp Was reached 1n the 0-1M acid.region, the partition coefflicient was décreased and then increased as the aqueous solution was made more acldiec up to 3-4M. The partition 120 coefflcient of uranlum, 0,5 increased as the nltric acid concentration was Ilncreased over the entire range. At 3M nltrlc acld, o, varied from about 0.7 for methylhexyl ketone to about 2 for methylpropyl ketone and 3 for methyl- cyclohexanone. The greatest separation, B, of uranlum from fisslon products was found 1n the 0.1M acld deficlent reglon (-0.1M). For methylhexyl ketong B was found to be >1500; for methylpropyl ketone f was about 400. The extraction coefflcients of uranium were ¢ 0.2 for methylhexyl ketone afid about 0.5 for methylpropyl ketone at thils acid concentration. Allenigi has tested dilisobufyl ketone, dilsopropyl ketone, and methylhexyl ketone as solvents for the purifil- catlion of uranlum from iron, copper, chromium, and nickel. Diisobutyl ketone was found most satlafactory under the conditions tested. Dilsopropyl extracted some iron and chromlum. Methylhexyl ketone extracted 1lron, chromlum, end copper. Uranlum and thorlum may be extracted quantlitatively 384 from a nitrate medium by mesityl oxlide. Under the condl- tlons tested girconlum 1ls extracted to a large extent; vanadlum and yttrium to a lesser extent; cerlum only slightly. AT.COHOLS 316 Hyde and Wolf="— found alcohols to be only falr ex- tractanta of uranlum and the extractlon capaclty to decrease rapldly wlth the length of the carbon chaln. This 18 borne 385 out by the work of Poston, et al. who measured the ex-~- tractlon coefflecients of uranlum and ruthenlium as a functilon of alumlinum nltrate concentratlion of the aqueous phase for Experimental conditions: A salt of the elements tested was dissolved in 10 ml of HNO (15 + 85). DNineteen grams of alum- 1num nltrate crystals Were added and dissolved. The solutlon was shaken for 15 seconds wilth 20 ml of mesltyl oxlide. The extract was washed once wilth 20 ml of alumlnum nitrate solutlon and analyzed. 121 hexone and several tertlary alcohols: tertlary amyl alcohol, 2-methyl 2-pentanol; 2-methyl 2-hexanol, 2-methyl 2-heptanol. Only tertlary amyl alcohol extracted uranium better than hexone (0.5 - 1.5M Al(N03)3, o.e_n;fmoB) and all four alcohole extracted ruthenium better than hexone. Ruthenlum was extracted as well or nearly as well as uranium by the al- cohols. - Dilsobutylecarbinol extracts ruthenlum nearly as well as uranium.igé Thorium and zlrconium-mobium are poorly ex- tracted. Protactinlum 1as extracted much more efficlently than uranium. MISCELLANEOUS SOLVENTS Nitromethane has been recommended by.Warner-'igg as an extractant for uranium. It 1s reslistant to oxldation, Btable to hlgh concentratione of nitric :acid, and highly Belectlive. The dilstributlon of uranyl nitrate between nltromethane and water and nitromethane and saturated ammon- lum nitrate solutlon 1s given 1n figure 3-B. The extractilon of thorium nitrate by nltromethane from aqueous solution 1is mich less than that of uranlum. Color tests indilcate that neither copper, cobalt, iron III), nor chromium nitrate 1s extracted by the solvent. With dlethyl ether, considerable amounts of copper nitrate end trace-amounts_of ferrlic nitrate are extracted. Nitrilc acld enhances the extractlion of uranyl nitrate by nitromethane. However, above a critical acild concentration (~5§ Initlal acid concentration with equal phase volumes at 20°C) only one liquid phase 18 formed. ORGANOPHOSPHORUS COMPQUNDS. Within recent years, a large number of organophosphorous compounds have been developed and investigated as extractants for uranium. These compounds have-beefi gubdivided in the present paper into neutral and acldic organophosphorus compounds. 122 NEUTRAL ORGANOPHOSPHORUS COMPOUNDS Solvents 1lncluded 1n thls category are trlalkylphosphates, (RO) ;P - O; dlalkyl alkylphosphonates, (RO)RE -» 0; alkyl dialkylphosphlnates, (RO)REP-a 0; and %rialkylphosphlne oxides RBP-e 0. The abllity of the solvents to extraédt uranium is 1n the order (RO)3P-4 0 < (RO,)RP—> 0 < (RO)R,P— O <.RgP- 0. This 18 also the order of lncreaslng base strengths of the phosphoryl nygenfigg In Table XVII, the four types of compounds are compared as extractants of uranium (VI), plutonium (IV), thorium, fission products, and acids.§§1 It should be noted that although uranium is extracted almost quantitatively by tributylphosphine oxide (Table XVII), other elements are also hlghly extracted. 1In fact, in spite of lower extractlion coeffliclents, tributyl phosphate affords a better separation of uranium from thorium, plutonium (IV), and fieslon products under the conditlons listed In Table XVII than does trihutylphosphine oxide. Tebles XvItT200:3%9 ong x1x320 115t the atstribution co- =fficients of uranium and some assoclated elements for a number of neutral organophosphorus extractants. Simllar informetion on other solvents may be found 1n papers by Burser,égl Healy and Kennedy,lgg and 1n numerous ORNL reports. The latter have peen summarized by Blake, et al.322 and Brown, et alecs2392 The mechanlsm of extractlion by neutral organophosphorus reagents appears to be simllar to that of tributyl phosphate,égg’ 302,387 From nitrate systems, the extractlon of uranium by tributyl phosphate and trioctylphoaphlne oxlde 18 descrilbed fairly well by the equilibrium reactlon 25 - UOy™ + 2NOg5™ + 28 = UOE(NO3)2 (3)2, where S represents the solvent molecule.égg- Extraction may be made by tributyl phosphate from chlorilde solution. Stronger 123 ¥l Table XVII. Comparlson of the Extractive Capaclties of Various Types of Organophosphorug Compound&g Extraction of U02(NO ) Extraction of U, Pu, and Fisslon !Exgpaction of 3’2 Productaé lTh— Nitric acld concentratlon oM 0.6M 3M No added HNO3 0.6M HN03 U U - Acld — Acld | U Pu | Gross Uross Pu Gross| Grosa | Th ext'd| ext'q ext'd|ext'd| ext'd EVI) SIV) B T {VI}?IV) B axt'd () |(#) | () [(®) |(%) %) (&) (&) |(B) [(B)|(®) [ (%) '(%) (%) Tributyl - phosphate 11 56 4 96.5 |8 17.4|o,7 |0.01 |(0.01 |58 |6.6 |0.07 |0.08 3.5 Dibutyl _ butylprhos- , ' phonate 55 o7 6 99.4 111 64 1.13/0.05 ]0.13 |97 54 _0.72 1.0 18 Butyl . dibutylphos- ' ' ' phinate 98.5 | 99.9 | 15 99.9 |14 o4 (20 (1.9 |7.9 1{9%.4! 98 |23 38 T4 Tributyl phosphine oxlde 99.7°192.9 139 99.9 | 17 99.9|97.3{ 37 64 9989 99.8 12 |77 98.7 & pfter Higgins, Baldwin, and Ruth, veference 387. Experimental conditions: equal phase volumes equllibrated 30 minutes at 25 0.2°C; organiec phase - 0.75 M phosphorus compound dissolved in CCly; aqueous phase - 0.1M uranyl salt with or without salting agent. b Aqueous phase - 0.1M UOp(NO3)p from dissolving irradlated U slugs in HNOg - 6 monthe cooling. £ Aqueous phase - 0.1M Th(Nog)lp 621 £ Extraotiog l Extraction Extraotion of aoclds~ of UQaS0u~- 1 of UOaClo H,80) concen- | HCl concen- % extracted . tration tration ' oM oM oM 1M Aced cit-| Tar- | mNO so, | H,PO, | HEL - — tic | ric ] tarie 3 250 3T U U U U ext'd ext'd ext'd ext'd Tributyl (%) (%) (%) (%) phosphate 0.001 | 0.001 | 0.3 0.8 25 |0 0 7 0 0 0 Dibutyl butylphos- 0.1 0.03 |1 26 phonate Butyl dibutyl- phosphinate 16 48 4o 92 49 |20 |20 27 2 3 0 Tributyl phosphine . oxlde 95 96.82 | 90 all pre- |58 |39 [23 39 {0 10 7 gome ppt. clplitated formed a | | Aqueous phase - 0.1M ansou; acld as indicated. Aqueous phase ~ approximately 1N acld. Three phases wWere present, two of which were largely aqueous. 921 Teble XVIII. Extraction of Actinides and Zlirconlum by Phosphates and Phosphonates at 30°0$ Solvent b o Extractiog Goefficignt o Th Np(IVv)— Pu(IV)= U(VI) Np(VI)& Pu(vIi)d Zr Trilalkyl phosphate= n-butyl 2-3 3.2 16.1 26 15.6 3.5 0.22 lscbutyl 2. 2.7 11.8 22 15.9 3.4 n-amyl 2.9 4,2 15.6 32 19.3 L.l 1go-amyl 4,2 .7 17.8 34 18.9 4.4 0.12 n-hexyl 3.0 3.6 15.6 38 20,0 4.5 0.14 n-octyl 2.4 3.4 15.3 3 15.7 3.9 0.1k 2-ethylhexyl 2.5 4.3 2 5 23 5.7 <14 2-butyl 0.45 4.9 2 o 20 4,6 3-amyl 0.22 3,5 18.1 4o 22 5.0 3-methyl-2-butyl 0.18 3.0 2L hr 25 5.4 4-mathyl-2-amyl 0.047 3.5 22 3 24 h.9 cyclohexyl 3.5 106 0.64 Dlalkyl alkylphosphonate£ dli-n-butyl n-butyl 24 92 O.lI dl=n-butyl cyclohexyl 17 125 0.1 4l -n-amyl n-amyl 3 133 0.092 di-n-hexyl n-hexyl 2 89 0.070& dl-2-ethylhexyl 2-ethyl- hexyl 10.6 176 0.12 & pfter T. H. Siddall III, references 388 and 389. E-Aqueous phase contalned 0.01M ferrous sulfamite. E-Aqueous phase oontalned 0.01§.N3N02. El--Aqueeus phase contalned 0.0lM ceric ammonlum sulfate. g-1-.09M trialkyl phosphate in n-dodecane; extractants washed with 1M NaOH, water, and nitric aold before use; aqueous phase 3.0M HNO3 at equllibrium; tracer concentration of element. I 1.09M phosphonate in n-dodecane;aquecus phase 0.8M HN03 at equllibrium; tracer oconcentration of element. E-Ettrapolated value. extractants may extract uranlum from sulfate and phosphate solutlone, especlally 1f a small amount of nitrate 1s added to the soliutlon. Tributyl phosphate (TBP) Aqueous nitrate systems. Inveatigations on the ex- traetion of metal nitrates by TBP 1ndlcate the catlons are extracted as single, well-defined specles: M(NO3)3(TBP)3, M(NO,), (TBP),, and MOE(N03)2(TBP)2.@21—81ML323- This differs from the extractlon of ethers, esters, and other oxygen-contalning solvents, consldered previously, in which a whole serles of complexes contalning varyling numbers of nitrate, solvate, and water molecurles lg extracted. The atabllity of the TBP-solvate molecules lncreases 1in the orderfill HEO(‘I‘BP) < Pu(N03)3(TBP)3 < Pa.(NO3)5(TBP)3 < HN03(TBP), HNOS(TBP)(HZO) <& Th(N03)4(TBP)2 < PL102(N03)2(TBP)2 < Pu(N03)4(TBP)2 < U02(N03)2(TBP)2. The unexpectedly large extractlon of nitric acld, thoriunh and zirconium at very high acid concentratione indicates higher complexes may be extracted.éll' The dlstribution of uranyl nitrate betweén_TBP end water ig represented in filgure 30.—3'-—9--lk The extraction coefficilent of uranlum 18 plotted as a functlon of acld concentration for varlous concentrations of TBP 1n filgure 31.322 The obsBerved affects of (1) decreased @, with increased acid comncentration and (2) Llncreased a, with increased TBP concentration, may be explalned on the basis of free solvent concentration. Flrst, as the acld concentration 1s increased, more nitrie acld ls extracted resultlng in less free solvent. Second, more free sblvent ls obviously avallable as a result of in- creasing the solvent concentration. Since the partition coefficlent of uranlum depends upon the second power of the free solvent concentratilon, %, wlll decrease in the first case 127 Bzl Table XIX. Extraotive Power of Tributyl Phosphate, Alkyl Fhosphonates, Diphosphonates, and FPhosphine Oxidee.-fi. 0 (cquo)eP‘\‘ 03H7-n 0 Initial concentration of HNOg,N l 0.5 1 2 0.5 1 2 | 0.5 1 2 } 0.5 1 2 Dlstribution goefflclents Solvent U Pu(IV) ILZr-Nb Nb (cuugo)apo 0.68 1.4 3.,65{ 0.19 0.67 2.73| .64 b6 105 .011 .0l .010 (CuH90)2P§H3 4.50 10.35 21.50f 5.46 11,15 14.907 .0058 .0040 .,015 | .0OOL .0020 .017 0 i (1-051{110)2?-01{3 6.95 21.10 70.60| 1.53 T7.43 16.90| .15 .22 .33 .52 .34 .20 * 0 (C6H130)2_P\\-CH3 5.72 18.45 u45.70] 3.51 11.65 18.95| .10 .053 .13 .0050 - 012 .021 N . (CTH150)EPQCH3 21.30 7.1 131 3.25 10.95 17.15| .0078 .04%0 .12 . 0000 .ol 00080 N 0 (cafll.ro)ap\— CH3_ 22.10 50.70 178.0 5.71 13.65 19.45| .037 .14 .28 .0061 019 .ok (09H190)2P90H3 27.60 32.60 61.L0| 23.25 24%.15 21.70| .97 .67 .55 .013 014k 017 Y (0101'[210)2P\\' GH3 6.73 14.65 34.30} 16.60 21.65 21.50| .38 40 54 . O0U3 L0043 .00%0 0 . (c>-c51i110)2?-cn:_l 17.45 44,10 101.0| L4.47 17.35 25.15 .020 .061 .30 .015 013 .00B7 ; 2 0 (CGHSO)EP—CP% 0.08 0.053 0.15| 1.8% 1.34 1.71{1.31 L42 .86 4o .15 .086 % 0 224:9"’;;?-0}13 13.43 28.80 69.90| 3.80 11.60 19.60| .24 .16 .24 | .0056 .0053 0062 67137 N\ 0 ('°4H9°)\1=-cu3 12.20 36.3 65.8 | 7.89 17.85 24.50 | .80 .47 .47 .0038 .0041 .0051 (c'(Hlso)/\\ 0 - - 4.97 13.05 4k.20} 2.58 7.58 14.B5] .031 .091 .33 - - - (n c,\Lfigo)aP%cEH5 0 (1_04[{90)5._03 7.58 22.50 57.30| 2.53 7.67 14.85| .0085 .018 .11 .0021 .0089 ,039 ‘ 2\\ 275 10.435 22.20 T4.70]| 2.58 B.65 16.75)| .0039 .020 .10 |<.00@6 .0028 .0063 621 (1—05H110)2§§- CHy-n 0 (C4H90)2P - G4H9 *% (C4H90)2PQ; C5H11 0 (i'°5H11°)23$' C5H1a (1-CeH,10),p 2 G H. - -1 5711772 Bz 211 0 (1-05}1110)21:\ - CBHJT 0 (GUHBO)E%%; CHaCeHs (04H90)2§;CH200H3 0 (04H90)2{(CH200235 0 (CMHQO)2%4350H2004H9 o (c4H90)2§ifH(0H3)c52§-oc4flg CyH,0),P ~ CH,CH,CO0C (459)2\\0321*20 4 {cyH,0) P - CH, - P(C,H,0) 4“92\052 g% 0 (1-C5H110)23§: CH, - P(OC5H11-1)2 (CyHg) 5PO (1-04H9)3P0 9.40 22.30 8.98 24.00 8.26 25.75 13.65 28.40 7.68 21.10 9.60 11.50 2.45 6,34 1.13 3.09 1.31 3.11 3.15 B.68 2.30 6.35 2.14 5.57 1.73 12.55 1.32 2.98 1880 1360 5.33 7.26 73.80 65.30 103.5 58.40 30.95 85.4 21.10 7.79 8.86 42,20 3%.50 16.46 17.26 9.60 352 7.19 2,02 7.3 14,15 - .013 2.82 9.4 17.50[ .003% .02 2.45 8.91 17.65( .0032 .024 2.50 9.00 15.75 I.012 .036 2,18 7.69 13.05 .011 .031 2.65 B8.92 17.00| .016 .038 0.47 1,91 6.00| .0034% .0084 0.26 1.16 4.24} .029 .075 0.3% 1.50 5.03] .43 u2 0.80 3.26 10.95( .031 .O77 0.15 2.35 6.39] .021 .025 0.79 2.38 6.24 .ot% .12 2.71 6.72 19.24| .23 .28 3.33 8.5 24,70| .41 41 365 299 83,2 !1.00 1.8% B.lp 21.85 22.55 ..61 .55 .099 .097 Jd1 .13 13 .13 .022 .12 .42 .062 .043 .057 .29 A2 2.45 .55 . 0022 <, 001 .0035 011 .0017 »0012 .92 .0029 .0046 .0050 .0031 .0056 .011 .032 .6} 3.95 .0028 .010 022 0024 011 .0011 .0046 -0057 .0060 .0041 .0080 .011 .031 .60 1,40 .0022 .025 .032 074 .0031 .029 .0012 . 0061 .0067 012 .0058 .011 .031 A7 2.15 e After Petrov, et al., reference 390. Organlc 1 e¢/1 Nb 1 =180; c = ayclo. e - 0.5M phosphorus compound in CCl , nitrilo acld as indicated. Temperature, 20° = 1°C, Volume r&tio Initial sgueaus phase - 50 g/1 U, 1 g/1 Pu(IV), 1 o/1 2r + NpP° (organic aqueous), 2. Time of shaking and of settling, 30 minutes. Io = I N s IIIT ¥ v -0 |—I_I'IIII 1 1 1 v It : . . O — o - ] E _ > - - E - i - q [~ - - S d B - 0o - : 0.0| 1 L1 1.1 IIII 1 1 L1l ILII 1 L1l 0.0l 0.1 1.0 10 MOLALITY (aq) Figure 30. The partltion of uranyl nitrate between 100% TBP and water at 25°C. After T. Healy, J. Kennedy, @. Waind, reference 394. and increase 1n the second. The effect of uranium concentratlion on a, is glven also as a funcilon of nltrlec acid concentration in flgure 32.32§ The decreased extrectlion with lncreased uranium concenfiration may agaln be lnterpreted 1ln terms of the seclvent avallable. The partition coefflceclents of other metal nltrates are aleo decreased, ln general, by 1ncréfiaed uranium ccneentration. More efflc¢lent separatlon may there- fore be achleved by lneresased uranium loading of the solvent. For small amounts of uranium, a high uranium concentration may be attalned 1n an organlc phase sultable for handling by 130 000 1T T T T T T T T T - L - 100 = > _ © ™. &_fl b o s °F E - C - w L. - o - .1 S L 83% TBP s 1OF & 39% TBP 3 = - o 9% T8P ] g - ~ ol + - o - 0.1 ~ 0.0l et Ly y g - o1 2 3 4 5 6 7 8 9 01 INITIAL AQUEOUS NITRIC AGID CONCENTRATION, M Figure 31. The extractlon of uranyl nitrate by various concentra- ticng of TBP in kerosene as a functlon of initial aguecus acid concentration. After 7. Sato, reference 395. C(Condilitliona: Organic phase - volume % TBP 1n kercsene as indicated. Aqueocus phase - 5 g. uranyl nitrate per liter, nitrlc acld concentration indicated. Temperature, 200C; Vo/Vg, 1. 131 2y PARTITION COEFFICIENT, '00 . Al | I 1T 11 IIII 1 m 1 1 l.lTll | 1 1 l‘l.'lr. - 0.0l |4 } ] - 0.005 M I i 0.025 M c . 0.05 M S - 0.0l M § - 0.2 M e I0 | o - C & . C 0.3 M . ] - > ] | T 1 - D 05 M o8 T S 1.0 E‘ > '? - 1.0 M S ) . D - 1.5 M . I J o.l ] 1 M | 1 I]J_Il L1 ) IJ_llII i ] 1 1 1 1 0.1 1.0 10 100 INITIAL AQUEOUS NITRIG AGCID CONCENTRATION, M Flgure 32. The effect of 1lnitlal uranium concentration on the extraction of uranyl nltrate by 20 volume per cent TBP in 0014 8B A& function of 1nitial agqueous nltrlc acld concentration. After R. L, Moore, reference 396. Conditlons: Equal volumes of phases shaken in a water bath at 25°C. dilution of the sclvent. Duncan and Holburt321 have measured the distrlbution of uranium,initlally present in 1.2 to 1200 micrograms per liter between 20% TBP in kerosene and nitric acid solution. Although the results were somewhat erratic, 1t was generally shown that the partition coefficlent 18 nearly constant over this range of uranium concentrations. 132 The extractive cepaclty of TBP is affected considerably by the cholce of dlluent. Tanbe3 extracted U(v1), Np(1IV), Np(VI), and Pu(VI) from 5M HNO; aqueous solutions with 0.15M TBP dlssolved 1ln a number of solvents,;including benzene and chloroform. Larger extractlion coefficlents were obtalned for all the elements tested wilth benzene rather than chloroform a8 dlluent. In the case of uranium, the difference in a, wes - greater than ten-fold. Llttle difference 1n extractlve capaclty was observed wlith TBP diluted by benzene or carbon tetrachloride. Simllar results were obtalned by Dizdar, et al.§22 Uranyl nitrate (0,00BBfl) was extracted from 2M nitriec acld solutions by varlous concentratlons of TBP dlluted wlth carbon tetrachloride, xylene, kerosene, hexane, dlbutyl ethef, diethyl ether, and isopropyl ether. The partlition coefficient was found to 1lncrease with lncreaslng TBP concentration to a maxlmum for pure TBP. For carbon tetrachlorlde and xylene the maximum value was already attalned at 40 mole per cent TBP. The other dlluents are listed above 1n the approxlimate order in which they inhiblt the extractlon of uranium by TBP. Differences in a,,for various dlluents, were found to become smailer wlth increased uranium concentration. Bruce§I§~ has found that the extractlion of flsslon products 1ls also affected by the cholce of diluent. The extraction of uranlum by TBP is considerably en- hanced by the presence of salting-out‘agents iln the aqueous phaiaae.!—"g-g:fip-é The resulte of Sato&gé are given 1n Table XX and figure 33. The extractlon of uranlum by TBP decreases wlth increased 1:s-:m.lznsn:'a't:u:c'e.E—QIZE-:Ll Phosphate, sulfate, and fluoride lons reduce the extrac- tion of uranium by TBP from nitrate media.figg Uranium 1s -extraected from ehlorlde solutlon but less efficiently than. from nltrate solution. Slllica causes poor phase separation 133 Table XX. Extraotion of Uranyl Nitrate by TBP Uslng Varioug Niltrate Salting-out Agents.fi Jalting-out agent Percentage extracted OM HNO4 1M HNO, 3M HNO, &M HNO4 (HNO,) 2.96 82.10 95.52 97.10 NH),NOg 70.00 92.30 96.50 97.40 L1NOg 73.05 94.60 97 .50 97.95 NaNO, 72.50 93.00 97.10 97.80 KNOg 65.00 90.50 96.00 97.10 Cu(N03)2 86.02 97 .50 97.70 99.00 Mg(N03)2 84.35 97 .20 97 .50 99.40 Ca(N03)2 82.48 96.60 96.60 97.50 Zn(No3)2 79.75 98.05 98.10 99.40 Al(NO3)3 99.90 99.60 98.20 99.50 Fe(N03)3 99.80 99.50 98.20 98.90 2 After T. Sato, reference 406. Organic phase - 19% TBP in kerosene. Aqueous phase -~ 5 g/1 uranyl nitrate, 1M salting-out agent, initial gcld concentratlion indicated. _ Equal phase volumes shaken together for 30 minutes at 20°C. and the formation of emulslons. Uranlum may be re-extracted from TBP by contact with sodium carbonate sol_ut:l.on.igg Ammonium sulfate, sodium sul- fate, and urea solutlons have been used satisfactorily.fig2 Water or hydrogen peroxlide is Iineffectlve for TBP contalning conslderable nltric acid.flg2 The distribution of nitrile acld between aqueocus solution and 100% TBP i1s demonstrated in figure 34.E1g The. distri- butlon of various metal nitrates bhetween TBP and nitrate 134 % EXTRACTED rarmnim s gemg Erar s ; | L | ! Q ' 2 3 AMQUNT OF NITRATE SALTING-OUT AGENTS, M 80 Flgure 33. Effect of niltrate selting-out agents upon the extraction of uranyl nitrate at 1M inltlal nitrlec acld concentration. After 'T. Sato, reference 406. sonditions: Organlc phass ~ 19% TBP in kerosene. Aqueous phase - 5 g/l uranyl nitrate, 1M HN03, salting- out agent concentratlon lndlcated. Equal phase volumes shalien together for 30 minutes at 20°C, : 135 M TBP PHASE, ACID GONGENTRATION, Io I I T 1T 1il I T 1 1 nm T avi I " T T T i N Symbol Acid t X HF N v HCI o A% /"JO a HNO3 X% ' o~ -_.-'.;':." .0 = c HeS04 . gl / - n / , & v % [ ‘ , - - X 8 # 0.l 7} i J‘l T 0.01 L '—'—L"'“-ll L L 'l.—lllll 1 L L1111 0.0l Q.l 1.0 10 ACID CONCENTRATION, AQUEOUS PHASE, M Figure 34. The distribution of mineral aclds between 1004 TBP and agueous solution at 25°C. After E. Heafbrd and H. A. C. McKay, reference 412. solutions has been extenslvely investigated. The extractilion ooefficients of some actinide elements are plotted agalnst aquéous nitric aold concentration im figures 35 and 36.£l§:£i§ Ishlmor] and Nhkamurafllz have also measured the partition co- efficlents of Hf, Th, Pa, U(VI), Np(IV)(V)(VI), and Pu(IV){VI) at varlous aqueous nitric acld concentrations. Filgure 37 represents the partition coefficlent of several fission pro- ducts as a function of the nitric acid concentration.ti8-%20 136 00 71717 T T T T T T T 3 IO \a v} Y /A s, =z L) o 1.0 - o ] L - 5 ¢ uvn © A Pu(Vi) | = 4 Pu(lV) c 0.1 v Pu (ill) _ = o Np (V1) ] = @ Np(lV) - < 1 o Th(IV) i ¥ 1 0.0l P 11§ 2 3 4 5 6 7 8 9 10 11 12 [HNOa] aq Flgure 35. The partltlon coefflclent of actlnlde nitrates between 19% TBP in kerosene and aqueous solutlon as a function of equilil- brium nitric acid concentration. @U (VI), ONp (VI), mNp (IV), APu (VI) at 20°-23°C,, after K. Alcock, G. F.-Best, E. Hesford, H. A. C. McKay, reference 413. A4APu (IV), VPu (III), at 25°C. or 20-23°C., after G. F. Best, H. A. C. McKay, P. R. Woodgate, ref- erence 414. OTh (IV) at 25°C., after E, Hesford, H. A. C. McKay, D. Scarglll, reference 415, 137 10 =1 | | | | | | T T 1 LA Pu(y) ® Bk{il) S - & Am({ll} g Cf(ill) . . o Cm{in) Es (i) - =z W0 O i A d o QO 2 o = 0. E._ a <, a 0.01 l i | 1 | I l l I I l o | 2 3 4 3 €6 T B8 9 10 1l 12 [HNOg]aq Figure 36. The dlstribution of trivalent ectinides between 100% TBP and aqueous solution as a functlion of equllibrium nitrie acld concentration at 25°C. After G. F. Best, E. Hesford, and H. A. C. McKay, reference 416. The extractlion of rare earths, Y, Zr, Sc¢, Th,and Am by TBP from aqueous nltric acid solutlon has been investigated by Peppard and co-workers.flgi&&gg Jodine 18 extracted. It forms addition compounds wlith carbon-unsaturated compounds in the solvent. The extractlion of lodline is minimlzed by keeping 1t In a2 reduced gtate and by careful selection of TBP diluents.ézg- Rufhenium 1s.also extracted by TBP. Its extractlon may be reduced by lncereased solvent saturation with uranium, by dlgestion in a nitrate solution of very high lonic 138 o0 F—r—T1T—T7T— 717" 71T T~ T T T T T T - © Eu-100% TBP : L v Ce({lll)-100 % TBP - O F © Nb-100% TBP X C X Zr—-199% TBP ) : - _ o Y-I19% TBP B E - . & E ' ___.-'_' s , O 1.0 Ff e ) 8 [~ ) _"' | = g | / / o | : z y . ? ' . . F ' ] = 0.1 =9/~ D4 v*-w---w A3 = My T : o / i i : @ £ - <1 : .. a s . _ 0.0l - ' —: 0-00! |11 b c | 2 3 4 5 6 7 8 9 10 Il 12 [HNO3]ag. Figure 37. The distribution of flsslon product elements between TBP of several concentrations and agqueous solutlon as a functlon of equilibrium nitrlc acld concentratlon. Z2r, after K. Alcock, F. C. Bedford, W. H. Hardwick, and H. A. C. McKay, reference 418. v, Ia, Ce, Eu, after D. Secarglll, K. Alcock, J. M. Fletcher, E. Hesford, and H. A. C. McKay, reference 419. Nb, after C. J. Hardy and D. Scargill, reference 420. Conditions: Tracer, carrlier-free or with less than 1 g/1 of carrler, used 1n all cases, Zr equllibra- tions made at 20-23°C,; Nb,r~206C.; all otherpg at 250C. TBP diluted wlth kerosene. 139 strength, or by treatment with a reducing agent.fizg Suslc and Jelic-—-—3 and Sato— 406 have studled the TBP extraction of metal nitrates that may be used as ssglting-out agents. The order of extraction of 0.1 mg per ml concentratlons of metal from 2N HNO3 solutions by 20% TBR/kefoBene wlth no uranilum present 1s B1 > Co > Cu > Fe > Zn } cda > Pl:l..‘-tgi The partition coefficlient of blamth under such condltlons, wlth equal phase volumes, is about 0.1l. The results of Satoi‘-(-)-§ are listed 1n Table XXT,. The partitlion of uranlum and other metal nitrates be= tween tributyl phofiphate and aqueous solution ls affected greatly by the presence of hydrolysis producte 1n the organilc Table XXI. Extraction of Metal Nitrates by TBP.& Metal nltrate Percentage extracted OM HNOB 1M HN03 L:LN03 - - Na.NOB - - ICN03 - - Cu(NOg), 0.050 0.025 MS(N03)2 - = Ca(N03)2 0.118 0.064 213(1.*503)2 0.005 - Al1(nNO )3 0.004 0.003 Fe(NOB 3 0.010 0.008 & After T. 8Ssto, reference 406. nitric acild concentration indlcated. Organio phase - 19% TBP dlluted in kerosene. Equal phase volmmee shaken together for 30 minutes at 20°C. Aqueocus phase ~ 5 g/l uranyl nitrate and 1M matnl nitrete at initlal phase, eg., mono- and di-butyl phosphates. These products may be elimlnated by washing or bolling the solvent with an alkaline solution. Two procedures for the removal of TBP Impuritles are gilven. Procedure 142}: TBP is purified by boiling with a dilute caustic soda solution. Add 500 ml of 0.4% NaOH solution to 100 ml of impure TBP. Disetlll at atmospheric pressure un- til 200 ml of distlllate have been collected. The remaining TBP is washed repeatedly with water. It may be drled by warming under vaguum. Procedure 235l: TBP 18 stlrred with an equal volume of 6M HCl at 60°C for 12 hours. The separated TBP ie cooled to room temperature and scrubbed wlth two equal-volume portlions of water, three equal volume portions of 5% aqueous sodlum carbonate solutilon, and three equal volume portlons of water. The resultant TBP 1s dried by heating to 30°C under reduced pressure. Aqueous chloride systems. Uranium is extracted from chloride sclution as U02012 « 2TBP although hlgher uranyl chloride complexes may also be em;rza.c‘cet:'i.-E—Q—é-"—'—ltgg The par- tltion of uranium between TBP and aqueous hydrochloric acid solution 18 shown in figures 38%22:%29 4ng 39,230 Mo effect of uranlum concentratlion on the dlstribution 1s given in figure 4O;fl§§ the effect of TBP concentratlon, in figure MI.EEQLEEI In Table XXII, the influence of salting-out agents on the extraction of uranyl chlorlde by 30% TBP in dibutyl ether 1s recorded.fiil The dlstribution of hydro- chlorlec acld between TBP and aqueous solution is shown in figuré 34.513 In figure 37, the partition coefficients of Pa, Th, Zr, and Sc¢ are plotted as funetions of aqueous HCl concentration.flggl&gfi In flgure 39, the partitlon coefflclents of Ni, Mn, Cu, Co, Zn, In, and Fe (IIT) are similarly plotted.330 Ishimorl and Nakamura&ll have measured the partition coeffil- clents of Hf, Th, Pa, U (VI), and Np (IV)(V)(VI) as functions of aqueous acld concentration. Gal and P.uva.m-c-JEil have similarly 141 T riuri ) X o o T ) t— ] & Rl s ok ! C :\? S - DY — 1.0 f - C ; 4 & C ) P - / a -l L_ ; f: IOE . I_I_Llllll IO-E L i 1 2 ro Figure 3B. The extraction coefficient of U, Pa, Th, Zr, and Sc between pre-equilibrated 100% TBP and agqueous hydrochlorlc acid at 220 + 20C. After D. F. Peppard, G. W. Mason, and M. V. Qergel, reference 429, and D. F, Peppard, G. W. Mason, and J. L. Maier, reference 422, : 142 1000 —r——T——T1T——T7T—T—T1T—T 1T 71T 1 7 [ Fe(ll) __g==""" F §ee=mmtSmmTTY 3 100 NG - o C . - ! | - Z wl o 10F 3 W C 7 (1 = - wl L - o _ i o ™ = 5 = 0F 3 —_ - - o - - ] m - - < a - - 0.0l L1 a1 N I || O | 2 3 4 5 6 7 9 I0C Il 2 [Heilgq., M Figure 39. The extractlon coefficients of U, In, Zn, Cu, Co, Fe, and Mn between pre-equilibrated 100% TBP and aqueous HCl solution at 21 + 0.1°C. . After H. Irving and D. N. Edgington, reference 430, TCondltione: TBP and HC1l pre-equllibrated by stirring equal volumes together for about 10 minutes. Tracer concentrations or about 0.02M U and Cu used. Equal volumes of pre-equllbrated phases stirred together about 5 minutes. 143 Iq ] \.l .l e III T l I ¥ T lll 1 L | v ) | 2-initial U _ 100 L concentration . o . @ LN ] L s ' ! N i = “w o - N - w . * . ui . 10 — — 8 [ . \@\ : - l—equilibrium U ™ i Z : N d S - concentration N = - ® 4 = I i |— @ L - o a. (I - [ 1 i 1 1 r_0 lll a1 [ ] 1 3 | ' | lll - 1 i 3 | I ll- 0.0l 0.l 1.0 10 [UO2Cis)aq, M Flgure 40,. The distribution of U0,Cl, between 100% TBP and aqueous HC1 solution as & function of uranium concentration of the aqueous phase. Curve 1 represents the partition with the equilibrium aqueous uranium concentration plotted as absclssa; curve 2, the partltion with 1nitlal agqueous uranium concentratlon as abscissa. . After A. S. Kertes, and M. Halpern, reference 428. Condltlons: Conatant HC1l acid concentration of 8.83M; equal phase volumes eguilibrated for 15 minutes at room temperature, 18° - 22°C. 144. i00 = - < o _ = . Ll o |0 = L [ - L C _ o = O - = b— ez 1.0 q b Q. _ o I 1 1 1 o-I l % TBP Figure 41. Partltlon coefficlent of uranium as a functlon of TBP concentration for various initial aqueous HC1l concentrations. 10.7M, 6.75M, and 1.02M HCl curves, after V, M. Vdovenko, A. A. Lipovskil, and S. A. Nlkitina, reference 426. Conditions: TBP dlsgolved 1n benzene. Extraction made at rcom temperature using U233, 4.6M, 5.9M and T7.6M HCl curves, after V. B. Shevchenko, I. G. Slepchenko, V. S. Sechmidt, and E. A. Nenarokomov, reference 427. Conditions: TBP dlssolved in CClh. Equal phage volumes (10 m1) mixed together for 30 minutes and allowed to stand for 12-15 hours. examined the partition coefficients of Fe (II)(1rIr), U (VvI), ca (11), Sr (II).Zr (IV), Ce (III), Ru (IV),and V (V). Agueous _perchlorate systems. The distribution of uranyl perchlorate between TBP and water at 25°C is shown in figure 42.;§2- Figure 43 gives the partiltlon coeffilclient of uranium as a function of the aqueous perbhloric acid conc:em:r-f.xt_:T.on.lé2 145 Shevcheriko gg_gl,fizg-have studied the extractlon of uranyl perchlorate ln the presence of HClOu, LiClOu, and NaClOu. The saltlng-out capaoity of these salts increases 1n the order listed. The choice of TBP diluen; also affects the extraction of uranyl perchloraté. From.an agqueous solution of 0.065& HC10, and 1M Na0104, the extractlon of uranlum by 2.20M TBP wae found to decorease In the following order of d:I.lue:r:i:s:E-3-g isoamyl acetate > n-butyl acetate > 1socamyl alcohol > toluene > Xylene > benzene > carbon tetrachloride. The distribution of perchloric acld between TBP and aqueous solution is glven in figure 34_fll§ The partition coefflclents of Th, Zn, Pm, Y, and Ce are plotted against aqueous per- chloric acid concentration in figure 44.231 Ishimori and Table XXII. Effect of Saltlng-out Agents on the Extraction of Uranyl Chloride by TBP.2 Salting-out agent . a, - 0.03 NaCl, sat'd 2.85 KCl, sat'd 0.38 NH)C1, 5M 0.71 LiCl, 5M 0.90 HC1l, 5M 17.6 CaClE, 2.5M ' 5.06 Mgcla, 2.5M 11.7 AlClB, 1.6TM 23.8 & After Gal and Ruvarec, reference 431. Initial composition of organic phase - 30% (v/v) TBP 1n dlbutyl ether, sat'd with 1.225M HC1l. Initial compositlion of aqueous phase - 1.225M HC1, 0.1M UO 012, salting-out agent at concentratlion 1ndToat®d. 146 URANIUM GCONGENTRATION, ORGANIC, M 1 IIJII 1 -I - | III 1 1 111 |]I L 1 1 .I L 11 0.001 ; 0.0l 0.1 1.0 10 URANIUM CONGENTRATION, AQUEOUS, M Figure 42. The partition of uranyl perchlorate between 100% TBP and water at 25°C, After E. Hesford and H. A. C. McKay, reference 169. .Nakamuraiiz have studied the extraction of Pa, and Np (IV) (V)‘(VI) by TBP as a function of perchlorate concentration. Aqueous sulfate systems. Sulfate lon 1s normally con- gldered an interferlng ion in the extraction of uranium from aqueous solutlion by TBP. Veereswarara.o,Eii however, found that significant amounts of uranium may be extracted from sulfuric acid solution and that the extraction i1s inecreased as the acid concentration is increased (filgure 45).53& 147 10% ey o o 1 lJIIIII o o PARTITION COEFFICIENT, o Figure 43. The extraction coeffleclent of trace amounts of uranium between 100% TBP and aqueous solution as a funetlon of equilibrium aqueous HC10, concentration. 25°C. After E. Hesford and H. A. C. McKay, reference 169, 148 - . 0% | = s i ] — L i Z E . o 0F 3 TH C - [T - - w L - o L - O = o 1.0 —= = - ] - C ] o - _ 1000 £>1ooo; 2-ethylhexyl >1000 >1000 dlisobutylmethyl : 450 - 2,6,8-trimethylnonyl-4 - 650 1-isobutyl~l4-ethyloctyl - 600 3,9-diethyltridecanol-6 - 550 2 pfter C. A, Blake, Jr., C. F. Baes, Jr., K. B. Brown, C. F. Coleman, J. C. White, reference 302. Aqueous phase: 0.5M SO5~, pH 1, 0.004M U(VI) initially. Organic phase: 0.1M reagent in solvent indloated. Temperature, 25°.; VO/Va, 1. dialkylphosphoric and dialkylphosphinic aclds, @ generally lnereases as the dlelectrlc constant of the solvent increaaes.ggg For monoalkylphosphorlic acids, a reverse trend 1s indicated.39§ The mechanlsm of extraction of uranlum by dlalkylphos- phoric aclds has been studled by various groups.lfigi;ig&igg&&&l At low uranlum concentrations, the extraotion mechanlsm appears to be consistent with the reactlon 2 2 where HDAP represents & dialkylphosphoric acld. However, 1n vost aq + 2(HDAP} org= UO,(DAP) org + 2H" aq, 158 organic solvents, dlalkylphosphoric acids are largely asso- clated as d:I.mers.LLQ@&HQS&E&§ On this basis, the reaection UGt aq + 2(HDAP), 18 = UO,(DAP),(HDAP), org + 2u* (1) is fl.ncli.c:al.tecl.-:-L»-*rig-"-lég The number of dialkylphosphate groups assoclated with the uranyl ion in equation (1) may be accounted for by a chelate structure 12§;§Q§ feRz O /P \ U02+/ 0 OH 2 1™~ o o : 0 At higher uranium concentratlons, lsopiestlc and viscoslty measurements indlcate that polymeric uranyl-dlalkylphogphate chalns are formed.}ég The extraction coeffilclent of uranium by dilbutylphosphoric aclid, HDBP, is given in filgure 49 as a functlon of nitric acid concentrationfigé The shape of the curve has been explalned by Healy and Kennedy 1ln the followlng manner:l§§ The initlal decrease ln o; between 0.1M and 3M HNO45 is expected on the basls of hydrogen ilon rep?acement by UOB+ lon. However, for o, greater than 10 not enough HDBP ls present in the organlc phase to give the monomeric specles UOp (DBP),(HDBP)o demanded by equation (1). In this reglon, the ex- tractlon mechanlem is llkely to be governed by the reactlon x005* aq + (x+1)(HDBR), org = [UO,(DBP),] 2HDBP org + 2xH' aq. (2) E]x The shape of the extraction curve from 3M to 10M HNO=z 15 simllar to that obtained with TBF and ind?categ & change Iin extractlion mechanism. The likely reaction is U0§+ aq + 2NOJ agq + (HDBP), org = UO,(NO),2HDBP org. (3) The decrease 1ln o; above TM HNO3 is probably due to the competing reaction (HDBP)2 org + 2HNO; aq = 2HDBP - HNo3 Orge. (4). It is 1likely that mechanlsms (2) and/or}(3) also ocour to zome extent at high acld concentratlons. 159 The extraction mechanism of dialkylphosphinic aclds 18 expected to be eimilar to that of dlalkylphosphoric aecids. The former are often found as dimers 1n organic solvents and the partition coeffilcient of uranium, @, exhiblte a power dependence on extractant ooncentration at low uranium: levels simllar to that of dialkylphosphoric aclds.=22 Mono- alkylphosphoric and monoalkylphosphonic acilds havelfieen found in larger polymeric aggregatea.figgl&&g" Partition coefficlents for these extractants exhiblt first to second powsr depen- . ‘dencles ofi.extractant conoentration.ggg Interference 0 uranium extraction by anions increases < POP” . Stripping 1is essentiallj the Inverse process of extraction. in the order €10, < Cl™ < SOy Uranium may be stripped from dlalkylphosphoric aelds by con- tact with hydrofluorig sulfuric, phosphorilo,or even hydrochloric aclds., The stripping efflclency 1s generally lncreased wlth increased acid conc:emi'.l?a.t.:l.on.-lfltg Ammonium or sodlum carbonate stripping 1s efficient.fiflg- Szgergigglf In a search for reagents to modify kerosene as the dlluent for dialkylphosphoric aoids,** 1t was dlscovered that neutral organophosphorus compounds provided a synerglstic enhancement of the uranium partitlon coefficient. The en- hancement 1s increased in the following order of neutral reagent: trialkylphosphaté < alkyl dlalkylphosphonate < dialkyl al- kylphosphinate < trlalkylphosphine oxlde. Table XXV lists @, for several synergistic systems.igg‘ The reason for the enhanced partition coeffiocilent, @, has been * Co=-operative action of discrete agencles such that the total effect 1s greater than the sum of the two effects taken 1in- dependently. _ : **Kerosene la modified to prevent separatlon of a dialkylphosphate salt as a separate phase wheh alkaline stripplng is uscu. Long chain alcohols have been used as chemical modifiers. These, however, depress the extractlon coefficlent of uranium and other metals, 160 ay PARTITION COEFFICIENT, — T T T T T T T T T7T - - 100 — . 10 - : 1O ooy L Lt L1 O I 2 3 4 5 6 7T 8 9 10 11 NITRIC ACID NORMALITY Flgure 49. Variation of a, with nitric acid concentratlions for 0.1iM dlbutylphosphorlic aclid In benzene using 20 ml organhic phase, and 50 ml aqueous phase, and an lnitial firanium concentratlion of 0,018M. After T. V. Healy and J. Kennedy, reference 188. explalned on the basls of (1) the additlion of neutral reagent to the uranyl-hialkylphosphate complex through hydrogei. bond- 1ng§9g or of (2) eliminating the need of monomerizing a mole of dimeric extractantflép in the extraction mechanism (see equation (1)). A recent study of the synergistic system, thenoyltrifluoroacetone-neutral organophosphorus compound, indlcates that more lnvestligation 18 nebessary for a more’ 451 precise explanatlon of synerglatlic effects. Much of the work done on synerglstlc systems lnvolving dlalkylphosphoric aclds is summarlzed.in reference 452. 161 Table XXV. Synerglstic Enhancement of Uranium Extraction Coefficient.2 @y : R tic Organophosphorus reagent Conc.,M Aififignt igmgifiiififi.iith 0.1M F2EHPA Di(2-ethylhexyl) phosphoric acid (D2EHPA) 0.1 135 - Phoaphafes trl-n=butyl 0.1 0.0002 k70 tri-2-ethylhexyl 0.1 .0.0002 - 270 Phosphonates di-n-butyl n-butyl 0.1 0.0002 1700 dl-n-amyl n-amyl 0.1 0.0003 2000 di-n-hexyl n-hexyl 0.1 0.0004 2200 dl-2~ethylhexyl 2-ethylhexyl 0.1 0.0002 870 Phosphlnates n-butyl dl-n-butyl 0.1 0.002 3500 n-butyl di-n-hexyl 0.1 0.002 3500 Phosphlne oxldes tri-n-butyl 0.05 - 0.0025 7000 tri-n-octyl 0.1 0.06 3500 tri-2-ethylhexyl 0.1 0.02 650 & After C. A. Blake, Jr., C. F. Baes, Jr., K. B. Brown, C. F. Coleman, J. C. White, reference 302. Aqueous phase: 0.5M sofi pH 1, CLOO#M U(VI) initlally. Organic phase: Reagents in kerosene diluent. Temperature, 25°C.; Vb/v s l. Di(2-ethylhexyl) phosphoric acid (D2EHPA, HDEHP) This reagent may also be known by a less descriptilve name, dioctylphosphate (DOF). D2EHPA 18 reviewed in reference 453. The extractlon of uranium by The effect of acid concentration on the extractlon of uranium by D2EHPA is shown in flgure 50.£§§ The uwranlum extractlon curve for D2EHPA from nitric acid is similar 1in shape, for the few points given, to that for dibutylphosphoric acld given in figure 49, Flgure 5l lllustrates the effect of nltrate ion on the extractlon of uranium by D2EHPA.Efii The presence of a small amount of nitrate in an aqueous sulfate solution 1n- creasesa the extractlon of uranium slgnlflcantly. An Increase in temperature causes a decrease in uranium extraction.flzé 162 100 - | - 10 — - > _ i o C - = - 1 = - - w O - . w w E§ 1.0 — — O - : 2 B ] o - i = 3 i — o i i < o 0.l — — 00N b—L 1 1 11111 0O 1 2 3 4 5 6 7 8 _ 9 10 Il 12 13 14 AGCID NORMALITY Figure 50. Extractlion of uranium by di(2-ethylhexyl) phosphoric acld in kercsene from mineral acid solutlons. After C. A. Blake, K. B. Brown, and C. F. Coleman, reference 453. Conditions: Organic phase - 0.1M D2EHPA 1n kerosene, 2% (w/v) 2-ethylhexanol. Aqueous phase - 1 gU/1 for a2ll acld solutlons except H3PO4 in which cage the U concentratlon was 100 ppm. Agitation time - 2 minutes. Vgp/Vz = 1 for all aclds but HNO3 in which Vo/Vgy = 2. 163 t000 T T T I 1 ' I T 1T 1Tt S—o> L1l @y 100 PARTITION GCOEFFICIENT, o I 1 I 1 ] I 0 | 2 3 4 5 6 7 NITRATE CONGCENTRATION, M Figure 51, The effect of nltrate lon on the extractlon of uranium by dli(2-ethylhexyl) phosphoric acid. Curve 1 - initial pH= 1.5 - 1.85; Qurve 2 - initial pH = 0.5 - 0.75. Conditlions: 0.0lM D2EHPA in kerosene (1.3% 2-ethylhexanol), 1 g U/1 1n agueous phase, Vo/Vy = 2, 2 min, contact time. Curve 3 - 0.5M SO4, pH = 1.2. Conditions: 0.05M D2EHPA in CCly, 1 g U/1 in aqueous phase, Vg/Va = 1, 20 min. contact time. After C. A. Blake, K, B. Brown, and C. F. Coleman, reference 453, The effect of diluent on q is given in Table VI 223 The enhanced extractlon of uranium by D2HPA in synerglstic com- bination with neutral organophosphorus reagents has already been noted (Table XXV).égg The extent %o which other lons are extracted 1s indicated qualitatively 1n Tables XXVII and ]‘CKVIII.EE}£ 164 Table XXVI. Cholce of Diluent wita Di{2-ethylhexyl) Fhosphoric Aéidné Blluent s Kerosene 1235 HeXane 110 Carbon tetrachloride 20 Isopropyl ether 17 Benzene 13 Chlorcform 3 2-Ethylhexanol 0.1 Cctanol-2 (capryl alcohol) 0.08 B aAfter C. A. Blake, K. B. Brown, and C. F. Coleman, reference 453. 0.1M D2EHPA, 0.004M U (VI), 0.5M SO§ ™, pH = 1.1, Vb/v =1, agitation time = 10 min. (wrilst- action shaker) . Dialkylpyrophosphoric aclds Dlalkylpyrophosphoric acids are used ln the recovery of uranium from low-grade phosphate oreg. Much of the work that has been feported in projJect literature has been summarized by Ellis, 222 by Long, Ellls, and Bailespfléé'and by Brown and Golemancigi :The aclds are prepared Jjust prlor to use by gdding alcohol to a slurry of P205 in kercsene wilth stirring and coeling. A concentration of about 0.1 g P205 per ml of kerosene 1s optimum.%55 A 2:1 mole ratio of alecchol: P205 is used to form the dialkylpyrophosphoric acid. A 3:1 mole ratio should glve about equal mole quantities of mono- and di-alkyl orthophosphorlc acidsufiéé The reactlons are com- plex and mixtures of varlous phosphorlc aclds are formed. With pyrophosphorlc acids, uranifim extraction lncreases wlth carbon chaln length from butyl tc cctylnfifii Nonyl and 165 Table XXVII. Extractlon of Metal Ions from Acidic Soluticns with - 0.1M Di(2-ethylhexyl) Phosphoric Acid in Cjclohexane.é Metal Sodium Chloride (1M) Ammonium Sulfate (1M) Sodium Nitrate Ion pH O pH 0.5 pH 1.5 pH 1.5 H I5 5B a1ts3 As+5 Bate _ ] pet2 g3 N N o =1 > e I ' Z "l =z=2 2=+ HH 3 + w 2w 2 W Z "= W = 2 bR 2 2 nE s = 2 = M o= ams j=s = 1 1 1 1 Wg o R BEEREZ2EZ 22022290kl 22229E22w222 1 EEHEEE == v + w H =2 2 =28 60 B3 & =22 HHEREAHR H=zbHBEHHEHERZMH o W O = [} complete extraction, P = partial extraction, N = no extraction, no test was conducted. o After W. J. Ross and J. C. White, reference 454. Agueous phase: 1-2 mg of ion, salt at concentration I1ndicated, PH indlcated. Organic phase: 0.1M D2HPA in cyclohexane. 5 ml portions of each phase shaken together for one hour. 166 Table XXVIII. Extrectlon of Rare Earths from Chlorlde Solutions with Di(2-ethylhexyl) Phosphoric Acld in Cyclohexane.2 Ion pH1.9 pH1.0 pH1.02 pHO.5 pHO5® pHO y*3 La+3 cot3 prt3 Na*3 E | o Sl w BEEEHEREEE oD o] = o = Hd HHEHE®BE A2 2 2 22 H & EHEEHEEHRE~N D2 2 H & EHEBEBHE -2 222 HEEEHDEZ2 2222 2 2 W =2 2 22 E s e = complete extraction, P = partial extractlon, N = no extractilon. After W. J. Ross and J. C. White, reference i454. Aqueous phase' stgndargssoluiéon of 2 mg/ml cet3; 1 mg/ml Pr+3, Nat Ho+3; 0.5 mg/ml 7p+3, 0.2 mg/ml Y+ , La*3, Eu+3 H +3, Er*3; 0.1 mg/ml Yv¥ ; 1 ml of standard solutlon, 1 ml 5M Nacl NaOH or HCl to glve desired pH in 5 ml of solution.- Organlic phase: 5 ml of 0.1lM D2EHPA in oyclohexane extraction ror 1 hour. Without NaCl. decyl glive about the same extractlion as oetyl.EQQ No appre- clable dlfference in extractlng ablllity was observed between pyrophosphorlc acldes pr epared with octanol-l or t'.>c‘c:5!.nol—2.-%§5—é Most of the studlies have been made wlth octylpyrophosphoric acld (OPPA). Pyrophosphoric aclds deterlorate fairly rapidly wlth tlme at room temperature. At elevated temperatures, the rate of deterloration 1s even greater. Contact with mineral acld causes pyrophosaphoric acids to hydrolyze to orthophosphoric acids. The rate of hydrolysls ls slower with basic sblutions.izi 167 Kerosene 1s a satlsfactory dlluent for OPPA.EEE The acld is used in 1-10% concentration. The partitlon coefflclent of uranlum, &, 1s considera- bly higher wlth OPPA than with the corresponding mixture of orthophosphoric aclde, OPA. The partitlon coeffleclent 1s a function of fthe oxidatlon potentlal of the acld. With OPPA, satilsfactory uranium recovery can be made {f the e.m.f. 1s -0.250 volts or greater.fiéé Reduction of the acld increases the extraction of uranium conslderably. At zero to +100 volts.au 1s about twenty tlmes that at =300 to -200 volts.ffizé The extractlon of iron 1s decreased in reduced solution, 1l.e. %pe(11) < %Pe(III)" Uranlum is stripped from the organic solvent by precipl- tatlion as uranous fluoride. | ‘Several papers have recently appeared 1ln open llterature publicatlons concernlng the extrfiction of uranium by pyro- phosphorle acids. Zangenfiéz has shown that OPFA prepared by the alecoholysls of P205 1s a mixture of several components. OPfA prepared in thls manner was found to be more effectlve in the extraction of uranium than pure dloctylphosphoric acld by two orderr of magnlftude. The pure acld was prepared by syn- thesls, starting from POClB; In an effort to determine the uranium specles extracted by OPPA, Grdenic and Korparflég have 1solated the species U(Oct2P207)2. The specles, however, was insoluble in ligroin, the OPPA dlluent. It was soluble 1n ligroin containing OFPPA in a ratio- of one mole of U(IV)-salt and 2 moles of OPPA. This indlcates U(OctEHP207)4 1s the extractable specles. The same formule was obtalned by determlnation of the uranium content 1n a saturated ligroln phase. Habashifiég has Investigated the extraction of uranium and other metals by OPPA from phosphoric acid solutions. Uranium (VI) was found to be more highly extracted than uranium 168 (IV). This is surprising in view of the increased extractlon of uranium from reduced acld solution mentioned previously. Also, cerium (III) was found to extract more resdlly than cerium (IV). The partition coeffilcients of several metal lons are glven for various phosphoric acld concentrations in Tabls XXIX. The partlitlon coeffliclentgdecrease with H3P04 concen- tration for all the metal lons tested except cerium. The extraction coefflclents of both cerium (IV) and (III) pass through maxima in the reglon of 4M H3P04. The partition coefflcient of uranium ls decreased by lncreased initial uranlum concentration. The addltlon of Na3P04 to the soclution gauses a tc increase greatly--apparently by decreasing %the hydrogen lon concentration 1n the aqueous phase. Fluoride 1lon interferes most seriously with the extractlon of uranium by OFPPA. Zangeniég has studled the extraction of uranium (IV) from phosphoric acid by di{2-butyloctyl) pyrophosphate, BOPPA. AMINES AND QUATERNARY AMMONIUM SALTS. A large number of amlnes, quaternary ammonium salts, and other organonltrogen compounds have been 1lnvestigated as posslble extractants of ur.-e.nimn.il'éi:Eéi The physical chemlstry of uranlum extractlon by amines has been studled by Mcwaell, Baes, and Allenflé&zgég and Boi::-emlt—6-2-fl-£[9 Much of the above work has been summarilzed by Coleman, et al.égi More recently, Mooreflz;-has reviewed the extractlion of a large number of elements, lncluding uranium, by amlnes. The reactlons involved 1ln the extraction of uranium by amines have been revlewed by Coleman, EE_élrégi Organic solu- tlons of amines extract aclds from agqueous solution to form alkylammonlum salts R3N org + HX aq < R, NHK org. (5) 3 The amine salt 1n the organlc phase can exchange its lon for another in the aqueous phase 169 Table XXiX. Partitlon Coefficients of Several Metal Ions Between OPPA and H3P01.r.-a'- . Partitlon coerficient Ton® H3POy concentration 2M 4 &M M U(v1) 190 46 - 23 20 U(Iv) 18.6 14,2 13.5 Th{IV) | 24 23 18 13 Fe(III) 18 8 5 Fe(II) | 1 <1 <1 v(Iv)e 2 0.8 0.1 Ce(IV) - 5 8 3 1 Ce(ILII) | T 22 4 2 After F. Habashl, reference 459. 1 i The coefflclents, with the exceptlon of G (1v)s Were determined from flgures which appear in reference 459. |o 0.4 mg metal lon per ml; 24 OPPA in n-hexane; Vo/Va = 0.1. Vb/Va = l. le R NHX org + Y aq = R3NHY org + X aq. (6) The order of preferences for anions in the organic amine solution s C10,” > HO™ > €17 > HS0, > F~. 3% In this anion exchange representatlon, metals are then ex- tracted from aqueous solutionsin which they are present as anlons or anlonlc complexes. For example, U03* ag + 3X” ag & UOXs" aq. (7a) RSNHX org + U02X3'a.q <"-5 RNHUO X3 org + X". (7b) This mechanlism, however, 1ls indistinguishable from one in which a neutral complex 18 extracted. oSt ag + 2% ag = UOLX, ag. (8a) R3NHX org + UO,X, ac = RSNHU02K3 Org. . (*‘Bb_) 170 The factors that influence uranium extractlon have been studlied most extensively for amine-sulfate Es§¢f.'s:’cem1&'>.§9~1£ The effect of amine structure on the extraction of uranium and other metal lone 1s 1llustrated in Table X}C}{.:?-O---li Uranium (IV) 1s efficlently extracted by primary amines. The effi- clency decreases with secondary and tertlary amines. With uranium (VI) there does not seem to be much correlation be= tween a, and amine class. Wlth primary, sscondary, -and ter= tlary laurylamlnes, au(VI)’ under the condltlons given in Table XXX, is < 0.1, 80, and 140, respectively.égfl With primary laurylamine an emulslon 1s formed.égfl The extraction of uranium 1s also affected by carbon chaln branching near the niltrogen atom 1n tertlary amines (Table XXX). Certain n=benzyl-branched-alkyl secondary amlnes have been found to extract uranium extremely well.="" The uranium (VI) partition coefficients of N-benzylheptadecylaminé, N-benzyltetradecyl- amine, N-benzyldodecylamine, and N-(2-naphthylmethyl) dodecyl- amlne, under the ccndltlons outlined in Table XXX, are 2000, 51000, > 1000, ~1000, respectively.3%® The partition coeffi- clent depends upon the amlne-dlluent comblnatlon. The effect of dlluent on Uu(VI) is indlecated in Table XXX.QQ& The partition coefficient, Gu(VI)’ 1s iInfluenced by uranium concentratlon in that 1t changes the amount of free amine sulfate concentration.§9£ In sulfate solution, bisul- fate complexes the amlne more strongly than does sulfate. The uranium partitlon coeffleclent, therefore, decreases wlth in- creaséd-acidity.égi ExXcess agueous su;fate causes a decrease in GU(VI)°§9£ The partitlon coeffliclent 1ls also decreased by increased temperature.ég& Extraction lsotherms 1ndlecate that four to slx amine molecules are assoclated wlth each uranium (VI) 1on.§9£ The number depends upon fhe partlcular amine used. 1th vigoroue shaking, the partition coefficlent, Qs varies approrximately as the flrst power of the free amine 171 2Ll Table XXX, Effect of Amline Structure on the Extractlon of Metal Sulfates.> Metal lon Partition coeffilclent, a Prlmary Amlnes Secondary Amines Tertiary Amines Amlne, Primepe Di(tri- Aming Methyl- Tri-iso- Tris(2- 21F81— JM-EZ deoyl) 8-244 di-n- octylamine ethylhexyl) amine decyl~- amine emne , Ga, Al v(Iv), cr(III), Mn(II), Fesn , _ Co(II), Ni(II), C‘u II 9 Zn <0c1 <0¢01 <0-01 <0-01 <°l°l v(III) yaE 0.1528 Fe(III) 40 0.5 0.1 <0,01 ‘R.E.{III) 20 0,1 <0.01 <0,01 CeEIV} >50 15548 <€0.01 0,01 TL(IV 10Oo 0.2 <0.1 zZr >1000 350 . . 200 a £ f £ £ Th(0,5M 80y) >5000= »>500 >5004- c <0402 u(1v) 3000 S5000548 55%1-5 ai v'{v; o 1000 51000 >1000 >1000 U(vI 40 1 12 20 50 90 0.2 U{v:ti 258 3% 8 108 U(vI 50= 90~ 30 et a After C. F. Coleman, K. B. Brown, J. G. Moore, K. A. Allen, reference 30%4. 1M S04, pH 1, ~1 g metal lon per liter except as noted. Vo/Vy = 1, 0.1M amine in aromatlc hydrocarbon diluent. ELT o 10 I : H 1-(3-ethylpentyl)-lt=ethyloctylamine TN t . J ' oy a4 H trialkylmethylamlne, homologous mixture, 18-24 carbon atoms I EEES | . ! 1 s s ‘¢ ¥ H bis-(l-iaébutyl—3,5—d1methylhexy1) anlne ."H': Y . -:O' .I.... Goefficlents at loadings of ~5 g Vor ~3 g Mo per liter of extractant. Extraction coefficlents of these metals decrcase as thelr concentratlon decreases. Extraction from 0.5M 304 solution. Diluent kerosene instead of aromatlc hydrocarbon. Diluent chloroform instead of aromatic hydrocarbon. sulfate concentration, Ty(vI) " k [M (2 amine) - nM (U (VI}) orgl, where n has a-value between 4 and 6, characteristlic of the amine.2%% With slow equilibration, in which the liquid-liquid interfacial aree 1s strongly limited and interfaclal turbu- lence is prevented, nearly theoretically 1deal resultg have been obtained;fiég i.e., Cuivy) = k [M (& amlne) - nM (U (VI)) orgll. Small amounts of foreign anlons added to sulfate solu- tions hinder the extraction of uranium more than similar amounts of added sulfate. The order of increasing interference is SOu < P04 < Cl LF K N03.§9£ Effectlive separations between uranlum and other metal lons may be made by cholce of amine and/or diluent (Table xxx).figfi Modlficatlon of the diluent with long-chaln alcohols or other modifiers affects the extractlve powers of the organlc solvent phase. A possible syneprgilstic enhancament of au(VI) has been found with 3,9-dlethyltridecyl-6 amine and di(2-ethylhéxyl) phosphorice acid.flég _ The amine extraction of uranium (VI) from aqueous phosphate or fluoride solutions 1s qualitatlvely simllar to that from sulfate solution. Uranium is extracted from relatively low anion concentrations. As the latter concentration i1s 1ln- creased, a, is decreafled.gg& The opposlte 1ls true for chlorlde or niltrate solutions. Uranlum extraction 1s Inecreased as the concentratlon of elther of the latter two anions 1is 1ncreased§9£ Uranilum may be stripped from the aminé,solvent phase by a number of methods. Uranium extracted as the. amlne~sulfate complex may be strlipped by eontacfi wlith a nltrate or chlorilde solutlion. Alkaline strilpping with ao&ium carbonate results In an agqueous uranyl tricarbonate solution. Ammonium or so- dium hydroxlide forms preclpltates that are difficult to handle. A slurry of magneslum oxlde causes uranium to precilpitate 174 as a magnesium polyuranate.§g§ Tri-n-octylamine (TnOA) The partitlon coefficlents obtalned by Keder, EE_EE:EIEJ 373 for the extraction of actlnide metals from niltric acid solutiomsby 10 volume percent TnOA 1n Xxylene are glven in flgure 52. Carswell§§2 has studled the extractlion of uranium and thorlum by 0.2M TnOA 1n toluene, also, from nitrlc acid " solution. Thorium appeers to be more strongly extracted than uranium In the latter system. Uranlum, however, 18 extracted practleoally to the same extent in both systems for acid . con= centrations up to 6M. The extraction of uranium from hydrochlorle acld solu- tions by TnOA in CClu'haa been studled by Blzct and Tremillon&zi The extraction curve aé a functlon of HC1l concentration is gelmilar 1in shepe and magnlitude to that for trlilsococtylamine plotted in figure 53. Allen and co-workersfigi:&gg have made fundamental studles ofi the extractlon of uranlum from sulfate solutlon by TnCA. Extractlon of uranium from acetlc acld solution by TnOA 1n Amsco D=85 gppears to be lntermedlate between extraction from sulfuric and phosphoric acids on one side and hydrochloric and nitrle acids on the other.ig& Triisooctylamine (Ti0A) The results of Mocnreizi for the extractlon of uranlum (VI), thorium, and fission products from hydrochloric acid solution by 5% Ti0A in xylene are presented in figure 53. The extraction of strontium-85 1s negliglble from 2~11M HCl. Americium (III) and curium (III) are not extracted. Elements which are extracted lnclude Fe(III), Co(II), Zn(II), HE(IV), v(Vv), Pa(V), Ccr(vI), Mo(VI), u(Iv), Np(VI,V,IV), and Pu(Vvi,IV) in addition to those shown 1n flgure 53. The extractlon of iron, vanadium; and chromlum may be suppressed by reductlon to & lower oxldatlon state. Ruthenlum remalns In the organlc 175 |03 1 1 1 I I I I 1 1 I I i o i i ] Pu(IVv) T P t - - “F Nouvi s : - " Np(V){a x 10®) ] = i (1] G 10 E' 2 w - [ = =0 J 5 8 - Np(VI) z UvI) Y o 1.0 | o = F Ao YV NG E [ o ‘ 3 ; = - —Pa(V) A S Pu (1) 0.1 - a - —_— Am (Ill) (a x 102) ey oo' ] 1 L ] ] 1 1 1 1 1 1 0 1 2 3 4 5 6 7T 8 9 101 12 HNO3 CONCENTRATION, M Filgure 52. The extractlion of actinlde 1lons by ten volume percerit trli-n-octylamine in xylene from aqueous nitric acld solution. After l; W. E. Keder, J. C. Sheppard, and A. S. Wileon, reference 472 and 2) A. S. Wilson ahd W. E. Keder, reference 473. Conditlons: (1) Ten volume percent TnOA in xylene were stirred with an equal velume of nitric acid of the deslred composi- tion for 3-5 minutee at room temperature (~25°C.). Phases were separated by centrifugation after contactlng. (2) Uranium (IV) data only. Agqueous solutlons were pre- pared at each nitric acld concentration by dilution of a stock solution which was ~1M U(IV), 0.1M H310y, and ~1M Zn(IX). Solutions for extraction experiments were 0.015M U(IV). TnOA was contacted by an equal volume of 12M HNO3 followed by three contacts of one volume each of' the nitric acld concentration used. Equal volumes of agqueous and amine solutlons were contacted at room femperature for 5 minutes. Phases were Beparated by centrifugation. . - - 176 l OOb 10 a - tad _ — O L < L o < w 1.0 = = — _ i < - - i - - E o L - . 0.1 = - _ Z - m b O L & m o . 0.Gi - 0.001 | | | | | | | } | I | o I 2 3 4 5 & 7 8 ¢S 10 1l 12 HCI CONGCENTRATION, M Figure 53. The extraction of U233, Th230, and fissilon prcducte by 5% (w/v) triisccctylamine in xylene as a functlon of HC1l concentration. After F. L. Moore, reference 475. Conditlons: Equal phase volumes extracted for two minutes at room temperature (24°C.). 177 phase when washed with 0.1M HC1l solutlon. Uranlum 1s stripped into the aqueous phase. Excellent extraction (>90%) of macro amounts of uranium (60.4 mg U/ml initial aqueous concentration) can be obtalned from 9M HC1l with 20% TiOA in hexone. Mooreizg has also Iinvestigated the extractlon of uranlum (VI) from acetlic acld solution by TiOA. Extractlons were carried out 1n the same manner as those from hydrochlorilec acid solution (figure 53). Aqueous solutions of varying acetlc acid concentratlon contalning 2 x 104 alpha counts per mlinute per ml of U233 tracer were extracted with equal volumes of 5% {(w/v) T10A In xylene. It wae found that maxi- mum uranium extraction (>90%) is obtained from 0.5M to 1M acetic acld solutions. The additlon of 3%(v/v) butyl cello- solve to the Ti10A-xylene solution lnhilbits foaming during the extractlon process. By lncreasing the T10A concentration, macro amounts of uranium are efflclently extracted. Greater than 95% stripping may be achieved by contactlng the amine- xylene phase wilith an equal volume of 0.5M HNO3, 3M Hgsou, 6M H,50y, 1M NH,HCOg, concentrated NH),OH, or 0.25M HF-~0.25M HNO3 golution. From 0.5M-1M acetilc acld solutilon, ruthenium (11.5%), zirconium (27.9%), and niobium (11.1%) are extracted. Separation 1s made from strontium (alkaline earths), ceslum and europlum (rare earths), plutonium (III) (trivalent actin- ides), thorilum, protactinium, hafnium, tantalum, lron, lead, nickel, cobalt, manganese, chranium (III), aluminum, copper, zinc, blsmuth, tin,and antimony.izl&&zé The selectlvity may be improved 1f the uranium 1s flrst precipitated by hydroxlde, dissolved with 1M acetlc acid, and then extracted as pre- viously described. Iron hydroxlide 1s used to carry trace amounts of uranlum 1in the precipltation step.fizg _ Other amine extractants. A stated at the beglnnlng of this sectlon, many organc- nitrogen compounds have been investlgated as extractants of 178 uranium. A large number of these investlgatione are reported in ORNL reports (eg., ORNL-IQEEEIZ, ORNL-EOQQEZQ). - For further information, one may refer to these reporte, the summariesig&l&él:iéi previously mentloned, or the review by Mqore.fizl- ' Quaternary ammonium Salts. Thé enhanced extraction of uranlium by hexone contalning tetrabutylammonium nitratezg or tetrapropylammonilum n‘.l.tra.1:e§12 has already been noted {see Hexone). Haeffner, Nilsson,and Hultgrenflzg have also used tetrabutylammonlium nitrate to extract uranyl nitrate with chloroform. Quaternary ammonium galte, unllike amlnes, may be used to extract uranium from alkallne carbonate Esolut:tonxa.&-u:-'-i'@-fl-ig9 The Rohin and Haas compound Quatsernary B-104* converted to the carbonate form has been used successfully to extract uranlium from agqueous solutlons having carbonate concentratlons up to one mfi:ula.rafl§9 Amsco G alone or modifled wlth a long-ochaln aloohol, tridecanol, and kerosene modifled with tridecanol have been used asg dlluents. The alechol modifler improves both the phase separatlon tline and the extractlon coefficient.figg The partition coefflclent exhlbits a negative two power dependence on carbonate concentrationigg in accord with the 1:'eazo.c~,’cion§-(-)-2 b= aq 2(R4N)2003 org + U02(CO3)3 aq T__(R4N)4U02(003)3 org + zcog’ aq. (9) The extractilon coeffilcient 1s virtually independent of the blecarbonate concentration wlth the carbonate-blcarbonate total concentration held constant.flég The coefficient is decreased by an lncrease 1n temperature.Eég Uranium may be stripped from the organlc phase by solutions of HC1, HC1-NH,C1, HNOj, and HNO3-NH4NO3.4 8,480 Mitrate solutions * An lsopropanol solution of dilmethyldiodecylammonlum chloride. 179 are more effective than chloride.~lS Sodium hydrozide (2M- 3M) may also be used as a stripping agent.flgg Clifford, gz_ggyfléi report the extractlion of uranium from aqueous carbonate solutions by (1) forming a singly charged anion, Uogxé,with a complexing agent, and (2) ex- tracting this anion into an organlc solvent with a singly charged catlon. Extractlons were obtained with benzoln 2- oxlne, cupferron, hydroxylamine, peroxide, pyrogallol, and 8-quinolinol (oxine). The latter was used for further study. Arquad 2C, R%N(CH3)201, where R 1is about a 16-carbon chain, was found to be the most effective extractant tested. Hexone was found to be the most effective solvent tested. Kerosene gave no extractlon. With oxine as complexlng agent, the extracted specles was ildentified as RuNUoz(Ox)3. The ex- tractlon coefflcient of uranlum was found to lncrease with increased pH; to Increase with lncreased oxine concentration and with increased R4N01 concentration (to an optimum value); to decrease wlth 1ncreased carbonate concentration. An ex=~ tractlion coefflclent, Qs of 10.9 was obtalned by extracting two volumes of an aqueous solution contalning 0.01K UOE(NO3)2, 0.92M Na2CO3, 0.04M NaOH, and 0.02M Arquad 2C with one volume of hexone contalnling 0.lO0OM oxine. DBoth uranium and oxine were removed from the organle phase by etrong acids. S8Sodium bl- carbonate was found the most effliclent strlpplng agent on a counter-current basls. CARBOXYLIC ACIDS. HHk-Bernstromlggl&gg has studled the extraction of uranium (VI), thorium, and lanthanum by several earboxylic aclds: sallcylie, methoxybenzoic, 3,5-dinltrobenzoic, and ¢lnnamie. Table XXXI 1lists the pH at which 50 percent of the metal lons are extracted from perchlorate solutions by 0.1M solutions of the carboxylic acld In hexone. Chloro- form was found to be a poor solvent for the extraction of 180 Table XXXI. pH for 50 Percent Extraction of U(VI), Th, la by Carboxylic Ac1d.2 Acid pH50 U0§+ H Lot salicylic 3.12 3.332 4,935 Methoxybenzoic 3.42 3.82 3,5=Dinitrobenzolic 2.752 2,852 4,385 Cilnnamic 3.60% 3.072 6.13% 2 After B. HBk-Bernstrom, references 138, 482. Aqueous phase: metal concentratilon, 107°M Th or La, 10'3§ U; ionic strength, 0.1M adjusted by the addltion of NaCl0,; pH adjusted with NalH and HC10,,. Organic phase: 0.1M carboxylic acld in hexone. Vb/va’ 1; temperature, 25°C. — Log a = 0, reference 138, [ Calculated from data glven 1n reference 482. the metals by The carboxylic aclds studled. Cole and BJ:'o1.'«m£5‘3-i have atudled the extraction of U(VI), Th, Hf and Zr from agueous nltrate solutlons by sallcyllc acid in furfural. Satisfactory separatlons between uranium and thorilum were obtalned, depending largely upon the two metal concentrations. Sudarikov, gg_éi.flgi have studled the extractlon of U (VI), T™h, Ce, La, ¥, and Sc from aqueous solutions by sali- cylic acld in 1socamyl alcohol. The uranium complex was Qb- gerved to extract at pH 1.5 and to be completely extracted at pH 2.5 to 5.0. Up to pH 6.5, «, was found to decrease from 100 to 0.3=0.4 and to remaln unchanged at higher pH values. Mills and Whetselfigé have extracted uraniuml(VI) with . perfluorobutyrlc acid dissolved in dlethyl ether. 181 CHELATING AGENTS. The chelating agents described below are listed in the same general order as they may be found in the book by Morrison and Freiser,ggg 0 0 Acetylacetone, CH3 - Q - CHé -C - CH3 The extraction of both uranium (VI) and (IV) from per- chlorate solutions with acetylacetone as chelating agent has been investigated by Rydberg. The percentage extracted 1s glven as a function of equilibrium pH in figures 54A,-B, and -C for the three solvents, chloroform, benzene, énd hexone, respectively. The extraectlion of other aotinides, fisslon products, and hafnium 1s also included in the figures.lflh&il' £§§:£§§ Strontium and potassium are poorly extracted by acetylacetone l1nto chloroformmfigl Lanthanum and samarium are poorly extracted by the chelating agent into all three solvents,fléz K:-fl.:slhen&§2 has 1nvestigated the extraction of uranium (VI) wlth acetylacetone used both as chelating agent and solvent. The results are glven in figure 554 together wlth the extractlion ourves of several other metals. The eifect of masking agents, ethylenediaminetetraacetate, fluorilde, and tartrate, on the extractlon of these metals 1s glven in figures 55-B,-C and -D, respectively.figg The extractlon of uranlum by acetylacetone-chloroform 1n the presence of sodium chlorlde and EDTA has been studled by Tabushi.flgg Sodium chloride Increases the eXx- traction yield and broadens the favorable pH range. EDTA permits the separation of uranium from thorium and filssion products by more effectlve masking of the latter. Uranium has also been extracted with acetylacetane using butylacetate as flolvent.-li-s-;--:L 182 100 |- 80 |- HiQv) 4 100a I+a = r 40 | 20 ot L1 1 1 -t O I 2 3 &4 B8 6 7 8 9 101 12 13 14 EQUILIBRIUM pH Figure 54-A. The extractlon of various elemente from 0.1M NaClOy solutlions by an equal volume of acetylacetone-chloroform solution at 25°C. Acetylacetone concsntrations used: TU(VI), 0.0210M [HAa] aq; U(IV), 0.50M [HAa]Y org; Pu(IV), 1.00M [HAa] init; Th(IV), 0.04B9M [HAa] init; Hf'gIV), 0.050M [HA8]O org. After J. Rydberg, references 51, 485-488, 1 T T I 1 I | 1 1 1 1 1 100 |- - 80 I Pu{lv) - U - - 3+ =T 680 | - n a A 40 | - 20 | - 0 1 ] 1 1 ] ] ] ] | 1 -l O 1 2 3 4 5 6 7T 8 9 10 I EQUILIBRIUM pH Figure 54-B. The extraction of various elements from 0.1M NaClOy solutione by an equal volume of acetylacetone-benzene polution at 2500, Acetylacetone concentrations used: U(VI), 0.0210M [HAz]aq; U(Iv), 0.072M [HAa]aqg; Pu(IV), 1.00M [HAa]init; Th(IV), 0.0673M [HAa]éorg; F.P.,0.70M [HAa]QOorg. F.P. irradilation time = cooling time = 1 year. After J. Rydberg, references 51, 487, 488, 492 and J. Rydberg and B. Rydberg, reference 1l4b. 183 I I I [ L L 1 1 { 1 1 T I 100 |- - X Pu(IV) - 80 F ' jé\u(vn ] Oy 8': 60 - - “ a0 | il 20 - : HT(Iv) - o 1 1 L1 1 1 1 1 11 1 -l O1I 2 3 4 58 8 7 8 9 10 1l I2 13 14 EQUILIBRIUM pH Figure 54-C. The extraction of various elements from 0.1M NaCl0y solutions by an equal volume of acetylacetone-hexone polution at 250C. Acetylacetone concentrations used: U(VI), 0.0210M [ HAa]aq; Pu(IV), 1.00M [HAalinit; HF, 0.050M [HAa]Qorg. After J. Rydberg, references 51, 487, 488, 0 0 1 n Benzoylacetone, 9 - C - CHé =C - CH3. -493 Stary has determined the stabllity constants of uranyl acetate, oxslate, tartrate, and EDTA complexes. The effect of these lons was obaserved on the extraction of uranium (VI) from 0.1M NaCl0, solutions by 0.1M benzoylacetone in benzene. . 0 0 o I o n 2-Acetoacetylpyr1dine,'(;, -C - CH2 -C - GH3. The extraction of uranium from a O0.2N NaOH, 0.2N acetic acid solution at pH 5.0 to 6.5 by 0.12% acetoacetylpyridine in butylacetate 1s reported by Hara.figi 3 g Dlbenzoylmethane, ? -C - CH2 -C -0, Uranium (VI) (0.05 - 0.5 mg) is extracted from aqueous solution by a 0.5% solution of dlbenzoylmethane in ethyl ace- 1:.a1:e.—22 In the presence of other cations, the extraction is made more selective by the addition of complexoreIII (EDTA sodlum salt). Excess complexoneis complexed by a 1% Ca(N03)2 184 1 1 I I I 1 1 1 I i I 1 1 1 1 100 | - - o s ’ - w 80 |- - B y’ Pb < I - £ 6ol i * i - 4 40 - - E; —Qriginally in w L i aqueous layer 4 O i 8 . . @ 20 I 7 == = Originally in - L 17 acetylacetatie o A _ l 0 ey V1 o1y o0y 4 5 6 T 8 9 10 Il 12 13 14 EQUILIBRIUM pH Flgure 55-A, The extraction of varlous metals from agueous solutlon by an equal volume of acetylacetone at 259C. Solid lines 1ndicate the metal was origlnally contalned 1n the aqueous phase. The dashed lines 1ndicate the metal was origlnally in the organlc phase. The PH was adJusted to the deslred value b{ gulfuric acld or sodium hy- droxlde. After A. Krishen, reference 489, T 1T 17 T T 1T 17 T T T T T T 100 |- - - -" - ”'—_ o g EDTA 5 ' Metal : EDTA = 1:30 ¢ = 60 0 ~ == Metal : EDTA= 1:10 ] ! cesdoee : H e ! H Metal: EDTA = 115 40 - ’ E ’I Pb — z ! ! 7 w [~ s g s . & 20 ! ! o , — [ U g T eeanen IT o ese csasfomoso 'ql 1 1 1 1 -l O I 2 3 4 5% 6 T B8 9 101 12 13 14 EQUILIBRIUM pH Flgure 55-B. The effect of ethylenediaminetetraacetate (EDTA) on the extractlon of varlous metals from agueous solutlon by an equal volume of acetylacetone at 250C., The mole ratio of metal to EDTA 1s shown by the line texture. After A. Krishen, reference 489, 185 -t 15 1715+~ 175r+°C 7517+ T7TTq7rrTrT 100 |- - L Cu d pey--x ¥ ¥ N X N ) & w ol 27 Po _ - é O 5 . J < # e . - 60 § Fluoride - % 0 ' w I : Motali F~ = 18 ) 8 - am e tF- s ; 40 | 8 mtol. F= o |10 _ w 8 o r ¢ 4 5 8 4 2 0 } ] 1 ] ) ] 1 1 ] 1 L 1 1 ] 1 L -1 O 1 2 3 4 5 6 7T B8 92 101U 12 13 14 EQUILIBRIUM pH Figure 55-C. The effect of fluoride on the extraction of varlous metals from agqueous solution by an equal volume of acetylacetone at 2500, The mole ratio of metal to fluoride 1s shown by the line texture. After A. Krishen, reference 489, T T T T 1 1 1 1 T T 1 T 1 T T 100 | Feo - - o U a [ -L-—---------c“ ) . 02 g = Hf 2 g0 ¢ Pb o :f ¢ Tartrate - ¢ x 60 [ T P T - 1:30 w g Metal: Tartrate : — [ - e = Matal: Tarfrate =1:10 fi 40 | - o [ g Zr 7 [+ 4 L w 20 - a o 1 1 1 1 1 1 1 -1 O 1 2 3 4 B 86 7T 8 © 101 12 13 14 EQUILIBRIUM pH Figure 55-D. The effect of tartrate on the extractlon of varlous metals from aqueous solutlon by an equal volume of acetylacetone at 250C, The mole ratlio of metal to tartrate is shown by the line texture. After A. Krishen, reference 489. 186 gsolution. The resulting solution 1is neutralized wilith ammonia to pH 7 and 1s then contacted several times wilith the extract- ing solutilon. The dibenzoylmethane extraction of uranium with chloroform, benzene, and carbon tetrachloride has been investigated by 7 Moucka and Stary.igé Thenoyltrifluoroacetone (TTA), ’[;]l— C~CH, -C - CF n B 3. 0 0 Considerable effort has been expended in the study of TTA a8 an extractant for uranium. King,&gl Orr,Egg Helslg and Crandall,flgg-Walton, et .'sl.l.,ég9 and Petersonégl-have made fundamental studies on the extraction of uranium (VI) from aqueous perchloratefigz&&gg and niltrat 49 00 medla by TTA dlssolved in benzen 4 498,500,501 hexone,igg cyelo- he:mnone,&22 and pentaether.Egg The partitlon coefficilent, “u(VI)’ is increased by lnereased TTA concentration 1n the organlce phase; decreased by lncreased initial uranium con- centrat:l_on.ég-g The effect of pH and varlous salting agents on the extraction of uranium (VI) and thorium from nitrate solutions by 0.2M TTA 1in benzene 1ls shown 1n filgure 56.29g Salting agents 1lncrease the extractlon of uranlium by TTA- benzene from low pH solutlons. There 18 no apparent effect on the extraction of thorium with or wlthout IE_AI(NO3)3. A 4fl NH4N03 concentration in the aqueous phase (not shown), in fact, depresaes the extractlion of thorium.égg The effect of forelgn anions on the extractlon of U(VI)II and U(I‘U")-5—§ from aqueous perchlorate solutions by O0.5M TTA in benzene 1s shown in filgures 57%&A and 57-B, respectlvely. Poskanzer and li‘o:l:'emz.:.n-s-p-i have recently revliewed the extraction of elements throughout the perlodlc table by TTA. The pHvalues for 50 percent extraction into an equal volume of 0.2M TTA 1n benzene at room temperature or 25°C. listed hy these authors 187 { I 1 T T 100 a 80 il - . & = 860 3 l E 40 L o @ w e 90 0 Flgure 56. The effect of pH and salting-out agents on the extraction of uranium (VI) and thorium by TTA-benzene solutlons. After E. K. Hyde and J. Tolmach, reference 502. Condltlons: An egqual volume of 0.2M TTA in benzene was stirred vigorously for 20 minutes wlth an aqueous solution containing 0.003M thorium or trace amounts of uranlum-233 with or wlthout the esalting-out agent indicated at the pPH gliven. are: for U(VI) from dilute nitric acid,2%2 PHz = 1.97; for U(VI) from HC10, + LiClOu,&gg b =2, Py = 1.79; for U(IV) from HC1O, + Na0104,;£5 k=2, pHgg = -0.58; for U(IV) from HNOg,2%% pH_( = -0.31. 3 Irving and Edg:l.ngtonilél have observed a synerglstlc en- hancement of the uranlum partition coeffilclent with tributyl- phosphate (TBP) - or tributylphosphine oxide (TBPO) - TTA mixtures. The results, a,, versus percent TBP or TBPO 1n the extractant mixture, are given in figure 58. The analysls. of metals with TTA has been reviewed by ‘Moore, 222 Sheperd and Meinke2%® have published, with references, the extraction curves of a large number of elements with TTA. 188 - vy c I 2 3 4 5 6 7T 8 9 1i0 NORMALITY COMPLEXING AGENT Figure 57-A. The effect of forelgn anfons on the extractlon of uranium (VI) from aqueous perchlorate solution by TTA-benzene. After R, A. Day, Jr. and R. M. Powers, reference 77. Condltionas: Organic phage - 0.50M TTA in benzene pre-treated by shaking with dllute per- chloric acld overnight. Aquecus phase - ~10-5M U233, anion at con- centration indlcated, 0.05M HC104, plus sufficient NaClOy to maintain an lonic strength of 2,0. Equal phase volumes shaken together for 2 hours at 25°C, IJ)'% N G- £3 A, . 0 - LN ]E \“ -— a R a ¥ = . F v S _a Figure 57-B. The effect of foreign anilons Ha—SCN -| on the extraction of uranium (IV) from 8 aqueous perchlorate solutlion by TTA-benzene. & After R. A. Day, Jr., R. N. Wilhite, F. D. C.; X — Hamilton, reference 58. Conditlons: Organic o J Phase - 0.05M TTA in benzene pre-treated with 3 - dilute acld. Aquecus phase - 0,0016M - 0.0037M i soZ- J U(IV), anlon at concentration indicafed, 1.000W fi & 'H+ (HC10) used for all experiments except chlo-— 7 ride in which HC1l was used), plus sufficient <% NaClOjy to maintailn an lonlc strength of 2.0. Equal phase volumes shaken together for 30 min- b = utes. '.d. t__;_L___aL___J 0.0i o l 2 3 NORMALITY COMPLEXING AGENT 189 l03 I ——0 Rél I | = ST TTA-TBPO 0 O~ - 7 N L @ 102 |- e > f ; u . - - _ - G s 'OF 3 ™ : : m C - = : Q - - O I . < o LOF 3 = - . e | 1 o L - 0™ |- E |0-2 l I 1 l | ] ] ] l | O 10 20 30 40 50 60 70 80 90 100 % TBP OR TBPO Figure 58. The synergistlic enhancement of the uranium (VI) parti- tlon coefflclent between agqueous nltrate solutions and mixtures of TTA and TBP or TBPO 1n cyclohexane, After H, Irving, D. N. Edging- ton, reference 451. Conditions: Organic phase - 0.02M mixture flf TTA and TBP or TBPO in cyclohexane. Aqueous phase - 1.025 x 10-%M U233, 0.01N HNO3. ual phase volumes shaken together for 24 hours at room tefibera%ureE?21° - 230C.) 190 Substituted l-phenyl-3-methyl-4-acyl-pyrazolones-5, 1 CH3-S-CH-C=O N C=0 e/ &t Skytte Jens.enlé9 has studled the posgibllity of using gsubstltuted l-phenyl-3-methyl-4-acyl-pyrazolones-5 as extrac- tants for a number of elements including uranium (VI), thorium, and lanthanum. The pH for 50% extractlon of trace amounts of these elements by a lfllaolution of chelating agent 1n chlorof form ls given ln Table XXXII. The pH5O-for TTA is glven for comparison. 5 4 " '\ 8—Quinolinol (8-hydroxyquinoline, oxine)’ 7 o 18 A - A OH H Hok,égl and Dyrssen and Dahlberglfii have studied the ex- traction of uranlum (VI) from aqueous perchlorate solutilons by oxine dlssolved in chloroform or hexone. Results of the latter group,lfii percent extracted versus flnal aqueous pH, are shown 1n figure 59. These results are 1n agreement with those of Hok2CL (0.,1M oxine - CHC1, 10'3& U, aqueous per- chlorate solution, ¢ = 0.1M, 25°C.). No apprecisble differ- 4am110_3fl ence was observed with uranium concentrations of 10~ (open and solild circles, respectively, in figure 53). Chloro- form 1s shown to be a sllghtly better solvent for the uranyl- oxlne complex than hexone. The extractlon curves for Th,§g§ La and Smggg are alsc shown In the figure. A tabulation of pH for 50% extractlon of various metal oxinates by chloro- form has been made by Dyrssen and Dahlbergifii and ls repro- duced 1n Table XXXXTIIT. The extraction of uranium (VI) by solutione of 1% oxine in chloroform from huffered aqueous solutions 18 shown in figure 60 as a functlon of agueous pH.élg 191 Table XXXII. pH for 50% Extraction of Tracer Amounts of Uranlum (VI), Thorium, and Lanthanum by 1M Solutions of Substlituted (R) 1-Phenyl-3- methyl-4-acyl-pyrazolones-5 in Chloroform.2 R pfiso.of Metal Ion uos" 't 1e3* acetyl -0.15 0.10 2.60 proplonyl 0.05 0.05 2.65 butyryl 0.52 0.42 2.47 valleryl 0.24 0.24 2.84 capronyl o.7 -0.25 3.15 ethoxycarbonyl 1.00 not meas. 2.50 chloroacetyl 0.65 0.05 2.28 trifluoracetyl 0.8 not meas. not meas. benzoyl _ 1.0 0.4 2.45 p-bromobenzoyl 0.9 0.30 2.3 p~niltrobenzoyl - - - TTA : 0.70 -0.30 3.75 2 vValues for pH50 were calculated from data presented by B. Skytte Jensen, reference 160. | Aqueous perchlorate medla. 192 100 |- - F 3 & ;: fi 80 - U(VII-GHGI, ¢ \ ] Eflu | iy @ g - o|*+ U (V1) —hexong |} -Sm-CHGl3 U(VI)-GHCI o A 3- . 0T 8 . ,4 a - . 40 | —La—-CHCl3 - q A 1 20 § | o l . ol offe L 11 1L 11 -1 O I 2 3 4 5§ 6 7 8 9 10 il 12 13 14 15 EQUILIBRIUM pH Filgure 59, The extraction of tracer amounts of uranium (VI), thorium, samarium, and lanthanum from perchlorate solutlon by solutlions of oxlne-chloroform or oxine-hexone. After D. Dyrssen and V. Dahlberg, reference 1433 D. Dyrssen, references 508 and 509. Conditions: Aque- ous phase - lonic strength = 0.1M with NaOH, HC104, and NaClQy; for uranium, open clrcles represent U.OOOlfl U concentrations, solid clreclea and trilangles, 0.001M U. Organlc phase - oxlne concentrations: for U, 0.100M; for Th, 0.050M; for La and Sm, 0.5M; solvent indicated. Equal phase volumes equllibrated at 25°9C. Substltuted qulnolinols. Rulfs, et 81923 and Dyrssen, et al.2:* have studled the extraction of uranlum by dlhalogen derivatives of 3-quinol- inol. The uranium extraction curves with 1% solutlons of 5,7=-dlchloro- and 5,7~dibromo-8-quinolinol in chloroform are shown as functions of final aqueous pH in figure 60.2lg Use of the halogen-subetltuted oxines permits extraction of uranium from more acldic aqueous solutions. Similar ocurves for uranium, fhorium, and lanthanum are given in figure 61 - for extractlon wlth 0.05M 5,7-dichloro-oxine in chloroformréli Hynekélé-has g8tudled the extractlon of varlous metals by 8-~hydroxyquinaldine (2-methyl-8-quinolincl). The uranium complex was found to be extracted, but notquantitatively, 193 . Table XXXIII. pH for 50% Extraction of Metal Oxlnates wlth Chloroform.2 Metal lon pH Procedure Reference Ga3t 1.0 V ag =V org, 0.1M total oxine. 511 In3* 2.1 Anions in aqueocus solution: chloride, a3t 3.4 Fe3+ 1.6 Four successlve extractlons with 512 cust 2.0 0.01M solution of oxine in CHClafl In3+ 2.2 Anions in aqueous solutlon: sulfate, B13+ 3.0 acetate, nitrate, chlorilde. 3+ Al 4,2 N12+ 6.1 cot 6.5 sn*t 0.0 V ag = 5V org, 0.0TM oxine. 513 Mo 1.0 Anions in aqueous solutlon: Fe3t 2,0 acetate, chloride, tartrate. Cu 2.1 Ni 3.7 Al 3.8 Mot 6.4 by u ' Hf 1.3 V ag = V org, 0.1M total oxine. 143 UO%+ 2.6 Anions in aqueous solution: Th4+ 3.1 perchlorate. sm+ 5.7 La3"' 6.5 2 pfter D. Dyrssen and V. Dahlberg, reference 143. * pH = =log[H'] + 0.1. by chloroform from an aqueous phase at pH 9.5 contalning tartrate and acetate ions. Cyanlde or H202 prevented ex- traction. N=0 1-Nitroso-2-naphthol, "Ny -0H . NN Alimarin and Zoloi-.cwé-:-l'-g have inveatligated the extractlon of uranium (VI) by organiec solutions of l-nitroso-2-naphthol. It was found that a mole ratio of naphthol to U308 of 125 194 10C == @0 | 20 |- 20 - o Loy L1 1 -t Ot 2 3 4 5 6 7 8 © 10 1 12 13 EQU!LIBRIUM pH Filgure 60. The extraction of uranium (VI) by oxine and its 5,7 -dichloro- and 5,7-dibromo~-derivatives. The percent extracted, P, was ‘calculeted from the values of the distributlion coefflclent glven in the paper by C. L. Rulfs, A. K. De, Jr., J. Lakritz, and P. J. Elving, reference 510. Conditlions: 2.1 mg of uranium 1n 10 ml and 25 ml of an spproximately 1M buffer solution were shaken 6 to 8 minutes with 20 ml of 2 1% oxine-chloroform sclution. The aqueous phase was rinsed twice with 5 ml of ahloroform. The pH of the flpal "aqueous phase was measured. 195 100 - _éi;;_ 0 | 40 r 20 - EQUILIBRIUM pH Figure 61. The extraction of tracer amounts of U (VI), Th, and La by 0.05M 5,7-dichloro-oxine dissolved in chloroform from 0.1M HC10, - Na0104 solutions at 25°C. After D. Dyrseen, M. Dyrssen, and E. Johansson, reference 514. and a volume phase ratio of organlo to aqueous of 0.25 1is more than adequate to glve quantitatlive extractlion of uranium into lsoamyl aloohol at a pH of 5 to 6. Two minute shaking is sufficlent for quantitative uranium extraction. Ethyl acetate, n=butanol, dlethyl ether, amyl acetate, benzene, and chloroform also extract the uranium-naphthdlite complex, Quantitative extraction 1s obtalned with ethyl acetate and n- butanol at a pH of 3.0 to 8.5; with isoamyl alcohol at pH 4,5 to 7.5. Quantitative extraction can be achileved at tem- peratures of 0° to 100°C. Chloride or nitrate ions at con- 196 centrations up to 0.2M do not serlously lnterfere with the extraction of uranium. Iron (III) 1s completely extracted; vanadium (IV) and (V) and thorium are partlally extracted. The extractlon of all four metal ions 1s conzlderably suppressed by complexling with complexore ITI (sodium salt of EDTA). The pH range for quantitative separation of u- rmanium with isoamyl alcohol 15 Increased in the pfesence of complexone ITI (~25 mg complexore per mg of metal) to 6.5 = 9. Aluminum and zlnc are not extracted with l-nitroso-2-naphthol. Dyrssen, gg_g;,éll-have studled the extractlion of uranium and thorium from aqueous perchlorate solutions (k = 0.1M) by 0.1M l-nitroso-2-naphthol in chloroform. Fifty percent of the uranlum was extracted at pH 3.07 and fifty percent of .the thorium at pH 1.66. ILanthanum and samarium were not extracted. Other metals that have been extracted as nitroso- naphtholates include Mn(II), Fe(II), Co, Ni, pu(II), Pa(II), Ag, Cd, Hg(II), Pu(IV)2LL ang Np(v).218 Ammonium salt N-nitrosophenylhydroxylamine (cupferron), 70 N - 07, NHf. Cupferron ls an lmportant reagent in the analytical geparation of uranlum. The reagent preclpitates uranium (IV) from acidic (H2804 or HC1l) solution but not uranium (VI). By converting uranium to its two 6x1dat10n states, - geparatlon can be made alternatlvely from elements not pre- cipitated by cupferron and ffom thoée preclpitated by the reagent., The uranium (IV) cupferrate complex, U(Cup)u, was found by Auge::é-]-'2 to be gsoluble 1n chloroform and neufral organlc solvents., Furman, gg_gg,gég found milligram amounts of uranium {IV) to be incompletely extracted from agueous acid solution by hydrogen cupferrate 1ln chloroform but to be almost completely extrscted by ethereal hydrogen cup- 197 ferrate; 1.e., ocupferron extracted by ether from an acld solution. Ethereal hydrogen cupferrate was also found to extract quantltatively macroamounts of urahium {IV) from (1 + 19) sulfuric acid containing hydroxylamlne hydrochloride and submilligram amounts from (1 + 19) sulfuric acid in the | presence of saturated mercury-zinc amalgamegig The partition - coefflcient, qu(IV)’ 18 Inoressed wlth lnereased cupferrate concentration and 18 decreased wlth lncreased acid concen- tration.gég A uranium (VI) cupferrate complex is precipiteted by the reagent from neutral solutibns° There appear to be two forms, one of which 1s soluble in ethyl ether;gfig From (1 + 9) sulfuric aeild, milligram amounts of uranium (VI) are extracted by an equal volume of chloroform with an ex= cess of cupferrdn presentngfig The extraction of urantium (VI) cupferrate from aqueous perchlorate selution by hexone and chloroform is given in figure 62 as a functlon of the pH of the final aqueous solution.lfl; Chloroform 1s a poor solvent for the complex. Hexone 13 better, but quantitative extraction ls not achieved by a single contact of the solvent with an equal volume of the aqueous seolutlon. The extraction curves for Th,égg Sm, and Laégg are also glven 1in the filgure. The propertles of other metal cupferrates have been reviewed by Furman, Mason, and Pekolaogig N-Benzoylphenylhydroxylamine, @- C=0 | Dyrssenégg-has studled the extraction of uranium (v1) ~with N-benzoylphenylhydroxylamine in chlnfioform from aquecus perchlorate solutions. The results, P ?ersus PH, are shown in figure 63 together with those for thorium and lanthanum. 198 ! i 1 I ! P ! I' ¥ g i L L loo _Th-hefione .;:,_:;_'-.-_':._. T T T o] ) B S ) - 80 - B 60 ; T i 1 8 40 ¢ - b ' - [ : 20 - 0 ] 1 1 X . -1 Ol 2 3 4 5 6 7 B8 9 10 Il 12 13 EQUILIBRIUM pH Figure 62. The extraction of tracer amounts of uranium (VI}, thorilum, samarium, and lanthanum cupferrates from perchlorate solu= tlone by hexone or chloroform. After D. Dyrssen and V. Dazhlberg, reference 143; D. Dyrasen, references 508 and 509, Conditions: Aqueous phagse - lonle strength = 0.1M with NaOH, HC10 and NaCl0y. Na cupferrate added to aqueous phase: for 0.01M, for Th, Sm, and La, 0.005M. Equal volumes of aqueous and organlc solvent indlcated equlllbrated at 25°C. y 2 Z N\ 1-(2-Pyridylazo)-2-naphthol (PAN), LI\:P' ~N=N O HO : 1-(2-Pyridylazo)~2-naphthol forms colored complexes (generally red) with a large number of polyvalent metal 1ons.égi The uranyl-PAN complex 13 ineocluble in alcohols, carbon tetrachlorlde, chloroform, and ethers.égg Ortho- 199 vk i 1 f ! ! i i 1 i ' I 100 |- 7 - . 80 7 60 = r ] 40 i - 20 - . ! ] o i 41 01| 2 3 &4 8 6 7 8 © i0 I 12 EQUILIBRIUM pH Figure 63. The extraction of tracer amounts of uranium (VI), thorium, and lanthanum from perchlorate solutions by N-benzoyl- phenylhydroxylamine dlssolved in chloroform. After D. Dyrssen, reference 520. Conditions: Agqueous phase - lonic strength = 0. 1M with HC1Ox, NaOH, and NaClOy. The aqueous phase was sometimes buffered with 1 ml of 0.1M anilinium perchlorate, sodium acetate, or hydrozinium perchlorate per 15 ml. Organic phase - 0, 1M N-benzoylphenylhydroxylamlne in chloroform. Temperature, 25°C. or meta=dlchlorobenzene and bromobenzene are excellent sol- vents for the complex. The maximum color of the uranyl-PAN complex 18 developed at pH 10. At pH less than 5 or greater than 12 little complex formation occurs.égg UOranium may be selectively separated from a large number of elements by PAN-dichlorobenzene extraction in the presence of masking 200 agents (EDTA, trinitrllotriscetlc acld, cyanide) and with proper pH control. 29 Sodium diethyldithiocarbomate (DDTC), (CoHg)N - C Nat. \S" Bode223 reports that the U(VI) - DDTC complex, unlike other heavy metals, 18 soluble 1in water. A precipitate 18 formed only with high concentrations of uranium and reagent. The uranyl-DDTC complex ls practlcally inextractable by carbon tetrachloride but is readlly extracted by isoamyl alcohol, dlethyl ether, and amyl at:e1;.sa.1:e.-5-gi Others have ~used hexone,ég&-ethyl ace't:ate,-igi chloroform,égé and ben- zene'—‘z'-gl to extract the complex. Employlng the above sol- vents, the U(VI)-~DDTC complex has been extracted from aqueous solutlons having a wlde range of pH, e.g., pH 1-5221 and pH 6.5-8.3.225- Sodlum tartrate has been used to prevent hydrolysis at higher pH values.222 The U(VI)-DDTC complex 13 extracted In the presence of EDTA. Uranlum may then be geparated from elements such as thorlum,that form strong EDTA complexes.figfllégz&égg Uranium may be further separated from those elements extracted as DDTC complexes by strlpping the former 1lnto an ammonium carbonate solution.lgélégé. CH=N—CHéCH2-N=CH=- N A~ 0H HO Dyrssen222 reports that uranium (VI) 1s somewhat Digalicylethylenedlimine, extractable (60-90%) with solutions of disalicylethylenc- dllmine 1in chloroform. Hafnlium and thorlum are extracted (90-99%) from weakly acldic solutlons (pH 1.5) with a 0.1- 0.5M chloroform solutlon of the reagent. Lanthanum and samarlum are hot extracted. Antipyrine, CH====T - CH3 I O0=—C N -~ CH ~N 3 | 06H5 201 Roddenlgl has mentloned that chloroform extracts uranyl . complexes with antipyrine. Reaa322 has reported that both uranium {VI) and uranium (IV) are almost completely extracted with antipyrlne-chloroform sdlutions from perchlorate medla. Uranium may be separated from thorlum using the antlpyrine- chloroform system. From an aqueous golution of 20.6 ml containing 5 mmoles of Th(NOB),“ 1 mmole of U02(1503)2 and 48,6 mmoles of HCl, 93-94% of the uranium and only 5% of the thorium was found to extract with 36 mmoles of antipy- rine 1n chloroform. The uranyl-antipyrine complex is soluble in niltrobenzene, but not very soluble 1n hexone. P 7\ Tropolone, 'Q§ s *0 OH The extraction of U(VI) and Th from 0.1M perchlorate solutions by 0.05M tropolone 1n chloroform i1s given as a function of pH in figure 64.23% The pH of 50% extraction for U(VI), Th, and Y under the above condltions 18 approxi- mately 0.9, 1.1, and 4.0, respectively. Iess than 50% lanthanum 1s extracted at pH 6.5¢232 DyrssenEal reports the extraction of a uranium (VI)- beta-lsopropyl tropolone complex with chloroform and hexone. Ton Exchange. A number of articlea are avallable 1n which the behavior of uranium toward lon exchange resins s reviewed and in which reference to much of the litera- ture 1s glven. Hyde,éég Katz and .':'.eaa.bor'g,g-(:!hcu::pin,é;’:g Palei,lgz and Ruznetsov, gg_gg,ggg- have reviewed the lon exchange of a number of the actlinlde elements lIncluding uranlum. Steele and Tavernerlgg have outlined several anlon exchange separatlons of uranium. Clegg and Foleyééé have descrlbed the use of 1lon exchange resins in the pro= cessling of uranium ores. 202 100 80 — 80 40 ~ “ w 20 ~ }- - 0o . 1 1 - 1111 ] L 1 1 -1 O I 2 3 4 5 6 7T 8 9 101 12 13 14 PH Filgure 64. The extraction of trace amounts of uranium (VI) and thorium from 0.1M perchlorate solution by 0.05M tropolone in chloro- form at 25°C. After D. Dyrasen, reference 530. In the followlng paragraphs, the dlstrlbution of uranium (and of other elements) between an ion exchange resln and a particular solutlon ls described in terms of the distribution coefficlents, D and Dv' These are defilned as D = amount Mff[gram dry resin amount M™/m? solution and p = amount M"*/ml resin bed vV amount M™/ml solution The two coefflclents are related by the density of the resln bed, Dv = pD. The coefflclent D 1s referred to as KD_by many authora. 203 EEEEE~§EEE§E§E° Anion exchsnge resins commonly used 1n the radlochemical laboratory are the strong base resins such as Dowex-1l and-2 and Amberlite JRA-410 and IRA-~400. The capaclty of these resins 1a approximately 2.5 mllli- equlvalents per gram of resin. Wealk base reslns are also avallable. However, thelr use is more limlted. These regins have capacltles ranging from about 6 to 10 milli- equlvalents per gram of resin. sSplvey, 95_3;,233 have lnvestlgated varlous factors such as resin capaclty, resin phase volume anion adsorptilon, etc, shat affect the sorption of uranium. Trivisonno232 has made a literature survey of factors that influence the adsorption and elution of uranium by and from strong base anion exchange reslns. These are similar to the factors influencing solvent extraction and include, other than those already mentloned, uranlum concentration, anlon con=- centration, pH, the presence of other metallic lons and forelgn anlons, temperature, resln size, poroslty, cross- linkage, etc. The varlous systems from which uranium may be adsorbed by anlon exchange resine are descrlibed below. The resln may be converted to a particular anionic form by washing wlth an approprlate solution. Chloride systems. Kraus and Nelsonfiz’-é have measured the distribution coefficlents for a number of elements between a strong base anion exchange resin (Dowex~1l, 10% DVB, ~200 mesh) and hydrochlorlc acld sclutlionsa of varylng molarlty. Thelr repults are shown in figure 65. The results of Marcus,§§1 obtained under conditions simllar to those used by Kraus and Nelson,é-aé are glven in figure 66, The concentrations of the various elements used in the study by Marcus were puch that the oxldatlon states could be determined spectro- 204 Go¢ _L e B“I T T 1 T T T o 1 |F ¥ | | 1] e T N0 ADS.||NO ADB] w | ELEMENT i q i gq. AND —] 1L ] It 1L L ; | OXIDATION | NO ADS.~NO ADSORPTION O.i6§ HCl, Np(V) 1s exponentially adsorbed from 3M to 6M HC1l (D increases from 1 to 10), and Np(IV) is simllarly adsorbed from about 6M to 10M HC1 (D increases from about 2 to 400). Prevot, gg_g;,éflg have investigated the adsorption of U, Pu, Th;,; Pe, Ce,and Zr " by anlon exchange resin A300D from hydrochlorilc acld solu- tions ranging in molarity from & to 7. Quantitlies of 7 mg Pu, 6.9 mg U and 5.9 mg Fe per ml of solutlon and 2 grams of resln were used 1ln the determination of D. Thelir results are conslderably different than those shown in flgures 65-67. The dilstribution coefficlents of U(VI), and Fe{III) are lower roughly by an order of magnitude. The dlstrlibution coefflcient of Pu(IV) 1s almost an order of magnitude higher. For Pu(III), D 1s about 0.1 at 4M HC1l and about 1 at 7TM HCl. Zirconium adsorptlon 1s simllar to that shown In the figures. Thopium and cerlum are poorly or not at all adsorbed. Korkisch, et al.2+222*2 ngve found the distribution coefficlent of uranium between Dowex-1l and hydrochlorilc acld sBolutions to lncrease wlth lncreased alcohol concentration . *» of the solution. With 80% ethanol, D 18 i1ncreased from about 40 to 6000 as the HC1l concentration is increased from 0.2M to E.EEyQEl The dilstribution coefficient at 2.4M HC1l without aleochol is about 40. Alecohol also lnoreases the adsorption of thorlum, titanlum, and zirconium. The distribution co- * 95% alcohol denatured with benzene 18 consldered 100% alcohol. 207 103 D g Ty < L 9 |02 S — Mo (1) _ [T s 3 m fl ; 0 - S \ o] Lt / = ' / i o . ,’ Zr(IE) = l = ’ IS 10 = i ’( - @ - 2 ] -— - z ~ o - 2 4 5 f / : o o | 1.0 -é |0-| I 1 I -} I ] 8 10 12 14 HC! CONCENTRATION, M Figure 67. Adsorption of elements from hydrochlorlec acid solutlon with Dowex-2 anlon exchange resin (x8, 200-400 mesh). After L. Wish, reference 538. 208 efficlents of these elements vary roughly between 1 and 10 from 80% alcohol solutions contalning HC1l in the range of 0.2M to 2.4M.2%2 Numerous peparations of uranlum from other elements are poselble using hydrochloric acld systems. The more ob- vious ones are those 1in which uranium 1s adsorbed and the other element is not. Conslderatlon of figure 65, indicates that uranium can be separated from alkali metals, alkallne earths, aluminum, yttrium, rare earths, actinium, and thorium by adsorption as uranium (VI) on a strong base anlon ex- change resin from a concentrated hydrochloric acid solution. Trilvalent actinide elements are not adsorbed from hydro- chloric acld sclutions. Plutonlum 18 eluted as Pu (III) with 12M HC1l eontalining hydroxylamine hydrochlorlde and NH4I, NHuI alone, or HI. Separatlons may be made by adsorption of the contamlnating element and elution of uranlium with dilute hydrochloric acld. For exsample, molybdenum 18 adsorbed ffom 0..1;Il;!I_HCl.,§Ei Bismuth is also adsorbed from dilute (<1M) HCl.éE&Lé&é Other elemente that show strong adsorption from dilute HC1l include many of the transition metals, tin, tellurlium, and polonium.éié Kraus and Mooreiité have effected the separation of protastinlum and uranium by adsorblng them from 8M HC1 on a column of Dowex A-1 reein and developing _the column with 3.8M HCl. Protactinium appeared first in the eluent, separated from uranium. The uranlum fractlon contalned; however, a falr amount of protactinium 'tailing'} Advantage may be taken of the different distribution coefficients exhiblted by lons 1ln varlous oxidatlon states to effect thelr separatlon from uranlum. Iron reduced to ferrous lon by hydrogen 1odide§£1 or ascorblc a.c:Lc:lEl—-|~§ 1s separated by elution with 4M HCl. U(IV) may be separated from Pa(IV) and Th(IV). U(IV) 18 adsorbed by Amberlite IRA-401 (100 mesh) and Dowex-1 (100-200 mesh) from >8M HCI. 209 Nelther Pa(IV) nor Th(IV) 1s adsorbed from 6M - 12.6M ne1.249 The elutlon of Pu(III) by 12M HC1l from strong base anion exchange resln has already been mentloned. Wish and Rowelléég have effected the separation of Th, Pu, Zr, and Np from U by elutlon with hydrochloric acld in a sequence of concen- trations. The elements are adsorbed on the resin (Dowex-2) from 12M HCl. Thorium does not adsorb. Plutonlum 1s eluted in the trivalent atate wlth 12M HCl saturated with hydroxyl- amine hydrochlorlde and ammonium lodide. Zirconium is eluted with 7.5M HC1; neptunium (IV) with a 6M HCl - 5% NH,OH - HC1 solution. Uranium 1s flnally eluted with O0.1N HC1. Korkisch, gg_g;,fiél have separated uranium from tung- sten by means of anlon exchange. The uranium is adsorbed on Dowex <1 resin from a solution containing 20% 4M HCI and 80% ethanol (volume %#). Ascorbic acid is used to reduce any 1iron present. The resin 1s washed with a similar solu- tion and uranium 1s elufed wilth an ether-saturated 0.1M HCl solution. No tungsten 1s observed in the final eluate. Fluoride systems. 'F'a.::':T.sé-lig has reported the adsorptlion of elements from hydrofluoric acld solutions wlth Dowex-1 anlon exchange resin (x10, 200 mesh). His resulte are shown in figure 68. Uranlum (VI) adsorption 1s strong from dilute HF solutions and decreases with lnoreased acld concentratlon. Separation from elements exhiblting no or strong adsorptlon from HF solutions may be achleved by.proper salectlon of the aold concentration. Elements such as Be, B, Se¢, Ti, Zr, Mo, 8Sn, Te, Hf, Ta, W, Re, and Hg have adsorptién curves slmllar in shape to that of uranium (VI). Separation from these elements using an HF system should prove difflicult to almost Impossible, dependling upon the distribution coefficlents 1n- volved. 210 NO ADS. — NO ADSORPTION FROM IM-2&8M HF SL ADS. - SLIGHT AD3SORPTION 9TR. ADS.—~ STRONG ADBORPTION: LOG DIST. COEFF. >2 LOG DISTR. COEFF. o u O 10 MOLARITE"\)" HF ROMAN NUMERALS REFER TO OXIDIZATION STATE ] IN INITIAL SOLUTION. NGO ADS.[INO 112 Flgure 68. Adsorption of elements from hydrofluoric acid solutlon with Dowex-1 anilon exchange resin (x10, 200 mesh). After J. P. Farls, reference 552, Bhat and Gokh.s,leénr'23 have found evlidence for the ad- sorption of the anionic apecles U02F3 with Amberllte IRA-300. . HC1-HF szs;ems. Certaln elements are effilclently separated from uranlium by anlon exchange when a comblned HCl-HF eluting system 1s used. Such systems have been studied by a number of work- ers.éég-&éél—*:222 The results of Nelson, Rush, and Krausgég- are shown 1n figure 69. Faris and Brody522 have examined the distribution coeffleclent D of uranlum as a function of HC1 concentration in the presence of O, 1, and 8M HF and as. a functlon of HF concentration in the presence of O and 0.2M HCl. The former three curves are plmlilar 1n shape but decrease in megnltude as the HF concentration 1s increased. The pre- sence of 0.2M HC1l also ocauses a decrease 1n magnitude of the D ve.[HF] curve. However, the shapes of the O and 0.2M HC1l ourves for varylng HF concentration are dlssimllar for HF concentrations less than 4M. ~ Table XXXIV lists a number of separations of U from other elements uslng HCl-HF elutiné golutions. Nitrate systems. The distribution of uranium between anlon exchange resins and nitric acld solutlons has been reported by a number of workers.-53élfiflg&fi&fi&fiég&éfi!&éfig:éég The results of Buchanan and Fa:r-:i.fi';égg are glven in figure 70. From the non=- or only slight adsorption of most of the elements from nitric acid media, 1t appears that anlon exchange affords an excellent means for purlfying uranium. Uranium 1s adsorbed more strongly from nitrate salt solutions than from nitric aecld solutilona alone.égé&éfizlfigg&éé; Wlth DeAcldlte FF resln, the adsorption of uranium (VI) 1s greatest from Al(N03)3 solutions and de- creases 1ln the order Ga(Nq92.> LiNO3 > NH4N03.§§§ Et?anol Increases the dlstribution of uranium to the resin ph;se.éii With an 80% alcoholle solution, the dilstribution coefficient 212 Table XXXIV. Separation of Uranlum from Various Elements by Anion Exchange Using HC1l-HF Eluting Solutions.2& & Dowex-l or -2 anion exchange resin used. 213 Elemental mixture Element eluted Eluting solution Reference W, U W TM HC1-1M HF 555 U 0.1M HC1 U, W, Mo U 0.5M HC1 555 W 7TM HC1-1M HF Mo 1M HC1 W, Nb, Ti, V, Zr, U, Ta W, T1, V, Zr TM HC1-4M HF 559 Nb TM HC1-0.2M HF U 1M HC1-4M HF Ta 24M HF or 4M NH)Cl- 1M NH,F Fe(III), U Fe(IIT) 1M HF-0.01M HC1 555 U 1M HC1 R.E. as Eu(III),u(Iv), R.E. 8M HC1 556 u(vI), Zn(I1I) u(Iv) 8M HC1-0.1M HF u(vI) 0.5M HC1 Zn(II) 0.01M HC1 Te(IV), U(VI) U(VvI) 3M HC1-1M(to 8M)HF 559 Te(IV) 1M HC1 Th(IV), Pa(V), U(VI) Th(IV) 10M HC1 556 Pa(V) OM HCl-1M HF u(vI) 0.1M HC1 Pa, U 9M HC1 551 Pa TM HC1-0.11M HF U 0.5M HC1 ‘Zr, Np, Nb, U, Mo, Tec Zr 12M HG1-0.06M HF 538 ' Np 6.5M HC1-0.004M HF 'Nb 6.0M HC1-0.06M HF alr dry column and alcohol wash U 0.1M HC1-0.06M HF Mo, Te 12M HNO4 ¥ie Ba ]~ " Dy<1 in HCL S [ IE L Dyl _ [ In HGI—] ad | a HEI- I M HF ] Dy= 50 g-g } w = o w 7 w 20 - _ w £ O o ° o S - & = n o o ] - 5 - - S = - o o i £ s @ ’r 1 o - Q o l 1 l n i b 1 | O 0.l 0.2 O 0.l 0.2 SULFATE CONCENTRATICN, ¥ ACETATE CONCENTRATION, N 1 I!IJII DISTRIBUTION COEFFICIENT, D ro I | 1 t O 1 28 3 4 B HpGCgOs CONCENTRATION, % Figure 76. The adsorption of uranium by Dowex-50 cation exchange resln from solutlons of sodium sulfate; sodlum acetate, and oxallec acld, After T. Ishimori and H. Okuno, reference 568. Conditlonsa: Sulfate - 0.5 g resin, NaR form; 5.4 mg U/25 ml; NapoSOy- NaNO3 mixed solution, {Nal = 0.30N. - Acetate -~ 0.5 g resin, NaR form; 5.4 mg U/25 ml; NaOAc- NaNO3 mixed solution, [Nal = 0.16N. Oxallec acid - 0.5 g resin, HR form; 10.8 mg U/25 ml. 226 uranium (VI) on Amberlite IR-120 catlion exchange resin with hydrochloric, nltric, sulfurle, acetle, cltric, and perchloric acids. Uranlum (1.7 mg) adsorbed on a resin bed (1.4 x 14.5 em) was eluted with 200 ml of various eluante. Uranium was quantltatively recovered with 2-4M HC1l, 2-4M HN03, and 1-2M Hasoq. Uranlum was incompletely recovered with 1M HCl, 1M HNO5, 2M HC10,, 2M acetic acld, and 2-5% citric acld. " Sullivan, et al1.22% have investigated the distribution of uranium between Dowex-50 lon exchange resin and perchloric acld medla as a functlon of tlme and blsulfate lon concentration. Table XXXVI 11sts a number of separations of uranium from various elements that have been achleved by catlon exchange. 4, Chromatosraggxw The subJeot of paper and cellulose chromatography for the separatlon of uranlum has been reviewed by Rn:)dden:-L-gg and 198 by Steele and Taverner.—=— Work of Soviet sclentlstas in the fleld heaa been reviewed by Palei-121 and by Seny&wln..élg References to much of the literature may be found 1n the review article by Kuznetsov, Savvin, and Mikha.ilov.ggg Books by Pollardglé-and by Blasiuséli include chromatographlc separations of uranium. One of the most successful separations of uranium by filter- paper chromatography makes use of the solvent, 2-methyltetrahydro- furan.éli Of thirty-one metals tested, only ruthenium and rho- 106 106 dlum, measured as Ru™~ - Rh™ -, and tungsten (W185) were in- completely separated from uranlium (U233). The results for tin (Snll3) and antimony (E’:blzj1L ) were 1nconclusive and the behavior of mercury (H3203) was 8imllar to that of uranium. An example of the use of celluloge columns in comblnation wlth organilc solvent for the separatlon of uranlium is that given by Burstall and Wealls.élé An ethereal solution contalnlng 5 per cent v/v of nitric acld i1s used to extract uranium from a cellulose column. The nitrates of the alkall metals, alkallne earths, rare earths, Cu, Ag, Zn, Cd, Al, In, T1, Ti, Hf, Ge, Sn, Y, 227 BZZ Table XXXVT. Elemental mixture u, b U U U s & g & & G - - Qc dad g d O F.P.{(Cs,8r,Y,Ce) F.P., Pu F.P. La Eu Ce, Eu, Y R.E. R.E. Fe, Cu, 04, N1, Mn Element eluted <+ eluting agent U-1.TOM HOl; Th-1.1M (NH4)2003 U, Th-90% acetone, 5% HCl, H,0 (U eluted first) U=-1M HC1; Th-3M H,SO, U-dil. HC1l; Th-complexing agent (Hso;) U-2M HC1; 0.5M H,C,0, dilute HNO, U=dil. HC1l; Np(IV)-complexing agent gasorb from 1M HNO3; eluted Np ahead of U with 2M HN03 Sr-0.1M HC1; Ce,Y=1M HC1; U-6M HC1l; Cs=5M NH),C1 adgord from uranyl nltrate sclutlon at pH 1-3; 0-0.2 €0 0.3M HoS0y; F.P.-phosphoric aeld and 1M HNO5; Pui-0.8H H3E04 and 1M HNO F.P.=3% Ne,EDTA ; U=-3% NaOAc, 0.25M Na2003 La-0.06% Na EDTA, pH 4.0; U-3% NaOAs, 0.25M Na.2003 U-0.75M H,80,; Eu-6M HC1 U-1M H,C,0;; Ce, Eu, Y-5N HCl R.E.~Na, EDTA U-2, 5M HF U, Fe,Cu-0.5N HpCoOh; Cd,N1,Co,Mn-3N HC1; R.E.-5% ammonium cltrate Separation of Uranium from Various Elemente by Catlon Exohange. Resln Amberllte IR-120 KUo-2 Amberlite IR-120 Reference 592 588 589 phenol formaldehyde 593 type Wofatit KS Amberlite IR-100 alginliq acld Wofatlt KS Amberlite IR-120 Amberlite IR=120 594 595 596 597 597 zirconium phosphate 598 sulfonated phenol formzldehyde type godliunm dialkyl phosphate sodium dialkyl phosphate Dowex-50 Amberlite IR-120 Amberlite IRC=50 Dowex-50 Amberlite IR-120 599 660 600 601,602 603 604 605 606 6272 U, FegIII), Co(II), Cu(II U,Fe(III) U, Co, Cu, Ca U, Ccd U,Th,Ac,B1,Ra,Pb U, many lons U, many lons U, Zr, CegIII),Cu, Ni, Hg(II U, phosphate Fe,Co,Cu~2% Na EDTA, pH 3.0; U-3% NaOAe, 0.25M NaECO U,Fe-0.8M HC1 (U eluted first) adsorb from O.1M HNO3; Co, Cu, Ca=0.2M HNO4; U-resin removed from~column and washed wit 0.25M Na.2003 Cd-0.5N HC1 U,Th,Ac,Bl-5% HyC,0y forelgn lons-EDTA (Na salt)%. PH 7 U-H,S0, forel U-3N H,50, Zr as anlonic oxalate complex anionic EDTA complexes, Hg(II ions-EDTA (Na salt;, (a)p. L1.T-1.9 or (b} pH 5.5=7.0 following Fe(OH.)3 precipitation; Ce(III), Cu, Ni as as anionle lodlde complex are not adsorbed; U-4M HC1 phosphate (NaEHPou) not adsorbed; U-4M HC1 F.P. [=] fisslon products. R.E. [=] rare earth elements. EDTA [=] ethylenediaminetetraacetic acid. godlum dlalkyl phosphate Lewatlt 3100 dlalkyl- phosphoric acld Dowex=-50 KUu-2 Amberlite IRC-50 (a)KU-2 or (b) Amberlite IRC=50 Amberlite TR-120 Amberlite IR-120 600 607 600 608 609 - 610 611 589 589 Pb, Nb, Ta, Cr, W, Te, Mn, Fe, Co, and N1 remaln statlonary or move only sllghtly. Gold reduced with_FeSOu 18 retalned by the column. Mercury (II), selenlum, arsenic, antimony, and bilasmuth move less rapidiy through the column than uranium. Cerlc nltrate 1s extracted as are thorlum, zirconium, and scandium nitrates. Cerium in the III-state 1s not extracted. Thorlum extractlon ip sensiltlive to the acld concentration. Zirconlum extractlon 1s inhibited by phosphate, sulfate, ocxalate, and tartrate lons. Scandium extraction 1s also inhlblted by tartrate lon. Tin 1s precipltated as meta=-stannlic acld. Large amounts of tin may be first removed by volatlllzation as the lodlde. Vanadlum 1ls re= talned 1f peroxldes are absent. Ferrous sulfate reduces vana- dium to an lmmoblle sglt. Phosphoric acld is extracted. Ferrilc nitrate 1lnhlbits the extractlon of this acld. The behavior of molybdenum ie complex. Irldlum and rhodlum are not extracted. Traces of ruthenium and platinum may be found in the eluent. Palladlum 1s extracted. Reduction of platinum and palladium with FeSOu results 1In retention of bulk amounts by the column. Small amounts of sulfate do net lnterfere with the extraction of uranium. Sulfuric acld is retalned by the column under normal conditions. Halldes increase the extractlon of other elements, €.g2.,Au, Sn. Under normal conditlons, HC1l 1s retalned 1n the columm; HBr, HI, bromine and lodine move slowly down the column. Molybdenum and arsenlc may be adsorbed by the use of activated alumina 1ln conjunctlon with celluloseoélz The use of sllica gel columns comblned wilth organle solvents, dibutyl carbltol and trlbutyl phosphates and nltric acid have been used for the separation of uranlum and plu‘l:on:[um.él-a-&élg A non-lonic phosphorylated resin, dlethyl polystyrene- methylenephosphonate, may be used to separate uranium (VI) from 1ron {III), ianthanum, zirconium, niobium, thorium,and mixed fission pr-c>dut3tfl.-§--2-g Uranium is adsorbed by the resin from 2 per cent solutlons of dilbutyl phosphorlc acld. The other elements 230 are not absorbed. Uranium 1ls eluted with a dimethyl formamide= benzene solution. The feasibility of using tributyl phosphate gels for the separation of uranium from iron (IXI) and thorlum has recently been demonstrated.égl 5. Volatilizatlon. Uranium may be separated from many elements by fractional distlllatlon of the volatile compound, uranium hexa- fluoride. This method of separation has been applied to the recovery of uranium from lrradiated fuel elements. Katz and Rabinowitzl have reviewed many of the early methods for the pre- paratlon of UF6: fluorination of various uranlium compounds with elemental fluorlne or cobalt trifluoride, dlsproportionation of UF5 whlch results in both UFu and UF6, and the reaoction between UF, and dry oxygen which results in U02F2 and UF6. The latter two methods are not very practical from an analytlcal standpolint. Other fluorlnating agentas that form UF6 Include ceric fluorlde, manganic fluoride, silver difluoride, halogen fluorides (e.g., BrF., and ClF3) and fused metallle fluorides. Moat elements 3 form fluorides under the condltlons that UF6 1s obtalned. How- ever, ohly a small number of these fluorides are volatile. Hyman, gfi_g&,g have published a table of some 26 elements having fluorides with boiling or sublimation points of 550°C or less. Included in thls group are the fluorides of boron, sllicon, phosphorus, vanadium, sulfur, tungsten, bismuth, plutonlum, and the fission products, germanium, arsenlc; selenium, niobium, molybdenum, ruthenium, antimony, tellurium, and iodine. The bolling point ofIUFs is 54.6°C. Non-volatile fluorides from which uranium is readlly separated Include those of the alkali metals, alkaline earths, rare earths, Fe, Co, N1, Ag, Al, B¢, Mn, T1, Pb, 2n, Cu, Hg, Cd, and ZP.QE;QEE Uranium does not form a volatlle compound by interactlon wlth anhydrous hydrogen fiuoride. Materlals such as Nb, Ta, As, 231 Sb, 51, Te, Se, eotc. do.éi The oxides of titanlum, tungsten, and molybdenum regct slowly wlth HF. Vé05 and VN also react elowly. VO, VéOu and V203 are not vola.til:_l.zed.ii Rodden and \«ha.r-f-;i desoribe a procedure that makes use of both anhydrous hydrogen fluoride and fluorine In the peparatlon of uranilum. Posslble contamlnants of the separated UF6 include Cr, Ta, W, Mo, or V. Uranium hexachloride and uranium (IV) borohydfiide_are volatlle compounds for which procedures might be developed for the separatlon of uranium. Uranium may be separated from arsenlc, antimony, bismuth, selenlum, and tin by volatilization of the latter elements with a mixture of hydrobromlec acld and ‘DJ:'omine.l-2§ 6. Electrochemlecal methods. The electrolysle of dilute sulfuric acild solutioné with a mercury cathode results 1n the quantitative deposition of Cr, Fg, Co, N1, Cu, Zn, Ga, Ge, Mo, Rh, P4, Ag, C4, In, Sn, Re, Ir, Pt, Au, Hg, and T1 in the cathode.213 Arsenic, selenium, tellurium, osmlum, and lead are quantitatively separated from the electrolyte, but are not quantitatively reposited in the catl'acrder.-?-li Manganese, ruthenium, and antimony are incom- pletely separated.glg- Uranium and the remalnlng actinlde elements, rare earth elements, the alkall and alkaline eerth metals, alunminum, vanadium, zirconium, niobium, ete. remaln in solu- tionfgig- Cas’.f:.oég-i and Rodden and Warfléi have reviewed the effects of many variables in the electrolytic separatlon of the above~ named elements from uranium. According to Rodden and Wa.r'f‘,.-afl optlmm condltlionas for the purificatlon of uranium 1n sulffiric acld solutlons wlth a mercury cathode are: electrolyte volume, 50 ml; free sulfuric acld ooncentratlon, 1N; current density, as high as practicable with the given acid concentration (about 10 amp maxlmum); anode, flat platinum spiral or grid just making contact wlth the surface of the electrolyte; cathode ares, 232 a8 large as practlcable; stirring, surface of the mercury cathode 18 stirred rather rapldly; temperature of electrolyte, between 25° and 40°C; mercury for the cathode, pure; anlons, chloride, nitrate, and phosphate i1ons should be absent, or present in only small amounts. Uranium may be deposlted electrolytically at the cathode of a cell from aeetate,ég&ié;l czau.J:'bona.te,-éég--oxa.ls.q.te,gi::-@ig formate,éig-phosphate,éfig fluoride,éfig&éfll and chlo::-:l.de-s-j—{'g solutions. Many of the uranlum electrodeposltlon procedures have been developed 1m an effort to prepare thin, uniform fllms for alpha and fission counting rather than to separate the ele- ment from any particular impurity. However, in the work of Smith and cv:>-‘wor']rcel"E}é-g-l--‘L-"-égg and Coomanségl'uranium was separated from alkall and alkaline earth metals and zlnc. Ga.s.tt;ég-3 and Rodden and ‘.r\Ta.]:'f.‘-Z‘--ll review much of the material pertlnent to the electrodeposition of uranium. Electrodialyslis has achleved & certain amount of lmportance in the recovery of uranlium from leach llquors. In a review ar- ticle by Kunin,éfi; the followlng cells are preegented for con- glderation: (-) cathode anlon permeable membrane anode {+) (1) U0, (No4) 5 NH,,NO4 NH4N03 (-) cathode anion permeable membrane anode (+) (2) U0,S0y, H,S0, H,y80, (-) cathode anion permeable membrane anode (+) (3) U0,Cl, NaC1l NaCl H,yS50) 233 (-) cathode | anlon membrane| NaCl Ication membrane| anode (+) (4) U04C1, H,80, NaCl - oS0y (=) cathode cation permeable membrane anode (+) (5) 2+ Uo,™, Ney €0 Na,CO4 NaHCO, In acid systems (oells 1, 2, 3, and &), the transport of sulfate, nitrate, and chloride ions to the anode results 1ln a removal of acid and a subsequent increase in pH in the cathode compartment. The uranium, reduced during electrolysis, 1s precipitated as U0, or U(HP04)2o In the alkallne system, the transport of so- 2 dium lons 1s also accompanled by a rise in pH in the cathode compartment and uranlum is again preclpltated as the dloxide or as a mixture of dloxide and sodlum polyuranate. The electrodlalytic separatlon of uranium from metals 1n a complex mlxture has been demonstrated by Willard and F:Lnley.gfli An ammonium blearbonate solution contalning U, Fe, N1, Cu, Cr, Zn, Al, Mo, Mg, and Na salts, and traoces of other elements was electrolyzed in a two-compartment cell having a catlon permeable membrane and a mercury cathode. The solutlon was firset made the catholyte (electrolyte in the cathode compartment) and elec- trolyzed. Iron (80%), nickel and copper (95%8), tin, and zinec were removed from solution by deposition. The blcarhonate solu= tion was then made the anolyte and electrolyzed at a platinum anode. All aluminum, molybdenum, ammonium, and sllicon, and some sodium and megnesium were separated from the uranium by migra- tlon. Uranium was retalned as the carbonate complex and was recovered as the oxlde by evaporation of the anolyte. Other features of the slectrodialytic behavior of uranium that may be useful in 1ts separation and purification are (1) the retention of uranium during electrodialysis from & perchloric 234 catholyte ueing an anion selective membrane, (2) the dissolution and separation of impure UF,, and (3) the feasibllity of .electro- dlalysis 1n organic solutions. ot T. Pyrometallu;sicalAprocgsses. Although pyrometallurglical or high temperature processes have been designed primarily for large scale recovery of fertlle material from irradiated fuel elements, some of the methods may find épplication In the radlochemistry laboratory. Types of pyrometallurgleasl operations that have received considerable attention are(l) distillation,(Z.) salt extraction, (3.) molten metal extraction,(d ) oxidative slagging, (5 ) electro~refining, and(6 ) decomposition of uranium iodide. These methods have been revlewed by L&l.'.»n:-oe.]rc'.'l.og-:l-'l l. Plutonium 18 concentrated by vacuum distillation from molten uranium at 1500-1800°C. 2. Plutonlum la extracted from molten uranlum by salts such as UF, or MgCl,. Uranium remalns in the metallic gtate. Plfltonium 15 recovered as a hallde salt. 3. Plutonium ls extracted by molten metals, such as gllver or magneslium, that are immlscible with molten uranium. Fleslon products are also extracted. 4. Oxldative slagging involves the preferential formation of the most stable oxldes by a molten irradiated fuel element 1n a limlted oxygen environment. These oxldes (rare earths) float to the surface of the molten ma=- terlal and are skimmed off. Other oxldes diffuse 1into the crucible and through the slag layer. 5. In electro-refining, uranlum is dissolved anodically 1n a fused salt bath of alkzll or alkaline earth halides that contaln a uranium compound. Noble metals do not dlssolve and are deposlted as anode sludge. Uranium and chemically similar materials are deposited at the cathode. Alkall, alkallne earth, and rare earth fission products concentrate ln the salt bath.. 6. Uranium 1is recovered as the metal from the thermal de- composition of UIA. Zirconlum and nlobium are the principal contamlnants. " It 18 not the purpose of this sectlon to describe the techniques involved in pyrometallurglcal processes. The lnterested reader may consult The many papers presented in "Progress in Nuclear Energy, Serles IITI, Process Chemistry,” volumes 1(1956) and 2(1958), and in the "Proceedings of the International Con- 235 ference on Peaceful Uses of Atomic Energy,” volumes 9(1956) and 17(1958). IV=E Determlnation of Urarilum The amount of uranium 1n a sample may be determined by atandard methods of analysls: gravimetric, volumetrie, colori- metrie, spectrophotometric, e*l:c-,.31LL191"19_5’197’198'200'6)'&5 .Because of 1ts natural radiocactlivity, uranlum may also be deterw= mined by counting technlques. The appllcablility, ln terms of mass range, of varlous methods for the determination of uranium 1s glven in Table XxxvIr.222 1. Counting techniques. Principles of alpha, beta, and gamma counting are considered 1ln review articles by Steinberg,éig Hanna,éiz Deutach and Kofold-Hansen,éflg Crouthamel,éi& and J'a.i‘i‘e:r.g59 All three methods of countlng are appllcable to the radiometric determination of uranium since both alpha- and beta-emitting i1sotopes exist (Section IIX). Spontaneous fissilon half=11ves have been determined for several uranium isotopes: U232, U234, U235, U236, 0238. These 1sotopes are too long-lived, however, to make fisslon counting a practlcal method for thelr determlination. | Ionization chambers are most commonly used for the detection of alpha particles. In figures 77 and 78 are shown the alpha spectra of U235 and U233, respectlively. The spectra were obtalned with a parallel plate, Frilsch grid ionlzation chamber using P-10 (90% argon, 10% methane) gas. A multl-channel analyzer was used ln conJunction with the lonization chamber. Both U235 and U233 samples were prepared by volatilizatlon. Filgure 79 represents the U233 alpha spectrum obtained with a surfacse barfier slllcon s8olid state detector. Data for this flgure was taken from the same sample as that for figure 78. It 1s readily apparent from the.two figures that the solld state detector glves much better resolution of the alpha groups than does the lonlzatlion chamber. 236 Table XXXVII. Range of Application of Various Methods for the Determination of Ur'a.nium.-E Method Ran?e of applicatlon Range of error mlcrograms) %per cent) Neutron actlvatlon 10')+ - 104 2 to 5 Fluoroscopy 1077 -2 ' +5 to 50 Emission spectroscopy 5 X 1072 - 50 +]1 to 10 Visual chromatography -1 o on paper 10 = 10 Volumetric (1lncluding 5 microvolumetric) methods 1-5x10 0.5 to 5 Autoradlography (o emiselon) L counting of tracks l1-10 +1 to 10 Colorlimetry N dibenzoylmethane 10 - 10 +1 to 3 thlogyanate 50 - 5 x 104 tl to 3 H,0, - HC10, 103 - 107 1 to 5 Alphe counting = 50 - 5 x 103 +1 to 10 Polarography 102 - 104 2 to 5 Potentiometry 2 x 10° - 10" +1 to 5 Gravlimetric methods 5 x 101L - 0.1 to 2 a — Adapted from a table glven by A. Simenauer, reference 199, b 50 pg of U238 gives about 20 cpm at 52%4 geometry. Uranlum- 238 may be detected 1n samples having much lower counting rates than thls, dependlng upon the physlcal condition of the sample and the presence of extraneous alpha activlity. For a thin gource wlth low alpha backggggnd, 1 alpha cpm of uranium should be readily detected. For U this 1s the equlvalent cf about 2 ug; for other uranium leotopes, the masa 18 even less. The data for flgure 79, however, was taken 1in 1000 minutes. The. data for flgure 78 was taken in 10 minutes. Alpha partlcles may be counted also by gaseous, llquld, plastic, and crystalline scintlllation detectore. The resolu- tion of these detectors is, 1ln general, less than lonlzation chambers and their applicatlon more limited. Nuclear emilsions are used to record alpha activity. Such devices as c¢loud chambers are generally not used in the radloehemistry laboratory. Geiger-Mfiller counters, proportlonal counters, and liquid, _plastlc, and crystalline scintillation detectors are sultable . for the counting of B -emitting lsotopes, U237, U23% and U240. 237 Iolooo rrTrrirrryrvyrrnrnvial rrritrrrrrrirrrinril r: I { >} ] F @ ¥ i 2 1 py ¢ 0 < . 1000 2 — - = $ B - b " m . -t o - g N o1 ¢ - w - D l ': . - L Y- P > | R - > - § ! 5 2 ) ! - Z [ £ I [3 = - ., = g I g - g O o ¢ . 3 < < fal 2 100 — o g i = P - - F ™~ § a C '&.’5 S ™ 8 : o s f o ) oD ‘_.-':- (\l: i '.' U235 71 x108 ye. | 10 Ionization Chamber o - Detector | _ | Div. = 28.6 kev ] - ‘ |_0 L4y ety vl vt ENERGY —— Plgure 77- Alpha spectrum of a volatilized source of U235 obtalned with a parallel plate, Frisch grid lonizatlon chamber using 90% argon - 1l0% methane gas. D. J. Henderfion, Argonne National Laboratory, Unpublished data. 238 Q000 - M T T T T T I T T T T T T T T T T T T T T T T TT T T T T —_—t 1 11 111 1000 - 0 _ W i 5 ] < i = o = 100 _ 9 - < ) » . = _ 2 : o o~ --'; -1 © 233 5 '- 1 U233 162 x 109 yr. 10 - Ionization Chamber o\ 3 :. Detector D - = | Div. = 20.0 kev ] 3 1 l.oII_LI_LI_L]_I_IJ_ll_lIIIIIJllll_IlIIIIJIJ_I ENERGY —= Figure 78. Alpha sapectrum of a volatillzed source of U233 obtalned wlth a parallel plate, Frisch grid lonization chamber using 90% argon - 104 methane gas'. D. J. Henderson, Argonne Natlonal Laboratory, Unpubllshed data. 239 Ioo;Ooo_[IIII.IIIITIIIIIIIlIIIIIIIIIIIIIIII - i i ¥y © % _ n 24 I | © b - . E.. 7 1\ < _ 10,000 |- = 4| & | : L y o> 3 { . v [~ t A g ‘ - _ i~ g - |_|-l_-| n fl: m - D ~ i z - | ~ | = : T ] i o 2 | 3 — 1000 o 3 - " E - o - * u 0 . wn - © i - - < - 2 o i i o o 100 ‘ 3 U233 1.62 x 109 yr. - o o . Solid Stote Detector - S | Div. = 7.8 kev e o |o iyttt ek ENERGY — Figure 79. Alpha spectrum of a volatilized source of U233 obtalned wilth a surface barrier silicon detector. P. W. Engelkemelir, Argonne National Laboratory, Unpublished data. 240 Sodium lodlde-thallium actlvated cryatals have galned wlde- spread acceptance as detectors of gamma radiatlion. The gamna- ray spectra of U239, U237, U235, U233, dand a uranium are from the Belgilan Congo are illustrated 1n figures 80-8B4%,. The speotra were measured by Crouthamel, Gatrousils, and Goalov:'f.ch-—s-—lt2 wilth a Y-inch dlameter x 4-inch thick oylindrical NaI(Tl) crystal. Not only can the amount of uranium in a sample be determined directly by measuring the dlsintegratlon rates of the various 1sotopes, 1t can also be measured indirectly by determining the activity of daughter products. For such a measurement to be meaningful, however, the equllibrium conditlon between the uranium lsotope and 1ts daughter must be known. Information on the radicactive decay of the uranium isotopes 1le glven ln Section III. Further information on these isotopes and thelr daughter products may be obtalned by consultlng the "Table of.Iaotopes" complled by Stromminger, Hollander, and Seaborgéél and the references given therein. Volumes 8 (1956), 3 (1958), and 28 (1958) of the "Proceedings of the Internatilonal Conference on the Peaceful Uses of Atomlc Energy"” contaln a number of articles on the radlometrlc determinatlon of uranium. Reference to many more articles 1s made in the revliew papers by Meinkenéég 2. Sanple preparatlon. One of the most lmportant problems to overcome 1n the detection of alpha partlcles and 1n direct fisslon counting 18 the preparation of thin folls or sample | depoelite. Thls subject has recelved conslderable attention and hag been reviewed by several authors.63?’647'650’653’654 Several techniques are avallable. The simplest and most quanti- tatlive 1s the direct evaporation of an aliquot of a sample. The dietribution of such deposlts are generally not very uniform. Thie may be improved upon by the addltlon of a spreadlng agent such as tetraethyleneglycol, TEG. Palntling technlques may be uged to bulld up falrly uniform depcsits of several mllligrems 241 RELATIVE COUNTING RATE per square centimeter.éééi-éEg Uranyl nitrate le dlssolved ln alcohol and added to a dilute solution of Zapon in Zapon thinner or cellulose In emyl acetate. This solutlon 1s painted over a metal backing, allowed to dry, and then baked or ignited at a sultable témperature. For aluminum backing, temperfitures of 550° to 600°C are satisfactory. For platinum, higher tempera- tures (800°C) are preferresd. The.thickness of the uranium deposlt 1B increased by repeatedly palnting and baking the foll. 100 U239 23.5 min. 0 No auternat absorbar Geomstry = 48% i Dlv.» 2,95 tev 60 TO 60 g 3 50 = a x 2 s S 40 c 3 3 8 z © 30 3 g ~ 20 10 0 ENERGY — Figure 80. Gamma-ray spectrum of U239 obtalned with a 4-inch dlameter x Y-inch thick eylindrical NaI(Tl) crystal. After C. E. Crouthamel, C. Gauvrousis, S. J. Goslovich, reference 649. 242 £ve RELATIVE COUNTING RATE 100 T T T T T T T T T I T T T T T T T T T T} T T T T T T T TV T T I T T T T 7T 90 fl u%37 g 7 da. 80 1 No axtarnal absorbsr fl Geometry I0% 70 [l‘ Ifi I Div,= B.0 hgv R o g 3 8 ~ - . J 1 } j l T Uy | : . o\ o™ 20 g 8 RV ERYE A ° ' Hk,dfr o *2 g ‘flm;\Huff Tyt v et iy i i i it e s i s i gyt 4 g it g gttty ENERGQY e Figure 81. Gamma-ray spectrum of U237 obtained with a 4-inch diameter x 4-~inch thilck eylindrical NaI(Tl) crystal. After C. E. Crouthamel, C. Gatrousis, S. J. Goslowvich, reference 649, ¥¥e RELATIVE COUNTING RATE 100 [TTT T T I TTTTTTITI T FTI T T T T T T T I T T T T rTrer T T rrITTI T I T T 90 |— UE‘-'35 7.Ix|0°yt. T No external absorber 80 Go?metry 10% | Div. = 6.6 kev 4 counted 30min, after 0 saparotion from - n daughters, 10mgs. U 60 ° < = - 234 x 2 o v .07 % isotopic 50 & _c:: = Ut3%93.41% content z of 9 ues8 559 40 n == |z a __J‘,': - = > 30 M a 3 3 2 2 2 > = o > E ~ ® ® ll] o o > - » < o a 20 12 o n—®a - o - mn o o N /\ © 0 = j Lnd. \_f/ x64 o ] | Lyt v e g et gt Pi 4t 1 bt ENERGY — Flgure 82. QGamma-ray spectrum of U232 obtained with a 4-inch diameter x UY-inch thick cylindrical NaI(Tl) crystal. reference 649, After C. E. Crouthamel, C. Gatrousls, S. J. Goslovich, S¥¢ RELATIVE COUNTING RATE i0o0 T TI T I T T T I it r i rTyTr T T T T T T T T T T T T T T T T i T T T T I T T T I T iTTrrd 80 " w U233 | 62 x10%yr. 80 3 :g:::tcm! Sr(NOz), gtry 10% a I Div. = 6.4 kev 70 3 —— : 2 Mass Anolysis o 7.4 ppm 236 €0 S < | ppm 236 E PI. < | ppm 235 50 a < 2ppm 234 x jl[ < | ppm 232 alz 2 40 —z+Inl=—= | (¥ S A 3 n — Q@ > - : » 3 J‘: £ o |13 o g g 3 _’ l’; gg °—‘ o N,/l\n 20 s -+ : 10 n8 o x 32 o|||| Lid i e et e e e i ettty s ENERGY —= Figure 83. Gamma-ray spectrum of U233 obtalned wilth a 4-inch diameter x 4-inch thick cylindrical NaI(Tl) crystal. reference 649. After C. E. Crouthamel, C. Gatrousls, S. J. Gaslovich, loo I I T I | I I I ' ' I ‘ 1 P10 1 1 1 1 I | ! ]/ | I - a o Uranium Ore J & a {Belgium Congo-hand picke 20 < g < 580 mg/cm® Ba wa 2 |& o t 80 2l é 2 | Dlv. = 78.5 hev O 3 a = ~0 . mm 0 ] E ~ w oo P_; 2 - E g o A5 o« n . ™ ’ 2 © Sep|le v & z : i T s & z (|3 4 3 50 —4 1 0 £ @ .o v g < l.‘-? !—— w )1 "Lk 3 e > 40 T, {i—A 2 . : ~ < z + ™ } : = ng = o 20 §—3 l W K a i 10 } % o |||4111||||1||||l|||||¢|_\L<\'f3=4,.u ENERGY — Figure 8. Gamma-ray spectrum of uranium ore from the Belglan Congo obtalned with a 4~inch ditameter x 4=inch thick cylindrical NeI(Tl) crystal. After C. E. Grouthhmel, C. Gatrousis, 8. J. Goslovich, referenocs 649, Samples of the metastable 0235 l1somer have been prepared by electrostatically collectlng the recoll atoms of Pu239 in air.m A negative potentlzal of several hundred volts was applled to the metalllc collectlion plate. Carswell and Hilstedgég have succeeded in preparing thin sources by a spraying technique. The materlal to be deposited 1s dissolved as the nitrate in an organic solvent (alcohol or acetone). The solutlon 1s drawn into a fine glass caplllary 246 tube and sprayed onto the backing material by applylng an electric fileld. Electrodeposltion 1ls a generally satlsfactory method for preparing uniform samples wlth quantitative or nearly quantita- tive ylelds. Uranium has been plated from a varlety of solu- tionse: acetate,lu.LM formate’s_Bg_ Oxalate,62316'§§'638 carbonate,éfiiéég fluoride,62 632,61 and chlopide_éflg A satig= factory electrolyte for the deposition of uranium is 0.4M gmmonium o:\::aLlaau.i:e.é--s-i A rotating platinum anode 18 used to stir the solutlion placed 1n a vertical cylindrical cell. The cell is made of glass, luclte, or scme other chemically inert material. The cathode on whlech the uranium 1s to be depaslted is thoroughly cleansed and made the bottom of the cell. The assembled cell i1s placed 1n a hot water bath and the temperature kept at about 80°C. A current denslty of approximately 0.1 a.mp/cm2 18 used. The deposition 1s influenced strongly by the rate of stirring, current denslty, and presence of forelgn ions.ftfit Vacuum sublimation preovides an excellent means for the preparation of thin depoelts of uranium. The sublimation of uranlum acetylacetonate, U(05H702)4, has been used. A more convenlent method 1s the sublimation of uranlum oxldes. A uranium salt solutlon 1ls placed on a tungsten or tantalum ribbon supported between two electrodes. The solution 18 dried by a heat lamp or by passling a low current through the metal ribbon. The sample backling materlal is suspended at a sultable helght above the metal ribbon. A bell Jar 1s placed over the assembled unit and evacuated. The uranlum 1z volatlilized by increasing the current through the matal ribbon. The unlformity of the deposlt depends upon the dlstance between the rilbbon and the backling plate. The collection efficlency also depends upon thls distance but in an inverse manner to that of deposit uni- formity. Usually a compromlse is made between collection d efflclency and sample uniformity. Much of the uranium that 1s 247 not collected on the sample plate can be recovered from maskling pPlates and glass chimneys placed between the filament and backing fiaterial. The collection efflclency may also be improved by subliming from furnaces so that the beam of uranium molecules 158 directed toward the backing plate. . The furnace 1s heated lby'electron.bombardment or induction heating. 3. Activation Analysls. In activatiop-analysis, a nuclide irradlated by neutrons, gamma raye, or charged particles 1s transformed infto a radloactlve nucllde more easlly detected than the origlnal one. The amount of orlginal materlal may be deter= mined elther absolutely or comparatively. For an absolute deter- mination, the crose sectlon of the reaction, the lrradlation flux, and the disintegration rate of the reaction product must be known or determlned. For comparatlive analysis, a substance of unknown ‘mass is irradiated simultaneously with & similar substance of known mass. The positions ol these two subatahces are elther 8ide by slde or, 1f meparated, 1in positlons of like fiux. The reactlon product actlvities of the two samples are compared to glve the relative masses of the starting materlala. The com- pqrative technique 1s, 1n general, much easler to apply. The uncertalnties of many varlables are elimlnated by relative measurements. . Activatlon with thermal -neutrons may be successfully employed as a method-of analysie for--natural uraniuvm, uranium- 236, and the fissionable isotopes of uranium. Nstural uranium consists of U238(99.3¢), 123%(0.72%), and U23*(0.0057%).85L The prinecipal reactiomof thepe nuclides with thermal neutrons are:* 38 1 39 gf ) 239 g- | 239 _a 35 U2 +n-+U2 - Np - Pu lea, % . Half-lives glven below the arrow are taken from the "Table of Isotopes,"” reference 651, The value of V for the fisslon of U235 15 taken from "Neutron Cross Sections," reference 660. 248 y233 + nl - Fission Products + 2.47 neutrons, 1]234 + nl —3 U2350 The amount of natural uranium present in a sample may then be determlned from the amount of U239, Np23% or Pu239 activity - formed after 1rradlation. Measurement of the Pu232 activity, however, requlres elther a fairly large amount of U238, a long irradiation perlod, or a comblnatlon of the two. The amount of natural uranium may also be determlned from the flsslon of uranium-235 elther by (1) fissilon counting the sample, (2) iso- 140 or T6132*’ lating and counting a fisslion product such as Ba or fi3) measuring the total gamma actlvity 1nduced in the sample by a short neutron irradiation-éfii Thermal neutron lrradiatilon of U23* results tn U232 and 1s of little value in the determina- tion of natural uranium. Neutron lrradilatlion of U236 glves U237, a beta-emmiter having a half-life of 6.75 da:,r:s.éél It is readlly 1ldentifiled through its beta decay, assoclated gamma rays, and half-life. Uranlum-238 irradiated with fast neutrons also produces U237, U238(n,2n)U237. The cross sectlon for thls reactlon has been determined with incldent neutron energles from 6 to 10 Mev and at 16 Mev.éél Actlvation analysls by flsslon countling 1s of wvalue only if one fisslonlng nucllide 1s present or if the amounts of other fissionling nuclides present are known and correctlons can be made for them. The same 18 true for the lsolation and deter- mination of fieslon products. Uranlum i1sotopes that are fissionable with thermal neutrons fiogether wlth their thermal 660 neutron fisslon cross sectlicns are:—— y230 25 + 10 barns ye3l 400 = 300 barns *The fisslon product nuclldes Ba140 and Te132 are chosen since they are free from lnterfering reactions and are produced 1n good ylelds. 249 =32 80 + 20 barns 7233 527 = 4 barns 235 582 + 6 barns 0239 14 + 3 barns* Other than U235, U233 is the best uranium isotope to determine by fission counting or flsslon product analysls. Uranlum-232 may posslbly be determined in thie manner. The other lsotopes are of such short half-=11fe that analysis of thelr own radla- tions 1s a much better means for their ldentifilcatlon. Excitatlion functions have been determined for a number of reactliona wlth charged partlcles or gemma rays incldent on uranlum lsotopes. These reactlons may be used for activation analysls. For absolute analysis, 1t should be pointed out that (1) the cross sections reported are sometimes subJect to con- slderable error; (2) energy determinations of the incoming particle or ray are also subject to error; and (3) the reaction product can often be produced by a number of reactlons. Com- parative analysls appears to be a much better method for the determination of uranium. For gamma-ray (bremsstrahlung) activation, slmiltaneous irradiations in a like flux are falrly easy to accomplish. The two samples,; unknown and standard, are mechani- cally rotated In the gamma-ray beam. For charged particle activatlion, the simultaneous irradiation of twd samples in a like flux may require some 1lngenuity on the part of the ex- perimenter.** A partlal list of reactions between uranium isotopes and charged particles or gamma raye for which excitation functions * Plle neutrons. *'Because of the short range of charged particlea, irradiations are generally made with targets attached to or within the vacuum system of the accelerator. To maintaln the system's vacuum requlrements, to coql the samples properly, and to lrradlate the mamples elmultaneously in a like flux may pre- gent some dAiffioulty in equipment design. 250 or 1ndivlidual croes sections have been determined 1s gilven below: Protons 1?30 (p, 530?30 802 Deuterons U238(d’2n)Np238 663,664 U238(d,4n)Np236 663,664 123%(q,p)u?39 804563 12384, t;4, pon)u237 664 U238(d,t)U237 662 U’235(d,n)Np236 §.6_"L'_6_6§ 1235(4, 2n)Np235 664,666 1235 (a. 3n)np23t 664,666 u235(q, 4n)Np=33 566 Alpha particles U238(c.',n)Pu241 u23%(q,n)np?35 666 U234(d,2n)Np234 666 *(a, 3n)np233 288 1233(q,n)np23% 86T 1233(4,2n)Np2 3B EEL U233(4,3n)Np2 32 56T u233(4,an)pa?30 06T 1233 (q,F)zALEL 1235(a,5m) 3% €69 + 1238 (a,p)Np2tl B, p2Hl O 235(q pyNy230 669 U238(a,2n)Pu240 g6l 1230 (a, 30) pu?39 E64 U238(a,4n)Pu238 664,668 1230 (a, pn)np? 0 £69 U238(a,p2n Np239.§§2 )23 869 U236(a,4n)Pu236 668 235(q. ) pu238 664,669 1235(q,2n) pu237 69 235 (. 3n) pu236 661,669 235 (q, kn) pu235 882 Carbon lons 123812 yp)cp2t6 OIL v238(c12, gn)cr2tt E1L U238(012,a4n)0m242 571 Gamma, rays, bremsstrahlun 0238y, n)u237 672,673 v238(y,n) 1% 0235(a,p2n%Np236 £69 U235(a,F) 669 (233, n) 236 669 233(a.2n)pa23 669 1233(4, 3n) pu23% 669 233(a kn)pu33 669 U233 (4. 5n)pu33 669 7233(a, pn)Np232 569 33(q, pan)Np23* 882 1°33(a, p3n) Np®33 882 1233(q,r) 262 U233('YJN) ngl'. The analysls of uranlum by actlivation methods 18 reviewed by Koch,§1§ who also glves references to much of the lilterature. IV-F. Diasolutlon of Uranlum Samples l. Metallle uranium,. EEEE. Uranium metal dissolves 1n nitric acld to form uranyl nltrate. W1lth massive amounts of uranlum the rate of dissolu- tion 1s moderately rapid.EII The reaction between uranium turnings, powder, or sintered metal and nitrlc acid vapors or nitrogen dloxlde may occur with exploslve violence.ézz Oxldes of nltrogen are the principal gaseous products in the dlssolutilon of the metal by HNO The presence of oxygen 1n the dissolver gyatem tends to redzce the emlssion of these oxides.ézg The rate of dissolution of large amounts of metallic uranium may be Increased by the addition of small amounts of .=.’.uli’u1:-ic,§12 phosphoric,ézg&égg or perchloriaégl acld to the nitric acid. HESO4. Hot concentrated sulfuric acld attacks uranium metal slowly forming uranium (IV) sulfate.ézz Sulfurlec acid~hydrogen peroxide mixtures react slowly with the metal at 75°C forming uranyl Bulfate.égg The addition of small amounts of chlorlde or fluorilde to HéSO4 - H202 Pixtures lncreases the dissolution rate.égg H3P04. Cold 85% phosphoric acld attacks uranium metal slowly.ézz Egg;ghtration of the acld by heatlng produces a falrly rapld reaction in which uranium (IV) phosphate 1s formed. If heated too long, a chemically lnert, glassy subetance 18 formed. HClOu. Uranium metal is Ilnert toward cold, dilute perchlorilc acid. As the concentratlon 18 lncreased by heating a point 1s reached at which the reactlon proceeds with violence.ézz&égg Oxlidlzling agents added to dllute perchlorle acld dlssolve the metal.ézz HCl. Concentrated hydrochloric acld vigorously attacks uranium metal. Dllution of the acld dimlnlshee the attack. But even with 4M HC1l there is a rapld evolution of hydrosen.égg A 252 finely dilvided, black preclpitate zoon formas after dissolution begins. This preclpltate 1s not dissolved by heating. Only by the additlon of oxldilzing agents (hydrogen peroxide, bromine, chlorate, nltrate, persulfate, dlchromate, or ferrig ions) does the precipltate dlssolve. Gaseoup chlorlne, aldéed by small amounts of iro; or lodine, also oxldizes and solublllzes the uranium preclpitate. The addition of small amounts of fluosiliecic acl 682,68 or large amounts o¢f phosphorilc :;1.0.1(:]‘:—6--6-g to the hydro- chlorlec acid prevents formation of the black preclpitate during the dissolutlon of uranium metal. HF. The reactlon of hydrofluoric acld wlth uranium metal 1ls slow even at temperatures of 800_90°c,§11 The reaction 1 iInhibited by the formetlon of 1nsoluble UF4 on the surface of the metal. HBr. Hydrobromic acld attacks metalllc uranium in manner similar to, but slower than, hydrochlorilc acid.éll The black preclpitate 1s formed. HI. The reaction between uranium metal and hydricdlc acid ls slow.ézl Organlc acides. Acetlec, formic, proplonlc, and butyrlec aclds react rapldly wlth uranlum 1n the presence of hydrogen chloride.ézz Benzole acld in ether reacts wlth the metal, forming the ben- zoate,ézl Acetyl chlorlde and acetle anhydride react to form. uyranous acetate.2LL Mlscellaneous solvents. Uranium 1s dlssolved In a number of medla other tfian acids:gfiléll&éfig solutlons of heavy metal salts 685 (silver perchlor'a.te‘,-§§-ll cupric ammonium chloride—= or ace= tate§§§), alkaline peroxide solutions (NaOH-H202 or Na,0,-H,0 solutionségz), golutions of bromine and ethyl acetate,§§§L§§§ hydrogen chloride and ethyl aoetate,682 682 hydrogen chlorlde and acetone, and nitrogen dloxlde 'and hydroger. fluoride.2§2 Table XXXVIII denotes qualiltatively some solutions that satisfactdrily dissolve uranium.égg Anodlc dlssclutlon. Metallic uranlum may be dlssolved elec- 253 trolytically by anode oxidation. A varilety of electrolytes have been_used.égg:égg Satisfactory dlesolutions have been made wlth sulfurle acid,682 nitric acid;égl tartarle acid,égl phosphorlc acld contalning n:l.1:z'ate,-§gg and sodlium bicarbonate.égl 2. Alloys of uranlum. The ease with which uranium slloys are dissolved depends largely upon the chemlcal behavlor of the alloylng metal. Larsenégg-has reviewed the dlssolution of some of the more common uranlum alloys. Table XXXVIII summarlzes the effect of various reagents on these alloys. 3« Compounds of uranium. Table II lists solvents for a number of uranium compounds. - General Review references 2, 4, 5, and T (Section I) cover the chemlcal properties of these and other compounds more fully. Table XXXVIII. Reagente for the Dissolutlon of Uranium and Its Alloys.-E S = gatisfactory N = unsatisfactory Descriptilon HNO3 figgia Nig;ic- Hgi + %géic Bra- NaOH=- EtOAc H,0, U S S s S S s S U-Zr N N 8 N N S N U-Nb N N s N N s S U-Fe 3 S S S S S N U-Cr N N N S S s N U-Ru N S N N N N N U-Mo N S N S N S s U-Fissium® N sS N N N N N r-g12 s s U-Pu s< 3 N S S S N 2 R. P. Larsen, reference 682. b Alloyse containing from 1 to 3% Zr, Mo, Ru, Rh, Pd, and Ce. L Fluoride must be added to dissolve Zr. 4 Nitric acld dissolutions leave 381 resldue, but nitric-hydro- fluorlc acld dissolutlons can easlly lead to volatilization of fluosllicice acid. £ Pu itself 1is not reaedlly dissolved in nitric acld, hydrochloric acld belng preferable. 254 The dlssolution of uranium oxldes 1s of conslderable interest slnce uranlium samples prepared as accelerator targets, for neutron irradlations;, or samples found 1n the natufal gtate are frequently 1n the form of oxldes. Also, many compofinds of uranium may be transformed to the oxlde by heating, hydrolysis, or fusion. All of the oxldes, UO 08’ and UOé, are soluble U 37 73 In nitric acld, formlng uranyl nltrate. UO3 1s soluble 1n other minersl acida. U 08 and UO 2 perchlorilc acid;é— They are slowly dissolved in hot concentrated are dlssolved by fumlng wlth gulfurie acida§£ The presence of fluoride accelerates this dissolution.égi Alkallne peroxides react wlth uranium oxides to form soluble peruranates.éfliégl 4, Meteorites, minerals, and ores. The extraction of uranium from natural deposlts may be accomplished by decompositlon and diesolution of the entlre sample 1ncludlng uranlum or by leach=- ing the uranlum from the pample. Grinding and roasting faclll- tate the recovery. Roastling removes organic material. It also helps form soluble uranlum compounds. | Decompositlon of the sample may be accompllshed by acild attack, by fuslon,or by a comblnatlon of the two. Mlneral aclds, indlvidually or in comblnatlon, may be used. The presence of hydrofluoric acld generally alds in dlssolution. Ores, sand, etc. may be fused with sodlium carbonate, so@ium hydroxilde, so&ium peroxlde, sodlum blsulfate, sodium chlorlide and sodium hydroxide, ammonium sulfate, potassium bifluoride, and mag= neslum oxide.ll;fi&ég& The melt ls solublllzed in water orlacid and the separation of uranium made by procedures outlined in Seetlon IV=-D. Rodden and 1.'Ja.r-f.'--:'3‘--ll have described a number of procedures ln whlch uranium was made soluble by acld attack or by fusion methods. The recovery of uranlum from monazite sands hae been reported by Calklns, gg_géfégi Acld and alkallne leaching &'¢ used on an industrial scale ' for the recovery of uranium from its ores. In acld leachilng, 255 hydrochloric, nitric, or sulfuric aold may be uaedel Indus- trially, sulfuric acld is used because of itq economy. Oxidizing agents (Fe(III), MnO, uranium (VI). A separation of uranium and thorium with an oxalie acld-nitric aocld leach solutlon has been raported.'§2§ » eta.) are used to convert uranium (IV) to In alkaline leaching, various ocombinations of alkaline carbonates, hydroxides, and peroxides have been used.: Indus- trially, uranium is dissolved by alkalline ocarbonates as the U02(003lg' complex. - Oxygen or other sultable oxidants are used- to oonvert uranium (IV) to uranium (VI). Hydroxyl lons are formed by the dissolution of uranium in carbonate solutions. The presence of bloarbonate lon in the disaolvins'solution prevents the preciplitation of uranium. The recovery of uranlum by acid and alkaline leaching 18 reviewed in General Review reference 13 (Section I). 5. Blologlcal samples. The determination of uranium in blolo- g;cfil fiamples 18 reviewed by Steadman.égé- Uranlum may he ex= traocoted and determined directly from liquld samples. The sample may also be ashed, as are solid samples, prior to uranium ex- traction. Ashling fiay be carried cut as a wet or dry process. Wet-ashlng 18 commonly done wlth a nitric acld solutiocn. Ashlng may be completed wlth perchloric acld. However, extreme cautlon must be exerclsed when heating organic materials with perchlorilc acid. The ashed residue 1s dissolved in aocild and the uranium determination continued from there. Wet=ashling need not be ‘carrled to completion. Analysis may be made upon the sample after 1t has been thoroughly digested in acid. 6. Alr dust samples. Samples of alr dust are commonly collected on filter papera. The uranium may be dissolved by digeating the sample in nitrlc acld solution or the sample may be ashed and the residue dlssolved 1n aold. 256 V. Collectlon of Detalled Procedures A prodedure for the determination of uranium may entail one or more purificatlion steps a8 outllined 1n the preceding sections. For ex#mple, uranium may be separated from Impuritles by a serles of solvent extractions with one or more different solvents. These may be interspersed wlth precipitation and/or lon exchange methods. The procedures described hereln have been gathered from .projeet reports, the.open literature, and by private communicatlon. Only a limlted number are presented. They have been selected.because they represent many of the Beparation methode already descrlibed or because they represent different problems in handling samples: problems of dissolution, extrfiction in the presence of hlgh beta=gamma activity, etc. A number of the procedures described do not make use of the ra- diometrlc determination of uranlum. The method of separation in these procedures, however, 1s applicable to radlochemlcal ~analysls and is, therefore,; included. A number of papers and reports describe, in detall, procedures for the determinatiofi of uraniuym. Thése 8should be noted. The work of Rodden end Warfgi has frequently been mentloned in this paper. In addl- tion to procedures for the precipitatlion, solvent extractlon, volatilizatlon, and electrodeposition of uranium, these authors have presented a number of selected procedures for the solutlon of ores and minerals and the separation and determlnation of uranium. Procedures for the anélyticalldetermination in naturally occurring materlials have also been described by Rodden and Trggonning,ééé'Grimaldi, May, Fletcher, and Titcomb,égz Schoeller emd"P-m»,'ell,i?-92 and in the "Handbook of Chemical Determination of Uranium in Minerals and Ores."§2§ The recent publlcatlon by HooreEzl on extraction with amines contalne a collectlon of pro- cedures, many of whlch have to do with the separation of uranium. 257 IROCEDURE 1: Uranilum-237-. Source: B. Warren, LA-1567 (1953) p. 18. Editort's note: Uranlum-237 may be separated from fission pro- ducts, neptunium, and plutonium more easlly by lon exchange and/or solvent extractlion techniques (see, for example, Procedure 7). The following procedure 1s, however, an excellent example of uranium purification by precipltation methods. l. Introductilon The significant steps 1n the determinatilon of U237 in ma- terlials contalning flasslon products, neptunium and plutonium are the following. Rare-earth, neptunium, and plutonlum actlvities are removed by appropriate lanthanum fluoride scavenglng steps in the presence of hydroxylamlne hydrochloride. The latter reagent serves to reduce both neptunium and plutonlum so that they may be carried down, and also to complex uranium and pre-~ vent 1ts later removal in lron scavenglng steps. Barlum and Zlrconlum are preclpltated by barium fluozlirconate scavenglng. followlng a cycle of ferric hydroxide scavenging and ammonium dluranate precipltatlion steps, uranium 18 reduced by zlnc metal in hydrochloric acld medium and precipltated, presumably as U(OH)u,_with ammonlum hydroxlide. The uranium 1s further purifiled by alternate conversilons to tetrafluoride and hydroxide. 24.1d Th234(Ux1) which has grown in from =38 is removed by a zirconium lodate scavenge and the uranlum 1s converted to ammonium dluranate. Uranium 1s finally plated from nitric acld hedium onto a platinum foll. \After flaming of the foll and welghlng, uranium is beta; counted as U308' Chemlcal ylelds average 50 to 65%. Quadrupli- cate determinations require approximately 8 hours. 2. Reagents U238 carrier: 1 ml containing 10 mg of (5000/1) uranium. Pre- paration: Welgh out 1 gm of U metal, dlssolve in cone, HNO3, transfer to a 100-ml volumetrlc flask. Make up to volume, adjusting the flnal solutilon 258 PROCEDURE 1 (Continued) to 3M in HN03. The carrler 1s standardized by plpeting 1 ml aliquots lnto a 000=Coors procelaln cruclble, evaporating to dryness, 1gniting at 800° for 45 min, and welghing as U308' La carrier: 10 mg Le/ml (added as La(N03)3 . 6H20 in H20) Ba carrler: 10 mg Ba/ml (added as Ba(No3)2 in H20) Zr carrier: 10 mg 2r/ml (added as ZrO(N03)2 . 2Hé0 in 1M HNO Fe carrier: 10 mg Fe/ml (added as Fe(NO3)3 * 9H,0 in very dilute HN03) HCl: conc. HN03: 1M HN03: BE HNO3: conc. HF: conec. HESOM: cOone. HI03: 0.35M NHuoH: conc. NH,OH - HCl: 5M 4% aqueous (NHy),C50y Bry: liquid Zn metal: 20 mesh, granular Methanol: anhydrous Methyl red indicator solution: 0.1% in 90% ethanol. 3. Equipment Flsher burner Centrifuge Block for holding centrifuge tubes Lo-m1l centrifuge tubes: Pyrex 8140 (10 per sample) 000-Coorse porcelain crucibles (one per standardization) Pt-tipped tweezers Plpets: assorted slzesa 259 PROCEDURE 1 (Continued) Stirring rods Plating assembly: 1 cell per allquot of sample Source of current - Fisher Powerhouse (D.C.) with varlable resistance in series wlth cells. Cell - Brasé base (3" x 3") for holding Pt cathode; 5-mil Pt circular 2" diameter disk (cathode); gasket (Koroseal-Upholstery 36681) to seal cathode and chimney; glass chimney, 2" diameter, 4" high, with 4 ears at helght of 3"; 1 1/4" steel springs for holding chimney to base; rotating Pt anode. The cell is heated for 1 3/4 hours at 105° after assembly to insure formation of s8eal between glass and Pt. Water bath for cell - Autemp heater; 6" crystallizing dish (for water bath); rubber pad for holding cell. 4, Procedure Step 1. Add 1 ml of sfandard U carrier to an allquot of sample in a 40-ml long taper centrifuge tube. Dilute to about 10 ml, heat to bolllng, and preclpitate (NH1|_)2U207 by the drop- wlse additlon of conec. NH40H. Step 2. Centrifuge and dlscard the supernate. Step 3. Dissolve the preelpltate in 1 to 2 ml of 1M HN03, add 5.4 ml of H,0, 3 drops of La carrier, and 10 drops of 5M NHEOH « HCl. Allow to stand for 5 min. Step 4. Add 3 drops of conc. HF and allow to stand for 5 " min. Centrifuge for 5 min, transfer supernaté to a 4%0-ml centrifuge tube, and dliscerd the preclpitate. Step 5.. Add 3 dPOps of 1a carrlier and let stand for 5 min. Centrifuge for 5 min, transfer supernate to a 40-ml centrifuge tube, and discard the precipitate. Step 6. Add 3 drops of Zr carrler and 15 drops of Ba 260 PROCEDURE 1 (Continued) carrier. Centrifuge for 5 min and trensfer the supernate to a 40-ml1 centrifuge tube, dilscarding the precipltate. Step 7. Add 4 drops of conc. H,80, and centrifuge for 5 min. Transfer the supernate to a 4#0-ml centrifuge tube and dlscard the precipiltate. Step 8. Add 2 drops of Fe carrler, heat the solution to bolling, and preclpltate Fe(OH)3 by the addition of conc. NH,OH. Cool the tube under cold HEO’ centrifuge for 2;1/2 min, and transfer the supernate to a 40-ml centrifuge tube, discarding the precipiltate. Step 9. Add O.% to 0.5 ml of 1llquid Br, (Note 1) slowly to slighf excese and boll the solution to a light yellow color. Add conc. NH,OH until (NH4)2U20 T der cold water, centrlfuge, and save the precilpltate. preclpltate forms. Cool un- Step 10. Add 1 to 2 ml of 1M HNO, and 10 ml of H,O, heat 3 2 the solutlon to bolling, and add conc. NH40H to repreclpiltate (NH4)2U207. Centrifuge and save the precipiltate. Step 11. Add 1 to 2 ml of 1M HNO 10 ml1 of H,O0, 10 dropse 37 2 of 5M NH,OH * HCl, and 2 drops of Fe carrler. Let stand for 2 5 min. Heat the solutlon to boiling and precipitate Fe(OH)3 by addltlon of conc, NHuoH. Cool the tube under cold HQO, centrifuge for 2-1/2 mln, and transfer the supernate to a 40- ml centrifuge tube, dlscardlng the preclpltate. Step 12. Repeat Step 9. Step 13. Add 1 ml of conec. HC1l, 10 ml of H20, heat the solution to boililng and precifiitate (NH4)2U'207 with conc. NH,OH. Cool the tube, centrifuge, and save the preclpltate. Step 14%. Dlssolve the precipltate in 1 ml of conc. HC1l and 10 ml of H,0. Add 2 gm of Zn metal (20 mesh, granular), and heat the mixture untll the solution turns brown. Heat 1 addi- tlonal minute. 261 PROCEDURE 1 (Continued) Step 15. Let etand untll the vigorous gas evolutlon subsldes and decant iInto a 40-ml centrifuge tube. Discard the Zn. Step 16. Heat the solutlion to bolling and preclpiltate U(OH)4 (?) with conec. NH),OH. (The precipitate will be greenish- black.) Centrifuge and save the precipitate. Step 17. Dissolve the preclpltate 1n 10 drops of conc. HCI. Add 5 ml of Héo and 4 drops of conc. HF; Stir vigorously until UF), precipltates, add 7 drops of conc. NH40H and stir. Cen- trifuge 5 min and save the precipitate. Step 18. Add 1 ml of cone. HC1l, heat slightly, add 10 ml of H20, and heat the solution.to bolling (the precipitate should dissolve). Add conc. NH)OH and precipitate U(OH)u (?) (greenish- black precipitate). Step 19. Repeat Step 17, except that 4 ml of H,0 are added Instead of 5. Step 20, Add 1 ml of conc. HNO3 and heat until NO, ceases to be evolved. Add 10 ml of H,0 and precipitate (NH4)2U207 wilth cone. NH40H. Centrilfuge, discard the supernate, and dissolve the precipltate In 1 ml of conc. HNOB. Step 21. Add 10 ml of H2O, 4 drops of Zr cerrler, and 1 ml of 0.35M HI03. Centrifuge, transfer the supernate to a 40-ml centrifuge tube, and dlscard the preclpltate. Step 22. Heat the solutlon to bolling and preclpltate (NH4)2Ué07 with cone. NH),OH. Centrifuge and discard the supernate. Step 23. Dissolve the precilpltate in 1 to 2 ml of lfl_HNOS, dllute with 10 ml of Héo, and centrifuge. Transfer the super= nate to a 40-ml centrifuge tube and discard the precipltate. Step 24. Reprecipitate (NH4)2U'207 by bolling the solution and adding conc. NHAOH. Centrifuge and save the precipltate. Step 25. Add 5 drops of 8M HNO; and transfer to the plating - cell which contains 10 ml of H,0 and 3 drops of 8M HNOB. Rinse the centrifuge tube with three washes each conflisting of 5 262 PROCEDURE 1 (Continued) drops of 8M HNO3 and 0.5 ml of B,0, transferring the washingfi to the plating cell. Step 26. Add 10 ml of 4% (NH4)20204 and wash the cell walls down wlth approximately 5 ml of Héo. The total volume 1n the cell should be about 40 ml. Step 27. Add 5 drops of methyl red solutlion, and conc. NH40H drop-wise until the solution turns yellow. Add BEHNO3 until the solution turns red or orange (one drop 1s usually required); then add 3 drops of HN03 in excess. Step 28. Plate for 1-1/2 hours at 1.5 amp and 8 volte at 80 to 90°. For the first 30 min, at 10-min intervals add sufficienf 8M HNO5 to make the solution red to methyl red. At 40 min, add 3 drops of conc. NH40H, or enough to make the solu- tion yellow to the 1ndicator. Step 29. Wash down the cell walls with H20 to replenish that lost by evaporation, and continue electrolysls for ah addltional 50 miln. Step 30. Remove plate, wash with H20 and methanol. Flame plate for 1 min. Cool, welgh as U308’ mount, and count. Correct for Th234 (le) activity (see accompanying figure). Notes 1. Liquid Br, destroys NH,OH and also the uranium-hydroxylamine 2 complex. 263 COUNTS /MINUTE 1.0 PROCEDURE 1 (Continued) 1 1r 1 vr 1 v rt - n — -] e - _ o -9 . o 0 © c = ~ o ° J o - ~ O L 0 - _ o _ O O I—o —_ ~ - |.o —f r—- - L o b L by gy : O 2 4 e 8 10 12 |14 DAYS CORRECTION FOR UX; ACTIVITY/mg U3Qq ON PLATE. Procedure |. 264 PROOCEDURE 2: Purification of Uranlum-240. Source: E. K. Hyde and M. H. Studler, ANL-4182 (1948). EE&Sor's note: The followlng procedure was uged toUngify U formed by the second order neutron capture of « The principal decontamlnating etep 18 the ether extractlon of urenlum from a reduclng agueous solution. Uranium la further purified by a number of precipltatlons that are not described In detall. These, however, are falrly easy to perform. Irradiation and Chemlcal Procedure Two grams of depleted uranium (1 part 0235 per 30,000 parts U238) &as U308 in a small 2g alumlnum capsule was lrradiated 1n the Hanford plle for 12 hours including time for startup and shutdown. B81x hours after the end of the irradiation the cap- sule and 1lts contents were dissolved In nltrlc acld, using mercuric ion as catalyst for dlssolving the alumlnum. The uranlum was eXtracted batchwlse, the dlssolved aluminum serving a8 a salting agent. The ether contalning the uranlum was then passed through two statlc wash columns packed with 3/32 inch stalnless steel helices and filled with a solution 10M in ammonium nitrate, 0.1 M in nitric acid, 0.0l N in ferrous ilon and 0.1 M in urea. Neptunlum was reduced by the aluminum 1n the dissolver and by the ferrous lon 1n the wash colummg to an unextractable oxldation state (Np IV and Np V). Additional ether was passed through the columns to strip out the uranium. These operatlone wWere carried out by remote control behind lead shielding. The lnltial dissolver solution measured roughly 50 roentgens per hour at 8 i1nches. The ether solution emerging from the second column and contalning the uranlum measured only about 3 mr per hour at the surface, and most of thils was ether- soluble iodine fileslon product activity. The uranium was ex- tracted from the ether into an aqueocus ammonium sulfate solu- tion and washed several times wlth ether to remove lodlne actlvity. LaF3 was preclplitated from the uranjl nitrate solu=- tion after reduction wlth sulfur dloxide to remove any traces of Np239 which might have come through the ether extractlon. 265 PROCEDURE 2 (Continued) r The uranium was further purified by precipitation as dluranate, sodium uranyl acetate, and peroxide and by a final ether ex- traotion. Throughout this final serles of purlflcatlons there was no detectable decrease 1n p-activity; thie 1indicates that the uranlum was radioactivg}y pure. Small aliquots of thelfinal uranium solutlon were evaporated on platinum dises and ignited to U308 to study changes 1in activity. The remaining uranium solutlon was used for extractlon of neptunium daughter fractlons. PROCEDURE 3: Purification of Irradiated U23°, Source: S. Fried and H. Selig, Private communlcation. Editor's note: The present procedure was used 1n an experliment deséfig?d to measure the 525 mal neutron fisslon cross sectlon of The amount of that can be tolerated 1n such an experiment 1ls very small. Two criterla were used in selectlng the purification steps in the followlng procedure: 1) To obtaln uranium free of fission products and other extraneous activitles wilithout 1ntroducing contamlnant normal uranium 1in the procedure.f _ 2) The initial part should lend itself easlly to remote control manipulation. *The reagents used were carefully purlfied. Thus, the niltriec acld and perchloric acid were redistilled In a quartz still. The NH4N0 was prepared from gaseous ammonia and distllied HNO3. 3 The HCl was prepared by passing HC1l gas into triply distllled H20, etec. 266 PROCEDURE 3 (Continued) Procedure: A. In Cave The irradiated uranium oxide (~0.3 mg) was dlssolved in concentrated HNO, and made up to 2 M 1n HNO; with distilled H,0 to give total volume of about 15 ml. Some Fe'T was added to keep Pu and Np in +%4 étate; The solutlon was saturated with NH4N03 and contacted four times with 10 ml portions of ether. Each contact was scrubbed twlce with 2 L‘.[_HNO3 saturated with NH4N03o The comblned ether extracts were back extracted three times wlth 5 ml portions of H20. The'HEO strip wae evaporated to dryneas and trested with HCl to destroy NH4N03 carried over. B. Outsilde Cave The sample could now be handled easlly outslde the cave wlth a minimum ‘of shielding, moat of the actlvity being dus to U237. A mass spectrometrlc analysls showed 1t contalned 0.5 welght % of U3/, A flsslon count showed that additional purl- 238 fication was necessary to remove Np formed by (n,y) on Np237 whlch had bullt up during lrradiation. The sample was taken up 1ln about 0.5 ml 6 N HC1l and put on a small Dowex-1l column and washed. The Np comes off 1n 6 N HCl. Finally the uranium was eluted with 0.5 M HCl. The eluate was evaporated to dryness and taken up in 0.2 ml of 5 M HCl, 0.1 M KI and 0.05 M N2H40H » 2HCl. This was heated at 90° for 2 minutes, diluted to 0.5 M in HCl and TTA extracted twice for 15 minutee. The crilginal fraction was washed twice with benzene and evaporated to drynese. | In order to clean up the uranium for a mass apectrometric analysils, 1t was subJected to another ether extraction as in the first fitep. After the NH4N03 was destroyed the sample was fumed with HGlOu to destroy any organic resldue from the ether extraction. ~ 267 PROCEDURE 4: Uranlum and Plutonium Analysis Source: B. F. Rlder, J. L. Rusesell, Jr., D. W. Harris, J. P. Peterson, Jr., GEAP-3373 (1960). Samples of dissolved lrradlated fuel contaln highly radloactlve fission products. For thls reason, uranlum and plutonium are separated prior to analysis. The followlng pro- cedure glves a good yleld together with a good deéontamination factor. Reagents: 1. Distilled cone. HNO3. 2. 2 M HNO3 - dlstlilled cone., HN03, double dilstllled H20. 3 U-~-233 solutlion, standardized. 4, Pu-236 solution, standardized. 5. KBr03 - Crystals, Reagent Grade. Low natural U blank. 6. 8 M NH4N03 in2 M HNO3 - Place 200 ml distilled 16 M HNO 7 8. 9. 10. 1. 12. 13. 14, 15. 3 + 100 ml double distilled H20 in a large beaker. Bubble NH3 gas through sclution until basic to pH paper. DBoil off excess NH3 (solution neutral). Transfer to mixing eylinder, add 50 ml of distllled 16 M HNO dilute to 400 3. ml. Check density of solution (1.31 * 0.0l at 20°C.). Hexone - distilled. HC1 - C.P. reagent. Low natural U blank. 1 M HNO, - distllled conc. HN03, doub;e distilled H20° 304 H2OZ - meets A.C.S. specification, low natural U blank. 0.2 M T.T.A. in xylene - 4.44 gm T.T.A. dissolved in 100 ml distilled xylene. Xylene = distilled. Efher - distllled. 0.05 EHNO3 - distilled conc. HNO3, double distilled H20. H20 ~ double distilled. Glassware: All glassaware used 1s Pyrex which hae been soaked overnight 1in 268 PROCEDURE 4 (Continued) 50% HNO3 and rineed with double dlstllled water. Plpets are rinsed with 50% HNO 3 and double distilled water before uslng. Separation and Decontamination Procedure: 1. " 1mlof 8 M NH4N0 Place the allquot for analysis in a 15 ml cone and evaporate to about 1 ml. Add a sultable U-233 and Pu-236 spike, one drop conc. nitric aceld, and several KBrO3 cryatals. Allow to stand for 1 hour to allow oxldatlon of Pu to Pu02++. Add 1.5ml 8 M NH4NO3 in 2 E.HNos, and evaporate to about 2 ml. Prepare 2 scrub solutions ln separate 15 ml cones, contalning 3 in 2 _]fl_HNO3 and about 10 mge KBr03. Preoxidlze about 10 ml hexone with 2 ml of 2 M HNO3 and KBr03. Keep covered untll ready for use, Extract the U and Pu four times for flve minutes with 2 ml portions of hexone (methyl ilsobutyl ketone), adding 1 drop of 16'§ HNO3 to the orilgilnal solutlon after each extractlon. Scrub each extraet 1n turn with the two solutions prepared In step 3.' Strlp the comblned hexone extracts with five 2 ml portlons of H20° Evaporate the comblned aquecus portions to dryness, add a few drops of HNO. and HCl, take to dryness. Evaporate to dryness wilth HNO3 uider a8 gentle stream of pure nltrogen on a bolllng water bath. Prepare 3 ml of 1 E_I.HNO3 and 1 drop of 30% H202, add 1 ml to the Pu and U resldue from step 5 and two 1 ml portions to separate 15 ml cones. Extract 1mmedlately the Pu 2 times for 20 mln. with 2 ml portions of 0.2 M T.T.A. (thenoyltrifluoroacetone) in xylene. Scrub each in turn with solutions prepared in step 6. Save the aqueous phase for uranium. Combine the T.T.A. extracts and add a few crystals of trichloroacetic acid. 269 10. 1l. 12, 13. 1L, 15. PROCEDURE 4 (Continued) Mount the combined T.T.A. extracts on a platinum plate for alpha pulse analysls. After pulse analysis, remove the Pu for mass analysls as follows: Cover disc wlth HF. Evaporate to dryness under a heat lamp. Agaln cover dilsc with HF and evaporate to dryneses. Cover dlsc wlth cono. HNO3 and evaporate to dryness. Repeat 3 or 4 timee. Cover disc wilth cone. nitric, re- flux a few seconds, and transfer with a plpet to a 15 ml cone. Repeat 3 ar U4 times. Evaporate the comblned conc. HNO3 refluxes to dryness. Treat resldue wlth aqua regla and evaporate to dryness. Evaporate to dryness with conec. HNO3 on a bolling water bath several times. Add 50 * of 0.01 M HNO, to the evapor- 3 ated sample and submlt sample for mass epectrographic analysis. Wash the original 1 M HNO_ uranium fraction (Step 7) with 3 xylene. Add 1 drop of HNO_, and 3 drops of HCl to the washed 1 M HNO3 and reflux3for about one-half hour to de- setroy the organic present. Evaporate to dryness, flame gontly to destroy organic-matter and dlesoclve the resldue wlth 2 drops HNO3 and evaporate to dryness on a water tath. Pipette three 1 ml portlons.of 8 M NH,NO; in 2 M HNO,, dlssolve the evaporated U fraetlion 1n one 1 ml portion. Place the other 2 portions ln two 15 ml cones for scrub solutions., Extract the U with four 2 ml portlons of dlethyl ether, add~ ing 100 X of conec. HNO3 before each extractilon. Sorub each extract In turn with 2 serub solutilons prepared in Step 12. Evaporate the comblned ether extracts over 1 ml of HEO in a 15 ml econe, Evaporate.to dryness. Add 3 drops of HC1l and 1 drop of HN03, and evaporate to dry- 270 PROCEDURE 4 (Continued) ness repeatedly untll the organlc ls destroyed. Flame gently to expell ammonlum salte. Then dlssolve 1n HNO3 and evap= orgte to dryness on a water bath. Add 50 : of 0,05 l\_d.HNO3 to the dry cone and submlt sample for masse spectrographic analysls. Plutonlum Calculatlon: To determine the amount of Pu in the origlnal sample, 1t 13 necessary to measure 1ln a Frilach chamber the alpha spectrum of the plate prepared in Step 8. The ratio of Pu-239 and Pu-240 activity to Pu-236 activity is calculated. If the ratio 1s mul- tiplied by the original activity of Pu-236 fidded, the original activity of Pu-239 plus Pu-240 can be obtalned. From the mass anslysis a Pu-239 to Pu=-240 atom retlo 1s obtained. The speci- fic actlivity of the mixture 1s calculated from that of the indl- vidual isotopes. The Pu-239 plus Pu-240 activity can be con- verted to Pu-239 plus Pu-240 welght by dividing this activity by the speclfic activity of the mixture. Uranlum Calculation: The ratio of the various U lsotopes o U-233 from the mass spectrometer data 1s multiplled by the amount of U-233 splke originally added to the sample to obtaln the amount of each uranlum isctope present 1ln the original sample. PROCEDURE 5: Spectrophotometrlec Exftraction Methods Specifilo for Uranium. Source: W. J. Maeck, G. L. Booman, M. C. Elliott, and J. E. Rein, Anals Chem. 31, 1130 (1959). Abstract Uranium as tetrapropylammonium uranyl trinltrate 1s quan- 271 PROCEDURE 5 (Continued) tltatively separated from largé quantities of dlverse ions by extraction into methyl 1sobutyl ketone (4-methyl-2-pentanone) from an acld-deflcient aluminum nltrate salting solutlon. Milll- gram levels are determined by a direct absofbance measurement of the trinitrate complex 1ln the separated organic phase at 352 my. Mlerogram amounts are determined by adding dibenzoyl- methane (1,3-diphenyl-l,3-propanedione) in an ethyl alcohol- pyridine mixture to the separated organic phase and measuring the absorbance of the chelate at 415 mu. The coefficlent of variation 18 less than 1% at the 10-mg. and 25-y levels. The 1imit of sensitivity 1s 0.8 v for the dlbenzoylmethane method. Apparatus and Reagents Absorbance measurements of the tetrapropylammonlium uranyl trinitrate complex were made wilth a Cary Model 14 recording Bpectrophotometer and l-cm. Corex cellg. A Teflon 9 x 9 x 6 mm. spacer placed in the bottom of the cells permlits absorbance measurements wlith 2 ml. of sample. Abaorbance measurgments of ‘the dlbenzoylmethane complex were made wlth a Beckman DU spec= trophotometer and 5-c¢m. Corex cells. Extractions were made 1in 125 x 15 mm. teat tubes with polyethylene stoppers. A mechanlcal extraction device? was used for agltatlon. Reagent grade inorganic and Eastman Kodak Co. White Label organlc chemlcala were used without purlficatlon. Dilstilled water was used throughout. The uranlum solutions were pfepared by dlasolving purlfled black oxlde; U308‘ in a slight excees of nitric acid, and making to volume with water. The dibenzoylmethahe reagent 1s prepared by dlssolving 0.1140 gram'of dibenzoylmethane in 500 ml. of a 5% solution (ve/v.) of ethyl alecohol in pyridine. Salting and Scrub Solutions. A. 0.005M Tetrapropylammonium 272 PROCEDURE 5 (Continued) Nitrate, 1N Acld-Deflclent Salting Solutlon. Place 1050 grams of aluminum nltrate nonahydfate in a 2=l1liter beaker and add water to a volume of 850 mi. Heabt, and after dissolutlion add 67.5 ml. of concentrated ammonium hydroxide. Stir for several minutes until the hydroxlde preclpitate dilssolves. Cool to less than 50°C.,add 10 ml. of 10# tetrapropylammonium hydroxide, and stir untll dilssolved. - Transfer to a l=llter volumetrlc flaek and make to volume wlith water. A prellminary extractlon with methyi lsocbutyl ketone 1ls suggested to remove uranlum contaminatlon in whlch case tetrapropylammonium hydroxide will have to be re-added. B. 0.025M Tetrapropylammonium Nitrate, 1N Acld-Defilolent Salting Solutlon. Same as A except that 50 ml. of 10% tetra=- propylammonium hydroxide 1s used. C. 0.25M Tetrapropylammonium Nitrate, 1N Acld-Deficlent Salting Solutilon. Neutralize 100 ml. of 10% tetrapropylammonium hydroxlde to pH 7 with 5N nitric acld. Transfer to a large evaporating dish and let stand untll a thlck crystal slurry forms (which may take as long as 4 days). Place 210 grams of aluminum nitrate nonahydrate in a 400-ml. beaker and transfer the tetrapropylammonlum nitrate cryetals Into the beaker wlth 20 ml. of water. Stilr and add water to a volume of approximately 180 mi. Add 13.5 ml. of concentrated ammonium hydroxide and fstir until dissolution 1s complete {which may require several hours). Transfer to a 200-ml. volumetric flask and make to volume wlth water. D. Scrub Solutlon for Dibenzoylmethane Method. Add 940 grams of aluminum nltrate nonahydrate, 33 grams of tartarilc acld, 31 grams of oxalic acld, and 64 grams of (ethylenedinitrilo)- -~ tetraacetic aclid to 100 ml. of water and 150 ml. of concentrated ammonium hydroxlide. Heat with stirring until dissolved. Cool, 273 PROCEDURE 5 (Continued) filter, transfer to a l-llter volumetric flask, and make to volume wlth water. Remove uranium contamlnation by a methyl 1sobutyl ketone extractlon. E. Speclal Solutlions. The following salting and scrudb golutlone are used in the dibenzoylmethane method for samples containing cerium(IV) or thorium. 1. Prepare an alumlnum nitrate saltling solutlon as A, but omlt the tetrapropylemmonlum hydroxilde. 2. Prepare a sc¢rub solution by dissolving 154 grams of ammonlum acetate and 20 grams of the sodlum salt of dlethyldi- thlocarbamate In water to a volume of approximately 900 ml. AdJust to pH 7, fllter, and make to a l-liter volume wlth water. 3. Prepare a mercurlc nltrate solution by dissblving 0.063 gram of mercurlc nitrate in 90 ml. of 1N nitric acld and making to a2 100-ml. volume wlth 1N nitrlc acld. Procedures Milligrafi Amounts of Uranium. Wlth aqueoua samples of 0.5 ml. or less and contalning up to 2 meq. of acld, 0.5 to 12 mg. of uranium can be extracted from a saltling solution whilch is 0.025M in tetrapropylammonlium nltrate and 1N acid—deficient. Samples of hlgh acldlty should be neutrallzed to less than 2 meq. of free acld, or a salting solution which 1s 2N acid-deficiefit can be used for samples contalning up to 6 meq. of acild. If cerium(IV) and thorium are present, the absorbance from uranium will be maximum 1f the combined uranium(VI), thorium, and cer= 1um(IV) do not exceed 0.05 mmole in the sample aliguot. Samples that contain more than 0.05 mmole of comblned uranium, cerium- (Iv), and/or thorium can be analyzed after dilutlon, provided the resulting sample aliquot contalns more than 0.5 mg. of uranium. If this condltlon cannot he met, the 0.25M tetrapro- pylammonlum nltrate salting solutlon 1s used, which can accommo- 274 PROCEDURE 5 (Continued) date up to 0.5 mmole of comblned uranium, cerium(IV), and thorlum. Pipet a sample of 0.500 ml. or less, contalning from 0.5 to 12 mg. of uranium, into a test tube contalning 4.0 ml. of salting solution B or C. Add 2.0 ml. of methyl lsobutyl ketone, stopper, and extract for 3 mlmutes. Centrifuge to facllitate phase separation. Transfer as much as possible of the organlec phase with a micropipet to a l-om. cell contalning the Teflon spacer. Measure the absorbance at 452 mu agalnst & blank pre- pared by substituting 1N nitric acid for the sample. Microgram Amounts of Uranium. Aqueous sample allquote containing up to 2 mg. of uranium and as much as &E in acid can be quantitatively extracted from a salting solution 0.005M in tetrapropylammonium nitrate? . Neutrallze samples of higher acldity to less than 8N before extractlon. SAMPLES WITHOUT CERIUM(IV) AND THORTUM. Pipet a sample of 0.500 ml. or less, containing from 0.8 to 75 ¥ of uranium, into 2 test tube contalnlng 5.0 ml. of salting solutlon A. Add 2.0 ml. of methyl 1sobutyl ketone, stopper, and extract for 3 minutes. Centrifuge to facllitate phase separation. Transfer as much as possible of the organic phase to a test tube con- taining 5.0 ml. of scrub solution D, stopper, and mix for 3 minutee. Centrifuge to facllitate phase separatlon. Remove a 1.00-ml. aliguot of the organlc phase and transfer to a 25- ml. flask. Add 15 ml. of the dibenzoylmethane-pyridlne reagent and théroughly mix. Allow to stand 15 mlnutee, tranasfer to a 5-cm. Corex cell, and measure the absorbance at 415 mp oompared to a blank prepared by substituting 1N nltric acld for the sam- ple aliquot. SAMPLES CONTAINING CERIUM(IV) OR THORIUM. Pilpet a sample of 0.500 ml. or less, contalning from 0.8 to 75 v of uranium, 275 PROCEDURE 5 (Continued) into a test tube contalning 5.0 ml. of the salting solutlon E-1. Add 4.0 ml. of methyl isobutyl ketone, stopper, and extract for 3 mlnutes., Centrifuge to facllltate phase separatlion. Transfer as much as poaslble of the organlc phase to another tube cone taining 5.0 ml. of scrub solutlon E-2, stopper, and mix for 20 minutes. Centrlfuge as before. Tranafer at least 3 ml. of the organlc phase to a fest tube contalnlng 5.0 ml. of saltlng solu- tion E-1. Add 0.5 ml. of scrub solutlon E-3, stopper; mix for 10 minutes, and centrifuge. Remove a 2.00-ml. allquot of the organlc phase and transfer to a 25-ml. flask. Add 15 ml. of the dibenzoylmethane-pyrldine reagent and thoroughly mix. Let stand 15 minutes, transfer to a 5.0-cm. Corex cell, and measure the absorbance at 415 mp compéred to a blank prepared by substitute ing 1N nitrilc acid for the sample allquot, Calibration. Two different standards contalning levels of uranium sequlvalent to approximately 0.1 and 0.7 absorbance are processed. The concentration of samples 1s establlshed by the average absorptivity of these standards provlded agreement within statlstical 1imits (95% confidence level) 1s obtained. 2 . J. Maeck, ¢. L, Booman, M. C. Elllott, J. E. Rein, Anal. Chem. 30, 1902 (1958). PROCEDURE 6: Determination of Uranium in Uranium Concentrates. Source: R. J. Guest and J. B. Zimmerman, Anal. Chem. 27, 931 (1955). Abstract A method 1s described for the determinatlion of uranium in high grade uranium material. Uranium ls peparated from contamlnants by means of an ethyl acetate extraction using aluminum nitrate as a salting agent. After the uranium hase been strlipped from the ethyl acetate 276 PROCEDURE 6 (Continued) layer by means of water, colorlmetrlc determination of the uranium is carrled out by the sodlum hydroxlde-hydrogen peroxlde method. The procedure 1B accurate, rapld, and easlly adaptable to routine work. Reagents and Apparatus Reagents. Ethyl acetate (Merck, reagent grade). ALUMINUM NITRATE SALTING SOLUTION. Place approximately 450 grams of reagent grade (Mallinckrodt) alumlnum-nitrate [Al(NO3)3- 9H201 in a 600-ml. beaker and add 25 to 50 ml. of distillled water. Cover the beaker and heat the mixture on a hot plate. If & clear solutlon does not result after 5 to 10 minutes of bolling, add 20 ml. of water, and contlinue the bolling for 5 more mlinutea. Repeat this step untll a clear solutlon 1s obtalned after bolling. Remove the cover glass and concentrate the solutlon by bollling untll a bolling point of 130°C. 18 reached. Cover the beaker with a watch glass and elther transfer the solution to a conatant temperature apparatus or keep the solutlon warm, finally heating to just under boiling before use. If the solutlion 13 allowed to cool to approxi- mately 60°C., recrystallizatlon of aluminum nitrate willl take place. It is neceassary, therefore, to dllute the salting agent solutlon by about one third ln order to prevent recrystalllization 1f the solu- tion cools to room temperature. Accordingly, 1f the solutlon 18 to stand overnight, add 35 ml. of dlstlilled water per 100 ml. of salt- inz agent solutlion, mlx well, and cover. If the salting agent solutlon 1s. to be atored, the following procedure has been found convenlent. AdJjust the solutlon to the proper concentration (boiling poilnt, 130°C.) and tranafer to a 100- ml. three-necked reaction flask set on a heating mantle. AdJust the heating so that the temperature of the solutlon 1e kept at about 110°C. In one of the necks place a water condenser, in another neck a. thermometer, and Iin the third neck a removable ground-glass stop- 277 PROCEDURE, 6 (Continued) per. Thlse third neck 1s utilized for plpetting the ealting agent solutilon. | ATLUMINUM NITRATE WASH SOLUTION. Add 100 ml. of alumlnum nltrate salting solution (boiling point, 130°C.) to 73 ml. of distilled water and 4 ml. of concentrated niltric acid. Apparatus. Beckman DU spectrophotometer. Heating'mantle. . Three-necked reaction flask (1000 ml.). Water condenser. No. O rubber stoppers. Boil twlce 1n ethyl acétate before use. Sixty-milliliter separatory funnels (Squibb, pear-shaped). Procedure Sample Dissolution. Place an appropriate quantity (1 to 5 grams) of the sample in a tared welghing bottle, stopper the bottle, and welgh the bottle and contents immediately. Carry out a molature determination on a separate sample 1f uranilum 1s to be calculated on a dpy welght basis. Bring the sample into solutlon iIn one of three ways: (1) nitric acid treatment, (2) multiacid treatment, or (3) sugar carbon-godium peroxide fusion. For the nltric acld tfeatment, dlssolve the sample in a sultable quantity of nltric acld and transfer the solution and insoluble resldue into an appropriate volumetric flask and make up to volume. Regulate the dllutlon so that the aliquot chosen for extractlion will contaln between 10 and 30 mg. of uranium oxlde if the final dllutlon for the colorimetric finish is to be 250 ml. AdJjust the acldlty of the sample solution to about 5% in nitric acid. | If nitric scld treatment 1s not sufficient, treat the Sample wlth hydrochlorilc acld, nltrlc acid, perchloric acld, and finally sulfurle acid. If necessary, add a few mllliliters 278 PROCEDURE 6 (Continued) of hydrofluoric acld. Fume the sample to dryness and leach the resldue wilth nltrle aclid, finally transferring the solution and resldue to an appropriate volumetric flask and adjusting to 5% in nitric acld a8 in the glngle acld treatment. If the sample 1B refrgctory, use the sugar carbon-sodium peroxlde fusion method described by Muehlbergi. After dilssolu- tion of the sample 1n thls manner, transfer the acldified solu- tlon to an approprilate volumetrilc flask and dllute so that the final solutlon 1s 5% in nltrilc acid. Allquot solution samples dlrectly or dllute as required for an gkthyl acetate extraction. If the sample 18 aliquoted di- rectly for an extraetlon, add 5 drops of concentrated nitriec acild per 5-ml allquot of sample and standards before extraction. Where gamples are dlluted before aliquots are taken for extractlon, adjust the acidlty so that the final volume 1s 5% in nitric ecid. Ethyl Acetate Extractlon. Place an appropriate aliquot (usually 5 ml.) in a 60-ml. separatory funnel, the stopcock of which has been lubrlcated wlth sllicone grease. Add, by means of a graduated pipet, 6.5 ml. of alumlnum nitrate solutlon per 5 ml. of sample solutlon. The aluminum nitrate saltlng solu- tion should be added while hot (above 110°C.). Cool the solu- tlon to room temperature and add 20 ml. of ethyl acetate. Stopper the separatory funnels with pretreated rubber stoppers. Shake the mixture for U5 to 60 seconds. Occaslonally erystalll- ‘zatlion will take place In the separatory funnel near the stop- cock. In such a case place the lower part of the separatory funnel 1n a beaker of hot water untll the solidifled portion dissolves. After the layers have separated, draln off the aqueous (lower) layer. Occaslonally a cloudiness will appear at the boundary of the aqueous and organlc layer. Thls cloudy portlon should not be dralned off. Add 10 ml. of zlumlnum nitrate wash 279 PROCEDURE 6 (Continued) solution to the funnel and agaln shake the mixture for 45 to 60 seéonds. Draln off the aqueouB layer, once again belng careful to retaln the cloudy portion at the boundary In the funnel. Rinse Inslde the stem of the separatory funnel with a stream of water from a wash bottle. Water Stripplng of Uranlum from Ethyl Acetate Layer Followed by Sodium Hydroxlde=Hydrogen Peroxlde Colorimetric Finlsh. Add 15-ml. of water to the separatory funnel contalning the ethyl acetate, stopper the flask, and shake the mlixture for about 1 minute. After washlng off the stopper with water, drain the aqueous layer Ilnto a volumetrle flask of sultable slze and wash the Beparatory funnel and ethyl acetate layer 4 or 5 times with 5=ml. portlons of water by means of a wash bottle. Combine the aqueous fractions. Add enough 20% sodium hydroxide solution (w./v.) to neu- tralize the solution and dlssolve any preclpltated aluminum hydroxide, then add 10 ml. in excess per 100 ml. of final volume. Add 1 ml. of 30% hydrogen peroxide per 100 ml. of final volume and make up the volume to the mark wlth distilled water. Read the absorbahce after 20 minutes on the Beckman DU spectro= photometer at 370 mp agalnst a reagent blank, using l-cm. Corex cells and a ellt wldth of 0.2 mm. Compare the absorbances of the samples agalnst the absorbances of astandard uranium solu- tlons which ha#e been carriled through the procedure at the same time. Choose the standards so that they cover the range 1nto whlch fhe samples are expected to fall, using a ratio of one standard to six samples. In practlce 1t 18 customary to work between the limits of 10 and 30 mg. of uranlum oxide. This 1ia arranged by estlmating the requlred sample welghts and diluting and samplling accordingly. The final volume for colorimetric reading 1s usually 250 ml. 280 PROCEDURE 6 (Continued) Double Extraction of Uranium wlth Ethyl Acetate Followed by Appllcatlon of Differentlal Colorimetry. Urafiium determina- tions requiring the highest accuracy may be carrled out by a double extraction of uranium with ethyl aceftate followed by the applicatlon of differentilal colorlmetry as desoribed by Hiskey and o‘i:he::'Es.E:£ In such a case 1t 1ls recommended that between 100 and 150 mg. of uranium oxlde be extracted, and a wave length of 400 me be used durilng the colorimetric finish. The procedure described below has been found satisfactory. Extract an approprlate allquot of the sample solution with 20 mi. of ethyl acetate aB descrlibed above. Draw off the a- quecus layer into a second separatory funnel contalning 10 ml. of ethyl acetate. Stopper the funnels and shake the mlixture for 45 to 60 seconds. Draln off and discard the agueous layer. Add 10 ml. of aluminum nitrate wash solution to the flrst ethyl ace= tate extract, stopper, and shake the mlixture for 45 to 60 seconds. Drailn off the aqueous layer Into the separatory funnel containing the second ethyl acetate extract, stopper, and shake the mixture " for U5 to 60 seconds. Draln off and discard the aqueous layer. Combine the ethyl acetate fractions. Rinse the second separa- tory funnel wilth 20 ml. of water, dralning the washlngs 1lntc the separatory funnel containlng the comblned ethyl acetate frac- tions. Shake the mixture for 1 minute. Continue the water stripplng as descrlbed above, collectling the fractions 1n an approprlate volumetrlc flask. Finish colorlmetrlcally as de=- scribed previously, allowing the strongly colored solutlon to stand 1 to 2 hours to ensure stablllty before reading as a fading effect of about 0.005 absorbance (optical density) has some- times been noted on freshly prepared samples. Read the absorbance of the sample solution on the Beckman DU spectrophotometer at 400 mp agalnst a reference solutlon 281 PROCEDURE 6 (Continued) whilch containse a known amount of uranium end hfis been carried through the extractlon and color development procedure 1ln the same manner as the sample. Alao carry along other standards contalning slightly higher and lower amounts of uranlum than the sample. Determine the concentratlion of uranium in the aafiple elther by the callbration-curve method or the correction method, as described by Neal€. If the amount of uranium in the sample 1s not known, make a tesat run by taking an aliquot of the sample solutlon and assaylng for uranium by the more rapid sin- gle extractlion method. The standard solutlons to be used can then be chosen according to the result obtained. Removal of Interfering Thorium. After an ethyl acetate ex- traction, strlp the uranium Iin water from the ethyl acetate and collect the uranium fractlon 1n a 250-ml. beaker. Add snough | 20% (w./v.) sodium hydroxide solution to neutralize the solution and redissolve precipitdted aluminum hydroxlde. Then add 10- ml. excess of 20% sodium hydroxide solutlon and 1 ml. of 30% hydrogen peroxide per 100 ml. of final volume. Filtef the golu= tion through an ll-cm. 41H filter paper (Whatman), collecting the flltrate in a volumetrlc flask of sultable slze. Wash the paper and precilpltate once with 5 ml. of a solution of 2% sodium hydroxide contalning 0.1 ml. of 30% hydrogen peroxide. Re- dlssolve the preclpltate by washing the paper wlth 10 ml. of 10% nitric acld solution, collecting the washings 1n the original beaker. Neutrallze the solutlon with 20% sodium hydroxide solution, and add 2 ml. in excess. Add 0.5 ml. of 30% hydro- gen peroxlde, and filter off the precipltate on the origlnal filter paper, washing as before and collecting the filltrates in the original volumetric flask. If the precipltate on the paper 1s colored yellow, repeat thls step. Make the solution in the volumetrlc flask up to volume and read the absorbance 282 PROCEDURE 6 (Continued) on the spectrophotometer. Carry standards through the same procedure as the samples. 2 W. L. Muehlberg, Ind. Eng. Chem. 17, 690 (1925). o C. F. Hiskey, Anal. Chem. 21, 1440 (1949). lo C. F. Hliskey, J. Rabinowitz, and I. G. Young, Anal. Chem. 22, 1164 (1950). e G. Wo C. Mllner and A. A. Smales; Analyst 79, 414 (1954). | W, T. L. Neal, Analyst 79, 403 (195%). [ I. G. Young, C. F. Hiskey, Anal. Chem. 23, 506 (1951). PROCEDURE T7: Uranium-237. Source: B. Warren, LA-1721 (Rev) (1956). l. Introduction In the carrler-free method for the determlnation of U237, the principal decontamination step {which is preceded by a La(OH)3 scavenge and partlal removal of plutonlum as the cup- ferron complex) 18 the extraction of uranium into 30% TBP (tertiary butyl phosphate) in benzene. Addltlional decontam~ ination 18 effected by adsorptlon of uranlum, firgt on an anlon and then on a catlon exchange resin. The uranlum 1ls finally electroplated on platinum. The chemical yleld is 40 to 60% and 18 determined through the use of U233 tracer. The U237 18 BP-counted in a proportional counter with a 2.61—mg/cm2 Al abgorber, and from the number of counts the number of atoms of the lsotope 18 calculated. Four samples can be run in about 6 hours. 283 PROCEDURE 7 (Continued) 2. Reagentsa U233 tracer: amount determined by the c-countlng technlque employed La carrier: 10 mg La/ml [added as.La(N03)3 . 6320] Fe carrier: 10 mg Fe/ml [added as Fe(N03)3 + 9H,0 in very dilute HN03] HC1: 0.1M HC1: 5M HC1l: 10M HCl: conc. HNO3: 3M HNO: 5M HN03: conac. NH40H: conc. NH,OH - HCl: SM 2 (NH4)20204 in H,01 L TBP (teriary butyl phosphate): 30% by volume in benzene (Note 1) Aqueous cupferron reagent: 6% Methyl red indicator solution: 0.1% 1n 90% ethanol Methanol: anhydroue Chloroform NHE: gas 012: gas 3. Equipment Centrifuge Fisher burner Block for holdlng centrifuge tubes Pt-tipped tweezers Steam bath S5-ml syringe and tranafer plpets Mounting plates L 284 PROCEDURE 7 (Continued) 40-ml centrifuge tubes: Pyrex 8140 (three per aliquot of sample) Jon exchange columns: 8 om x 3 mm tublng attached to bottom of 15-ml centrifuge tube Anilon resin: 5 cm Dowex A2-X8, 400 mesh, (Note 2) Cation resin: 5 cm Dowex 50-X8, 100 to 200 mesh, (Note 2) Stlirring rods Motor-driven glass stirrers Plating set-up: same as that used 1n Procedure 1 except that the Pt cathode is a 1" dlsk and the glass chimney has a 7/8" 1.d4. 4, Procedure Step 1. To an aliquot of sample not exceeding 20 ml 1n a 30-ml 6entr1fuae tube, add 1 ml of U233 tracer and 3 drops of La carrier, and bubble 1n NH, gas untll the preclpltate which forms coagulates. Digest3for 15 min on a2 steam bath, centrifuge, and discard the supernate. Step 2. Diseolve the precipltate in 0.6 ml of conc. HCl and dilute to 10 ml with H,0. Add 5 drops of 5M NH,OH + HCl and 2 drops of Fe carrier (if this element 1s not already pre- sent), and allow to stand for 10 min. Add 4 ml of chloroform, 6 ml of 6% oupferron,land extract the Pu(IV)-cupferron complex by Btirring for 2 min. Remove the chloroform layer by means of a transfer plpet and diacard. Extract the aqueous phase. three addltlonal times with chloroform. To the aqueous layer 2add 3 drops of La carrier and bubble iIn NH3 gas until the pre- clpitate formed coagulates. Dlgest for 15 min on a steam bath, centrifuge, and dlscard the supernate. Step 3. Diseolve the precipitate in 1.6 ml of conc. HNOB, dilpte $0 5 ml with H20, add 2 ml of TBP solution, and stin for 2 min. Draw off the TBP layer and transfer to a clean 40- 285 PROCEDURE 7 (Continued) ml centrifuge tube. Extract again with 2 ml of TBP solution and comblne wilth the previous extract. Add 1 ml of TBP solu- tion to the original tube, draw it off, and comblne wlth the other extracts. Step 4, Wash the TBP extracts with two 3-ml portions of 5M HNO discarding the washings. Bubble 1n'Cl2 gas for 5 mln ’ at a vfgorous rate. Step 5. Tranefer the solution to a Dowex A2 anlon ex- change column. Permlt one-half of the solutlon to pass through the resin under 8 to 10 1lb pressure. Add 1 ml of conc. HC1l to the column and allow the remalnder of the solutlon to pass through under pressure. Wash the column twice with 2-1/2 ml of 10M ACl and then twice with 5M HC1l, dlscarding the washilngs. Elute the U with two 2=1/2-ml portlons of 0.1M HCl, catching the eluate 1n a clean 40-ml centrifuge tube. Step 6. Dilute the eluate to 10 ml with H,0 and pass through a Dowex 50 catlon exchange columm under 1 to 2 1b pressure. Wash the resin three times with 2-1/2-ml portions of 0.1M HCl and discard the washings. Elute the U wlth two 2-1/2-ml portions of 3M HNO3 into the plating cell. Step 7. Add 5 ml of 4% (NH4)20204, 3 drops of methyl red indicator solution, and make basic by the dropwlse addition of conec. NH40H. Make the solution Just red to the indilcator by the dropwise addition of 6M HN03, and add 3 drops 1ln ex- cess. Plate at 1.1 amp and 8 volts for 1% hr at 80°C, At the end of the flrst 10 min, add 3 drops of methyl red solution and make acld with 6M HNO Check acldity at two additional 3. 10-min intervals, and at the end of 40 min add 3 drops of cone. NH40H. At 10-min Intervale thereafter check to see that the plating solution 1ls Just baslc to the indlecator. Remove the cell from the water bath; wash three tlimes with methanol, 286 PROCEDURE 7 (Continued) and dismantle the cell, carefully keeping the Pt dlsk flat. Flame the disk over a burner. a-count the U233, mount, and B-count in & proportlonal counter wilth a 2.61-mg/cm2 Al ab=- sorber. Notes 1. The TBP is purified before use by washing first with 1M NaOH and then with 5M HN03. 2. Before use, both the anion and cation resin are washed alternately at least flve tlmes each wlth H20 and HC1, and are then stored in H20. 3. See Procedure 1 for the correctlon for le actlvity per mg U308 on plate. PROCEDURE 8: Radloassay of Uranium and Plutonium in Vegeta- tion, Soll and Water. Source: E. L. Gelger, Health Physics 1, 405 (1959). Abstract A method 1s dlscussed for the separation of uranium and plutonium from vegetatlon, soll and water. The method is based on the extractlion of uranium and plutonium from 4 to 6 N nitric acid into 50% tri-n-butyl phosphate in n-tetra=- decane dlluent. Uranlum and plutonlum are recovered together with sufficient reduction 1n total sollds to allow a-counting and pulse heilght analysis. Data from several hundred "spiked" gsamples to which uranium and plutonium were added 1ndlcate a nearly equal recovery of uranlum and plutonium. Average re- coveries are 76 * 14 per cent for vegetation, 76 + 16 per cent for soll, and 82 + 15 per cent for water. The procgdure 1s designed for samples that may be collected and analyzed 287 PROCEDURE 8 (Continued) for radloactivity as a part of a health physics reglonal monltoring program. Procedures Preparation of samples Vegetatlon. Cut oven-dried vegetatlon into small pleces and welgh 10.0 g into a 150 ml beaker. Heat the sample at 600°C, starting with a cold muffle furnace. When only white ash remalns, remove fthe beéker from the muffle furnace and allow to cool. Carefully add 2 ml of water, then add 10 ml of 8 N HN03—O.5 E_Al(N03)3 solution. Cover the beaker with a watch glase and boll the solutilon for 5 min. Allow to cool, add 1 ml of 2 M__KNO2 golutlon and transfer the sample to a 100 ml centrifuge tube. Use 4 fl_HN03 to complete the transfer. Centrifuge and decant the supernate lnto a 125 ml cylindrilcal geparatory funnel graduasted at 30 ml. Wash the residue with 4y N HN03, centrifuge, and decant the wash solutlon to the separatory funnel. The acid normality of the combined solu- tions at this point 1s 4-6 N and the total volume should not exceed 29 ml. Proceed to the extractlon procedure. Soll. Grind 5 g of oven-dried soll with a mortar and peatle untll the entlre sample ocan pase through a 200-mesh sleve. Welgh 1.0 g of the 200-mesh soll into a 50 ml platinum cruclble and heat the sample at 600°C for 4 hr. Remove the gample from the muffle furnace and allow to cool. Add 3 ml of T0% HNO3 and 10 ml of 48% HF then stir the sample for 2-3 min wlth a platlnum rod. Beat the sample 1ln a 200°C sand bath untlil all tracees of molsture are removed. Repeat thls HN03—HF treatment belng careful that the sample 18 completely dry before proceedling to the next step. Allow the sample to cool and then add 15 ml of 6 N HNO3-O.25 M Al(NO3)3 solution. Cover wlth a watch glass and heat 1n the sand bath for 5 miln. 288 PROCEDURE 8 (Continued) Allow to cool and decant the solution through a fllter, such as Whatman no. 40, into a 125 ml e¢ylindricel separatory funnel graduated at 30 ml. Leave as much of the resldue as possible in the orucible and repeat the hot 6 N HNO4-0.25 M Al(NO3)3 treatment. Allow to cool and then fllter. Proceed to the ex- traction procedure. | Water. Place 1 1. of the sample 1n a 1.5 1. beaker and 1if basic, neutralize with nitric acid. Add 15 ml of TO% HNO3 and evaporate to 30-40 ml. Decant the solution through a filter, such as Whatman no. 40, into a 100 ml beaker. Wash the 1.5 1. beaker, the residue and the filter with 4 N HNOB. Evaporate the combined solutlon in the 100 ml beaker to 5 ml. Add 20 ml of 4 N HNOB, cover with a watch glass, and heat for 5 min. Transfer the sample to a 125 ml cylindrical separatory funnel graduated at 30 ml. Wash the beaker with % g_HNO3 and transfer to the separatory funnel, belng careful that the total volume 1In the separatory funnel doea not exceed 29 ml. Proceed to the extractlon procedura. Extraction Add 1 .ml of 2 M KNO, to the sample in the 125 ml cyllndrilcal 2 geparatory funnel. Dilute to the 30 ml mark with 4 I‘_I_HNO3 and stir the solution briefly. Add 30 ml of 504 TBF in n-tetradecane. Agitate the solution vigorously for 4 min with an ailr-driven stlrrer. Discard the acid portion (lower layer). Wash the TBP portion with 4 Ij_.HNO3 and agaln dlscard the aclid portion. Back extract with seven 15 ml portions of distilled water, collecting the strilp solution 1n a 150 ml beaker. Evaporate the comblned aqueous portlons to 10-~15 ml, then quantitatlively transfer the solution to a flamed stalnless steel planchet. Allow to dry under a hest lamp, flame the plancfiet to burn off organlec residue, end count on an a-counter. Retaln for pulse-helght analysls 1f the a-count exceeds a speclfled level. 289 PROCEDURE 9: Separation of Uranlum by Solvent Extraction with Tril-n-octylphosphlne Oxlde. Source: C. A. Horton and J. C. White, Anal. Chem. 30, 1779 (1958). Abstract A slmple, rapld method for the determination of uranium in impure aqueous solutlons was developed. Uranium(VI) 1s extracted by 0.1M trl-n-octylphoaphine oxlde 1n cyeclohexane from a nitrie acid solutlion. A yellow color ls formed In an aligquot of the or- ganlc extract by additlon of dlbenzoylmethane and pyridine in ethyl alcohol. Interference by catlons 1s mlnlimized or eliminated by selectlive reduoction, by fluoride complexatlon, or by absorbance measurement at 416 mp rather than 405 mu, the wave length of maxlmum absorbance, Interference by excess fluorlde or phosphate 18 eliminated by addition of aluminum nitrate before extractlon. The range of the method 1ls 20 to 3000 ¢ of uranium ln the origlnal golution, and the standard deviatlon is +2%. Apparatus and Reagents Absorbance measurements were made with a Beckman DU gpectro- photometer;, using 1.00-cm. Corex or sllica cells. Phase equlllbration for moat extractions was carrilied out in the bottom portion of the apparatus (see accompanying figure). Phase separatlon and removal of allquots of the upper organic phage occurred after inverting the apparatus so that the solutlon was 1ln the portlon of thls apparatus shown on top 1n the figure. Some extractions were carrled out in 60- or 125-m]. separatory funnels. STANDARD URANIUM SOLUTIONS. A stock solutlon of 24.0 mg. of uranium(VI) per ml. was prepared by heating 7.10 gram of uranium (Iv-VI) oxide (U308), prepared from pure uranium(VI) oxide (UO3), in 10 ml. of perchloric acld to dlssolve 1t, and then dlluting the resultant solutlon to 250 ml. with water. Dilutions of this solution were made as required. Another standard sclutlon in 5% sulfurilc acld was also used 1In checklng the spectrophotometric callbration curve. 290 PROCEDURE 9 (Continued) DIBENZOYIMETHANE. A solutlon that contalned 1 gram of dibenzoylmethaene (1,3-diphenyl-1,3-propanedione), obtained from Eastman Kodak Co., in 100 ml. of 95% ethyl alcohol was prepared for use as the chromogenlc agent. PYRIDINE. For most of the work, a solution prepared by mlxing 1 volume of redilstllled reagent grade pyridine and 1 volume of 95% ethyl alcohol was used. TRI-n=-0CTYLPHOSPHINE OXIDE. A 0.10M solution of thls material, prepared 1in the authors! laboratory, 1n cyclohexane, Eastman 702 or 7025, was used. Thls phosphlne oxlde 1s now avallable commer- clally from Eastman (EK T440). Sodium bisulfite, 10 (w./v.} % in water, stored at about 10°C. Hydroxylamine sulfate, 2M 1n water. Potassium fluorlde, 1M in water, stored 1n a polyethylene bottle, Procedure Preliminary Treatment .A. Samples which do not contain inter- fering lons. Pipet a 0.5- to 8-ml. aliquot of a solution in nitric, perchloric, or sulfuric acld, estlmated to contain 15 to 2500 ¥y of uranium(VI), into the bottom portion of the extraction vessel. By the addltion of strong 10M sodlum hydroxide, nitric acld, or sodium nitrate, adjust the solutlon so that a total aqueous volume of 10 ml. will be 12 to 3N in hydrogen lon and 2 to 4M in nitrate ion. For almost neutral solutlens, 2 ml. of concentrated nitric acid wlll give the correct concentrations for a 10-ml. aqueocus- volume. AdJust the total volume to 10 ml. Up to 12 ml. of aqueous solution can be shaken with 5 or 10 ml. of extractant in the ap- paratus wlthout undue splashing. If the total aqueous volume i1s greater than 12 ml. after adJusting the acldlty and nitrate con- Ltent, perform the extractlon ln a separatory funnel instead of the speclal extractlon veasel. 291 PROCEDURE 9 (Contlnued) B. Semples containing ilron(III), chromlum(VI), or vana- dium(V). Pipet a 0.5- to 6-ml. aliquot of a solution in dilute perchloric or sulfurlc medlum, estlimated to contaln 15 to 2500 vy of uranium(VI), Into the bottom portlon of the extractlon vessel. Reduce the iron(III) to iron(II), the chromium(VI) to chromium(III), and the vanadium(V) to vapadium(IV or III) without reducing the uranium(VI) to uranium(IV). Sodium bisulfite 1s a satisfactory reductant 1f the solutlons are bolled to remove excess sulfur dloxlde. Hydroxylamlne sulfate is also a satlsfactory reductant, but amalgamated zinc 1s unsuitable. Add sufficlent nltriec acld or sodium nitrate and water so that the final agueous volume of 8 to 12 ml. wlll be 1 to 3N 1in hydrogen lon and 2 to 4M in nltrate ion. C. Samples contalning tiltanlum, thorlum, hafnium, zirconlum, or iron(III), but only traces of alumirmum. Plpet a 0.5- to 6-ml. aliguot of a solutlion in dilute niltrle, perchloric, or sulfurlo acld, estimated to contaln 15 to 2500 v of uranium, into the bottom of an extractlion vessel. Add sufficient base or acid, nltrate, end water to glve 2 volume of about 8 ml., such that the solution 18 1 to 3N in hydrogen ion and 2 to 4M in nitrate lons. Add up to e maxlmum of 2.5 ml. of 1M potasslum fluorlde when the concentra- tlons of interfering lons are unknown. If hligh concentrations of these lons are known to be present, additlional fluoride can be tolerated. D. Samples contalning excessive fluoride or phosphate. Pipet an allquot 1nto an extractlon vessel, and adjust the acld and nitrate contents aB in Treatment C. Add sufficlent aluminum nitrate to complex the fluoride and phosphate estimated to be present. The total volume should be 12 ml. or less. Extraction. For amounts of uranium estimated to be under about 1400 vy, pilpet 5 ml. of 0.1M tri-n-cctylphosphine oxlde in cyclohexane 1nto the extractlion veasel contalning the treated 292 PROCEDURE 9 (Continued) sample. For 1400 to 3000 v of uranlum, use 10 ml. of extractant. Attach the top of the vessel and shake for 10 minutee on a re= clprocating shaker. Invert the extractlion apparatus for separa- tlon of the phases and removal of allquots of the upper organic phase. 14mm. A T OS5 mm. "'_f $ 40/50 ‘f 67mm. _L ST EXTRACTION APPARATUS USED IN Procedure 9. - Color Development. Transfer by plpet a 1-, 2-, or 3-ml. aliquot of the organlc extract into a 10- or 25-ml. volumetric flask such that the final solutlon wlll contaln between 0.5 and 10 v of uranium per mi. For 10-ml., volumes, add 1.0 ml. of 50% 293 PROCEDURE 9 (Continued) pyridine in ethyl alcohol, 2 ml. of 1% (w./v.) % dibenzoylmethane in ethyl alcohol, and 95% ethyl alcohol to volume., For 25-ml. volumes, use 2.5 ml. of pyridine and 5 ml. of dlbenzoylmethane. After 5 or more minutes, measure the absorbance at 405 mp in l-om. cells, using 95% ethyl alecohol a8 a reference solution. For sam-~ ples recelving Treatment C, also measure the absorbance at 416 mu. A blank should be carrled through the enfire procedure dally. Calculate the uranium content using the factors obtalned by ex- tracting standard pure uranium solutlons as dlrected in Treatment A, and measured at both 405 and 416 mu. PROCEDURE 10: Radiochemlcal Determlnation of Uranium-237. Source: F. L. Moore and S. A. Reynolds, Anal. Chem. 31, 1080 (1959). Abstract A radiochemical method for the determinatlon of uranium-237 1s based on complexling the uranyl lon in alkaline sclution with hydroxylamine hydrochloride, followed by scavenglng wlith zlrconlum hydroxlde and extraction of the uranlum from hydrochlorle acld solutlon with trllsococtylamine-xylene. The technlque has been applled successfully to the determinatlon of uranlum-237 1ln homogeneous reactor fuel solutions. Preparation and 3tandardlzatlion of Uranlum Carrier Welgh ocut approximately 50 grams of uranyl nltrate hexshydrate. Dissolve and make to 1 liter with 2 M nitrilc acld. Standardize the carrier by plpetting 5-ml. alliquote into 50-ml. glase centrl- fuge conesa and preclpltating ammonium dluranate by addlng concen=- trated ammonium hydroxide. Fillter quantitatively through No. 42 Whatman fllter paper and lgnite 1ln porcelaln cruclbles at 800°cC. for 30 minutes. Welgh as U308. 294 PROCEDURE 10 .{Continued) Procedure In a 40-ml. tapered centrifuge tube add 1 ml. of uranium carrier and 0.2 ml. of zirconium carrier (approximately 10 mg. per ml. of zirconium) to a sultable aliquot of the sample solution. Dilute to approximately 10 ml., mlx well, afid precilpltate ammonium dluranate by the additlon of conecentrated ammonlum hydroxlde. Centrifuge for 2 minutes and dlscard the supernatant solutlon. Wash the precipltate once with 15 ml: of ammonium hydroxide (1 to 1). Dissolve the precipltate 1n 1 to 2 ml. of concentrated hydro- chloric acld solutlon, dllute to about 10 ml., add 1 ml. of hydroxylamine hydrochloride (5 M), and mix well. Precipitate zlreconium hydroxlde by the addltion of concentrated ammonilum hydroxide. Centrifuge for 2 minutes, add 0.2 ml. of zirconium carrler, and etlr the supernatant solution, belng careful not to disturb the precipltate. Centrifuge for 2 minutes. Add 0.2 ml. of zirconlum carrler and repsat. Transfer the supernatant solution to another 40-ml. centri- fuge tuve, add several drops of phenolphthaleln, and adjust the pH to approximately 8 by adding concentrated hydrochloric acid solution dropwlse. Add an equal volume of concentrated hydro=- chloric acid solutlon and extract for approximately 0.5 minute wltha one-half volume portion of 5% (w./v.) trilsooctylamine- xylene. Dilscard the aqueous phase. Wash the organlc phase by mixing for 0.5 minute with an equal volume portion of 5 M hydro- chloric acld solution. Repeat the wash step. Strip the uranium from the orgenlc phase by mlxlng thoroughly with an equal volume portion of 0.1 M hydrochlorie acld solution for 0.5 minute. Dlscard the organlc phase. Add 0.2 ml. of zirconlum carriler, mix well, and repeat the " above procedure, beginning with the precipltation of ammonium diuranate. 295 PROCEDURE 1C (Continued) Flnally, precipltate ammonlum dluranate by the addltion. of concentrated ammonium hydroxide. Centrifuge for 2 mlnutes. De- cant and discard the supernatant solution. Filter on No. 42 What- man fiiter paper and lgnite at 800°C. for 30 minutes. Weligh the ufanium-oxide on a tared aluminum foll (0.0009 inoh), fold, and place in a 10 x 75 mm. culture tube. Insert a sultable cork and count the uranium-237 gamma radloactivity in a well-type sclntillstlion counter. Count the same day of the last chemical separation. Apply a blank correction 1f very low uranium-237 levels are being determined. Determlne this correction by takling the pame aliquot of uranium carrier through the exact procedure described above. The blank correction 1s due primarily to the gamma radlo- actlivlity assoclated wilth the uranium-235 1n the uranlum carrier. PROCEDURE 11: Separatlion of Uranlum and Blsmuth. Source: A. Krishen and H. Frelser, Anal. Chem. 29, 288 (1957). Edltor'™a note: Uranlum has been geparated from a 5000=fold excess of bismuth by the followlng method. Uranlum is, however, not completely extracted (only 98.48% at pH values greater than 6.5). If this correction is applied, uranium 1s quantitatively detergined by polarographlic means withln an experlmental error of +1%, " Reagenta Acetylacetone. Commerclal acetylacetone was purilfied by the method described by Stelnbach and Freisercé Procedure Analysis. The method of Souchay and Faucherre,E-uaing 0.1M EDTA and 2M sodium acetate as a supporting electrolyte, was found to be suitable in the presence of dissolved acetylacetone. The half-wave potentlal was shifted to -0.47 volt but the wave helght . was not affected. 296 PROCEDURE 11 (Continued) Separatlon. Solutlions of uranyl sulfate contalning 0.1 and 1.0 mg. of uranium were mixgd with different amounts of bismuth trichloride solutlion. A solutlon of the dlsodium salt of EDTA was added to give a bismuth to EDTA ratio of 1 to 30. The pH of the mixture was ralsed to 7.5 by careful additlon of 1§Isod1um hydroxide. Then approximately 10 ml. of acetylacetone was added and the mix- ture shaken for 10 minutes. The acetylacetone phase was separated, filtered, and made up to a volume of 10 ml., of which 2 ml. was wlthdrawn by a plpet iInto a 10-ml, boroslllicate glass volumetric flask. The flask was very gently warmed untll the liquid was re- duced in volume to about 0.5 ml. Then the supporting electrolyte was added and the resulting solutlon deaerated for 5 minutes in a 10-ml, Lingane-Lalitlinen H-type polarographlc electrolysis cell. The polarogram was then recorded and the concentration of uranium found from sultable callbration curves. £ J. F, Steinbach, H. Freiser, Anal. Chem. 26, 375 (195%). b p, Souchay, J. Faucherre, Anal. Chim. Acta 3, 252 (1949). PROCEDURE 12: Isclatlon and Measurement of Uranlum at the Microgram Level. Source: C. L. Rulfs, A. K. De, and P. J. Elving, Anal. Chem. 28, 1139 (1956). Abstract A double cupferron separatlon of uranium using extractlon has been adapted to the mlcro level. Uranium(VI).does not extract in the first stage, which removee many potentially interfering elements. Uranium(IV), obtained in the residual aqueous solutlon by reduction at a mercury cathode, 18 simultaneously extracted as the cupferrate into ether, from which 1t can be re-extracted lnto 297 PROCEDURE 12 (Continued) nitric acid. A relatively simple one-plece glass apparatus is used for all operations. The uranlum recoverfi at the milligram level in an initisl 30-ml. sample wfia defiermined colorimetrically as 94%. ¥ith 0.03 to0 0.13 7 of radioactive uranium-233 tracer and 20 ¥ of natural uranium as carrier, the récovery is B86%; the latter includes the addltional step of electrodeposltion of the uranium onto a platinum planchet prilor to measurement by alpha counting, which 18 only 94% complete. The decontamination possible with this procedure was checked with 0.07 v quantities of uranlum- 233 in the presence of high mixed fisslon product activities; 85% recovery. was obtained, contelning only 0.9% of the fission product alpha activity (assumed to be uranium). Apparatus The reaction cell and simple eleotrical circult used 1s shown 1n the aocompanying figure. The electrolysls vessel, C, 18 protected from mercury lons diffusiné from the working reference calomel electrode, A, by a medium glase frit between B and C, and a fine frit backed with en agar plug between B and A, Between runs, cell C 13 kept filled wlth saturated potassium ohloride solution. The apparafus for the electrodeposlitlon of uranium onto platinum disks or planchets and for alpha-countlng measurement of the resulting uranium plates have been deseribed.£ Beta activity was measured by a chlorine-quenched argon=filled Gelger- RMuller counter (1.4 mg. per sq. cm. of window) with a Model 165 scaler; a scintillation well counter with a thallium-activated godium iodide erystal and a Model 162 scaler was used for gamma- activity measurement of solutions (ca. 5 ml.) contained in a 13 x 150 mm. test.tube. The scalers and counters are made by the Nuclear Inptrument and Chemlcal Corp. For examlnation of the gamma-rey spectrum, a gamma-ray sclntillation spectrometer (bullt 298 PROCEDURE 12 (Continued) | in the Department of Chemlstry, University of Michigan) was used through the courteasy of W. Wayne Melnke. Reggents All chemlcals used were of C.P. or reagent grade unless otherwise speclfied. The ethereal cupferron solution used (200 to 300 mg. of cupferron per 50 ml.) was actually a hydrogen oup- ferrate solution; the ether and cupferron were mixed ln s mixing eylinder with 5 to 10 ml. of 10 to 20% sulfuric acid and shaken until dissolution was complete. Procedures Reductlve Extractlon. At the commencement of a run, bhrildge B 18 flushed through stopcock 2 by filling B with fresh potasslum chloride solution from the funnel through 1. € is dralined and rinsed; 1 18 left open for a time to flush the frit. With 3 cloeed, 4 to 5 ml. of triple-distlilled mercury 1s placed in C. About 30 ml. of uranyl sulfate solution (0.5 to 5 mg. of uranium and 0.5 to 1.5% in sulfuric acld) is added and a potential of -0.35 volt vs. S.C.E. 18 applled to the mercury. About 15 to 20 ml. of the ether cupferron solution lg added. Stirring 1s adjusted at Just over the minimal rate for efficlent current flow (usually about 0.2 ma. flows without stirring and 1.2 to 2.6 ma. with stirring). Stopcock 1 is opened for about 30 seconds at approximately S-minute .intervals throughout the run to minimlze any loss of uranium into the bridge. A% 15- or 20-minute intervals, stirring 18 interrupted, the ether extract 1s bled through stopcock 4 into cell D, and 15 to 20 ml. of fresh ether-cupferron solution 1s added. Runs of 40- to 55-minute total duration appear %o be adequate. Three increments of ether-cupferron solutlon were usually used, ' followed by a 5= to 10-ml. pure ether rinse at the conclusion of “the run. (See Note 1.) 299 PROCEDURE 12 (Continued) Stirrer O SR Potentio- meter | % 5ma‘.- ELECTRICAL CIRCUIT FOR ELECTROGCHEMICAL REDUGCTION OF URANIUM FOR Procedure 12. Extraction and Measurement at Microgram Uranium Level. A gslution of uranium-233 (10'7 to 10'8 gram) together with about 20 v of natural uranium (as sulfate) was submitted to reductive extraction with cupferron for about 50 to 60 minutes. The uranium (IV/III) cupferrate was then re-extracted in cell D from the ether solution into three sucecesslve 15-ml. porti,onia’of ™ 300 PROCEDURE 12 (Continued) nitric acld. The comblned nltrilc acld extract was evaporated to about 5 ml., treated with 25 to 30 ml. of concentrated nitric and 2 ml. of perchloric acid, and then evaporated to dryness. The residue was digested with 10 ml. of 0.1M nitric acid for a few minutes; the solutlon obtalned, after addition of about 10 vy more of natural uranium (as sulfate), was used for electrodeposition of the uranium onto a platinum planchet from an oxalate medium.2 A windowlees flow counter wlth Q-gas was used for counting the alpha emisslon from the electrodeposited uranium.2 The whole operation took about 4 to 5 hours. Each méasure- ment of alphas from the samples was callbrated by counting a uranium oxlide standard (Natlonal Bureau of Standards No. 836-5). Note 1. In some rune the current dropped to a low level soon after the requisite number of eoulombs had passed for about a 3- electron reduction of the uranium present. In other cases, the current dld not deorease, but dlscontinuance of the run beyond any pcint where twlce the theoretical ourrent had passed gave patisefactory uranium recovery. In the latter cases, a gray ether- insoluble, but alcohol=-soluble precipltate (apparently a merocury cupferrate), was usually evident in the agueous phase. The cur= rent efflclericy for the deslred process appeared to be good 1n most runs. The comblned ether extracts may be re=sxtracted 1ln cell D by lnserting a clean stirrer, or they may be tranaferred witfl.rinsing into a ¢lean separatory funnel. Three extractions with 20 to 30 ml. each of 0.5M, 4M; and 0.5M nitric acld were adequate to re- extract uranium into aqueous sclution. 2 0. L. Rulfs, A. K. De, P. J. Elving, J. Electrochem. Soac. 10%, 80 {1957)- 301 PROCEDURE 13: The Determination of Uranhium by Solvent Extraction. Source: R. F. Clayton, W. H. Hardwick, M. Moreton-Smith and R. Todd, Analyst 83, 13 (1958). Abstrect The development of solvent-extraotlon methods for deter- mining trace amounts of uranium-233 in 1rradiated thorium is described. Thorium and 1ts alpha-emitting daughters are com- pPlexed with EDTA, and, when uranium-233 ls extracted as 1ts di- ethyldithleocarbamate complex, only blsmuth-212 accompanies 1it. This 1s Immaterlal for colorimetrie or fluorimetric finlshes, but, for determlnation of the uranium-233 by alpha counting, the bismuth~212 must first be allowed to decay. If, however, the uranium-233 1p extracted gs 1ts 8-hydroxyquinoline ocomplex, no alpha emitter accompanles 1t and concentratlions of uranlum-233 ranging from 100 pg per ml down to 0.0l ug per ml in 0.7 M thorium solutlon have been determined in this way. METHOD FOR DETERMINING URANIUM-233 IN THORIUM NITRATE SOLUTIONS BY EXTHACTION WITH OXINE REAGENTS =~ Oxine solution A--A 10 per cent w/v solution of B-hydroxj- qulnoline in isobutyl methyl ketone. Oxline solution B--A 2.5 per cent w/v solution of 8-hydroxy- quinoline 1n lsobutyl methyl ketone, EDTA solutlon-~Dissolve 372.9 g of the disodium salt of ethylenedlaminetetra-~acetic acid in 500 ml of water containing 80 g of sodium hydroxlide and make up to 1 1liter. lml 323 mg of thorium. Nitric aold, N. Ammonia solution, sp. gr. 0.880. Ammonla solutlon, 0.2 N. Bromothymol blue indleator solution. Anti-creeping solution--A 20 per cent solution of ammonlum 302 PROCEDURE 13 (Continued) chloride contalning 2 per cent of a water-soluble glue (Stephen's Stefix was found to be sultable). PROCEDURE FOR 0.01 TO 1 pg OF URANIUM-233 PER ml-- With a plpette place a sultable volume of sample solution, containing not more than 600 mg of thorium, in a 40-ml centrifuge tube fitted with a8 glass stirrer. Add EDTA esolution to give about a 10 per cent excess over the thorlum equivalent and then add 3 drops of bromothymol blue indlcator solution. Add ammonia solution, sp. gr. 0.880, until the indiocator turns blue. Return the color of the indicator to yellow by adding. N nitric acid and then add 0.2 N ammonia solutlon until the color of the indicator Just turns back to blue (pH 7). Add 2 ml of oxine solution A, stir for 5 minutes, s8pln in a centrifuge to separate the phases and then stopper the tube. Evaporate duplicate 0.25-ml portions of the solvent phase slowly on stalnless-ateel counting trays that have had 1 drop of anti-creeping solutlon evaporated at their centers.®2 Heat the trays to redness 1n the flame of a Meker burner, cool and count. PROCEDURE FOR 1 TC 100 ug OF URANIUM-233 PER ml-- With & pilpette place a sultable volume of sample solutlon, contalning about 10 pg of uranium-233, 1nla 40-ml centrifuge tube and dilute to 3 ml with water. Add EDTA solution to give a 10 per cent excesas over fthe thorium_equivalent. Add 2 drops of bromothymol blue indlcator solution and edjust the pH to 7 as previously descrilbed. Add 5 ml of oxline solution B, stir for 5 minutes, spin in a centrifuge to separate the phases and then stopper the tube. Evahofate duplicate 0.1 or 0.25-ml portlons of the solvent phase for cofinting, as before. Note that for a fluorimetric finlsh to elther procedure, sultable dupllicate portlions of the solvent phase should be 303 PROCEDURE 13 (Continued) avaporated in platinum fluorlmeter dlshes before fuslon with sodium fluoride. METHOD FOR DETERMINING URANIUM-233 IN THORIUM NITRATE SOLUTIONS BY EXTRACTION WITH SODIUM DIETHYLDITHIOCARBAMATE REAGENTS-- Hexone. Sodlum dlethyldithlocarbamate solutlon--A freshly prepared and filtered 20 per cent w/v aqueous solution. EDTA solution--Prepared as described in reagents list, p. 377. Ammonium nitrate solution, 2 M . Ammonia solution, sp. gr. 6.880. Nltric acid, concentrated and N. Screened methyl orange 1lndicator solutlon. Antl-creepling solution--A 20 per cent solution of ammonium chlorlde contalning 1 per cent of a water=soluble glue. PROCEDURE FOR 1 TO 100 pg OF URANIUM-233 PER ml-- With a plpette place a suitable volume of sample solution, containing about 10 ug of uranium-233, in a2 40-ml centrifuge tube fitted with a glass stirrer. Dillute to 4-ml with 2 M ammonlum nltrate and add EDTA solutlon to glve a 10 per cent excess over the thorlium equivalent. Stir and make Just alkaline to screened methyl orange by adding ammonls solution and then add 0.5 ml of sodlium dlethyldlthiocarbamate solutlon. Stir and add N nitric acid untll the solution is mauve (not red). Add 5 ml of hexone, stlr for 5 minutes and add more acild to maintaln the mauve color 1f necessary. Spln 1n a centrifuge to separate the phases and then stopper the tube. Evaporate sultable duplicate portions of the solvent phase on stalnless=-eteel counting trays that have had 1 drop of anti- creeping solutlon evaporated at thelr centers. Heat the trays to redness in the flame of a Meker burner, allow the bismuth-212 304 PROCEDURE 13 (Contilnued) to decay, and then count. Alternatively, for a fluorimetrilec finish, evaporate duplicate portione of the solvent phase in platin- um fluorimeter dishes for fuslon with sodlum fluorilde. Note that greater sensltivity can be obtalned by starting wlth a larger volume of sample or by evaporating larger portlons of the solvent phase. 2 w. H. Hardwick, M. Moreton-Smith, Analyst 83, 9 (1958). PROCEDURE 14:; Uranium Radiochefiical Procedure Used at the Unlverslty of Californla Radlation Laboratory at Iilvermore. Source: E. K. Hulet, UCRL-4377 (195%4). 12 Atoms of U237 1solated from a 3-day- 14 Decontamlnation: 3 x 10 0ld mixture contalning 10" fisslone showed no evldence of contamination when decay was followed through three half lilves. Yleld: 30 to 50 percent. Separation time: About four hours. Reagents: Dowex A-1 resin (fall rate of 5=-30 em/min). Zinc dust, lsopropyl ether. 2M Mg(N03)2 with 1M HNO,. 2M HC1 with 2M HF. l. To the solution contalning the activity in HCl in an Erlen- meyer flask, add uranlum tracer in HC1l, 1 ml of conc. formlc acld and several ml of conc. HCl. 2. Boil gently until volume 1s ~2-3 ml, replenishing the solu- tion with several ml of formlc acld during the bolling. 3. Transfer to 20-ml Lusterold centrifuge cone, rinsing flask twice with 1-2 ml of water and add 2-3 mg of La*tT. add 1 ml of conc. HF, gtir, heat, and centrifuge. 305 g. 10, PROCEDURE 14 (Continued)} Transefer supernatant to 20-ml Lusterold centrifuge cone, add 2=3 mg La+++, stir, heat, and centrifuge. Transfer supernatant to 20-ml Lusteroid, add 5-10 mg Lat'T, 1/2 m1 of ceonoc. HCl and heat in a water bath. When the solu- tion 1s hot, add small portions of zinc dust and stir. About three small addltions of zinc duat should be made over a half- hour perlod wlth vigorous stirring after each addition. If the zinc dust tends to ball and sink to the bottom of the tube at any tlme, addition of more conec. HCl wlll solve thils problem. When all the zine from the last addition has dissolved, add 4 or 5 ml of water and lfimi of conc. HF. 8tir, cool, and centrifuge, retalning the LaF3 precipitate. Wash.precipitate with 2 ml of 2M HC1l + 2M HF. Dissolve the precipitate with 6M HNO, saturated with H3BOg, stirring and heating. Trangfer the solutlon to a 40-ml glass centrlfuge cone, washlng out the Lusterold cone with water. Add several drops of H202 and etir and heat. Add 2 mg Fe+++ and make solutlon baslec with NHAQH and some NaOH. Heat, stir, and céntrifuge.. Wash the precipltate with 2 ml of water. Dissolve the precipltate 1in one to two drops of econe. HNO3 and heat. Cool, add 10 ml QE_HQ(NOB)e + 1M HNOg saturated with ether. Equillbrate twlce with 10-15 ml of dllsopropyl ether. Pipet the ether phase into a clean 40-ml cone and equilibrate ether layer with 3 ml of com. HCl. Pipet off and discard ether layer. Heat HCl for ~30 seconds and again pipet off the ether layer. Pass the HCl solution through a Dowex~l anlon resin bed (2 ‘em x 3 mm) by pushing the solution through the column with air pressure. Rinse the centrifuge tube once with 1 ml of conc. HC1 and push this solution through the column. Wash resin with ~1 ml of conc. HCl. Discard effluent. 306 PROCEDURE 14 (Continued) 11. To colurm, add ~3/4 ml of O.5M HCl. Collect the eluate and evaporate to a small volume and plate on a platinum dlsc. PROCEDURE 15: Use of Ion Exchange Resins for the Determinatilon of Uranlum 1in Ores and Solutlons. Source. 8. Fisher and R. Kunin, Anal. Chem. 29, %00 (195T). Abstract The separation of uranlum from the lons interferlng wlth 1ts analysls 1s accomplished by the adsorptlion of the uranium(VI) sul- fate complex on a quaternary ammonium anion exchange resin._ Intef- ference of such lons &8 1ron(III) and vanadium(V) is avolded by thelr preferentlal reduction wlth sulfurous acid so that they, as well a8 other cations, are not retained by the resin., Uranium is eluted for analysls by dllute perchlorilic acid. The methed is applicabie to both solutlons and ores. Ore Solutlon Two methods for the opening of_uranium-bearing ores were investigated in conJunction with the lon exchange separatlion. The flret 1s the standard digestlon wlth hydrofluoric and nltrlc aclds, with subsequent evaporatlon to dryneass followed by a sodium car- bonate fusion.2 The carbonate melt 1s dissolved in 5% sulfuric acld to form a solution for the separation. A second method for routine enalysls, designed to eliminate the need for hood facili- tles and platinum vessels; lnvelves an oxldatlive leach with an acidic manganese(IV) oxlde syatem. This procedure 18 given in detail below. Other workersE, using the auvthors' separation procedure, have recommended solutlon of the ore by treatment with 12M hydrochloric aclid plus 162 nitric acld followed by fuming' 307 PROCEDURE 15 (Continued) wilth sulfurlce aecld to produce a sultable uranium solution for the column influent. Procedure. Welgh out samples of ore estimated to contaln an amount of uranium oxlde less than 100 mg. but sufficient to be detected by the chosen method of analysis. Add 20 ml. of 20% by volume sulfuric acid and 2 grams of manganese(IV) oxide. Heat the mixture to bolling. Allow to cool to room temperature. Dilute with approximately 50 ml. of water. AdJust to a pH between 1.0 and 1.5 by the dropwlss addition of 20% sodium hydroxide. Filter through fine-pore filter paper using two 10;m1. portions of water to wash the residue on the paper. Ton Exchange Separation Apparatus. Tubes 0.5 inch in dlameter with high-porosity sintered glass fllter disks fused to the lower end are used to contaln the resin, The rafte of flow of solutlons through the tube 18 regulated by a Bcrew elamp on rubber tubing below the filter. Small separatory funnels are attached to the top of the column to feed the sample and reagents. Procedure. Convert a portion of quaternary ammonium anion exchange resin (Amberlite XE-117, Type 2) of mesh size %0 to 60 {U.S. soreene) to the sulfate form by treating a column of it with IQ% sulfurio acld, using 3 volumes per volume of resln. Rinse the acld=treated resin with delonigzed water until the effluent 1s neutral to methyl red. Draln the resin so prepared free of excess water and store 1n a bottle. A 5-ml. portion of thils resin 1s used for a single analysls. The resln 1s loaded into the filter tube and the bed so formed 18 backwashed with enough water to free 1t of alr. After the resln has settled the excess water is drained off to within 1 cm. of the top of the bed prior to the passage of the sample through the bed. Add 5 drops of 0.1% methylene blue to the partially neu- 308 PROCEDURE 15 (Continued) tralized (pH 1.0 to 1l.5) solution from the dissolved sodium car- bonate melt or from the flltered manganese(IV) oxide leach. Add 6% sulfurous acid dropwise until the methylene blue is decolorized and then add a 5-ml. excesB. Pass the reduced sample through the resin bed at a rate not exceeding 2 ml. per minute. Wash the sam- ple contalner with two 10-ml. portions of water, passing the washing through the resih bed at the same flow rate. Elute the uranium with 50 ml. of 1M perchloric acid. Determlne the uranium content of the perchlorioc acld fractlon colorlimetrically by the standard sodium hydroxide-hydrogen peroxide methodZ o# volumetri- callyg. For colorlimetric analysis standard uranium solutlons containing perchloric acld should be used 1n establishing the qurve. 2 p. S. Grimaldl, I. May, M. H. Fletcher, J. Titcomb, U. S. Gecl. Survey Bull. 1006 (195%). D H. 7. Seim, R. J. Morris, D. W. Prew, U. 8. Atomic Energy Comm. Document UN-TR-5 (1956). £ 0. J. Rodden, "Analytical Chemistry of the Manhattan Project,” McGraw-H11l, New York, 1950. PROCEDURE 16: The Use of a "Compound" Column of Alumina and Cellulose for the Determlnation of Uranium in Minerals and Ores Containing Arsenlc and Molybdenum. Souroce: W. Ryan and A. F. Willieme, Analyst 77, 293 (1952). Abstract A technlque 1n inorganic chromatogrephy, with alumina and cellulose adsorbents 1ln the same extraotion column, 1s described for the separation of uranium from minerals and orea. The pur- pose of the alumina 1s to retain arsenic and molybdenum, which 309 PROCEDURE 16 (Continued) are not readlly retalned by cellulose alone when ether containing 5 per cent v/v of concentrated nitric acid, sp.gr. 1.42, 18 used as the extraction solvent. METHOD FOR SAMPLES CONTAINING MOLYBDENUM OR ARSENIC OR BO'TH Solvent--Add 5 ml of concentrated nitrlec acld, sp.gr« 1.42, to each 95 ml of ether. PREFARATION OF ALUMINA-CELLULOSE COLUMN-- The adsorptlon tube for the praparation.of the colum 1z a glass tube about 25 cm long and 1.8 em in dlameter. The upper end 18 flared to a dlameter of gbout 8 em to form a funnel that permlts easy transfer of the sample. The lower end terminates in a short length of narrow tubling and 1ls closed by a short length of polyvinyl chloride tublng carrylng a screw cllip. The inslde surface of the glass tube 1s coated wlth a slllicone in the manner described by Burstall and Wells.2 Welgh 5 or 6 g of cellulose pulp* into a stoppered flask and cover 1t with ether-nltric acld solvent. Pour the suspenslon ln- to the glass tube, agltate gently and then gently press'down-the cellulose to form a homogeneocus column. Wash the column wlth about 100 ml of ether-nltric acld solvent and finally allow the level of the solvent to fall to the top of the cellulose. Next pour about 15 g of activated alumintum oxide* on top of the cellulose, pour on 30 ml of ether-nlitric acld solvent and vig- orously agilitate the alumina with a glass plunger. Allow the packing to settle.. Allow the level of the ether to fall to the surface of the alumina and the column 1s ready for use. * Whatman's Standard Grade cellulose powder 1ls sultable. t Type H, Chromatographic Alumina, 200 mesh. Supplled by Peter Spence Ltd. 310 PROCEDURE 16 (Continued) PREPARATION OF SAMPLE SOLUTION FROM MINERAL OR ORE=- Welgh 1nto a platinum dish sufficlent of the sample to gilve 100 to 150 mg of U303, which 1s a convenient amount for a volu- metric determinatlon. Decompose the sample by treatment with nitric and hydrofluoric aclds in the manner describaed by Burstall and Wells.® Finally remove hydrofluoric acid by repeated evapora- tilons with nitrlc acld and take the sample to dryness. If the addition of dilute nitrlc acid indicates the presence of undecom- poeed materlal, fllter the insoluble residue on to a filter-paper and ignite and fuse 1t 1In a nickel orucible with a few pellets of potasslium hydroxide. Then add the melt to the filtrate and take the whole to dryness. Add 4 ml of diluted nitric aecid, 25 per cent v/v, to the dry residue, gently warm to dlssolve the mixture and then ecol the solution, which 1s then ready for chromatography. EXTRACTION OF URANIUM— Transfer the sample on a wad of dry cellulose pulp to the top of the prepared alumina-aellulose columm? and extract the uranium with 200 to 250 ml of ether-ni@ric acld solvent if ar- senlc or molybdenum and arsenle is present in the origlnal samplae. If molybdenum alone 18 present, the amount of solvent can he reduced to 150 ml. Screen the column from direot sunlight. After removal of ether from the eluate, determine the uranium volume- trically. 2l 2 F. H. Buretall, R. A. Wells, Analyst 76, 396 (1951). D p. H. Burstall, A. P. Williems, "Handbook of Chemical Methods for the Determination of Uranium in Minerals and Ores," H. M. Stetlonery Office, London, 1950. 311 PROCEDURE 17: Determination of Uranium-235 1n Mixtures of Naturally Occurring Uranlum Isotopes by Radioactivation. Source: A. P. Seyfang and A. A. Smales, Analyst 78, 394% (1953). Abstract A method previously used® for determlning uranlum in mlnerals by neutron irradiation followed by measurement of the separated fisslon-product barium has been extended to the determination of uranium-235 in admixture with uranium-234 and uranium-238. With microgram amounts of uranium-235, short irradlations in the Harwell plle glve ample Bensitivity. Preclsion and accuracy of better than +2 per cent have been achleved for a range of uranium-235 contents covered by a factor of more than 10°. | Method REAGENTS -= Magnesium oxlde--Analytical reagent grade. Nitric acid, sp. gr. l.42. Barium chloride solution--Dissolve 18 g of BaCl,-2H,0 in water find malkte up toc 500 ml. Lanthamum nitrate solution--A 1 per cent w/v solution of .La(N03)'3 °6H20. ' | Ammonium hydroxide, sp. gr. 0.880. Strontium carbonate solution--A 2 per cent w/v solution. Hydrochlorlc acld-diethyl ether reagent--A mixture of 5 parts of concentrated hydrochloric aeid, sp. gr. 1.18, and 1 part of dlethyl ether. Sodium tellurate solution--A 0.4 per cent w/v solution. Zine metal powder. Methyl orange lndloator. Potassium lodide solution~-A 1 per cent w/v solution. Sodlum hypochlorite sclutlion--A commercilal aoiution containling 10 per cent of avallsble chlorine. 312 " about 50 mg of U PROCEDURE 17 (Continued) Hydroxylamlne hydrochloride.. _ Ferrile chloride solutlon--A 1 per cent w/v solution. Sulfuriec acid--A 20 per cent v/v solutilon. IRRADIATION-- Solids-- Samples contalnlng not much more uranium-éjs than natural urgnium (say, up to three times more or 2 per cent) may be Ilrradiated as polld; thils 1s usually U308° For these cut a B=cm length of 2-mm polythene tubing and seal one end bylwarming and pressing. Introduce freshly lgnited analytical reagent grade magnesium oxlde to form a compact layer 4 to 5 mm in helght at the sealed end of thé tube. Welgh the tube and contents, add 308 and re-welgh. Add a further simllar layer of magneslum oxide on top of the U3°8 and then seal the open end. Leave a free space about 1 cm long between the top of the mag- nesium oxlde layer and the seal, for ease of opening. Treat standard aend samples similarly. Place the tubes elther 1n.a "special polythene bottle for irradilation in the pneumatic "rabbit" of the pille or in a 3-inch aluminum can for irradiation 1n'£he Yaself-perve"” holes in the pille. Irradiation 1s carried out for any requlred time; usually 1t is about. .5 minutes. After irra- dlating, place the contalners in lead shleldlng for about 15 hours. After thie perlod, tap down the ocontents of the polythene tube away from one end and carefully ocut off the top. Empty the contents into & 50-ml centrifuge tube. (The plug of magnesium oxlde serves to "rinee” the sample tube as it ls emptied.) Add 2 ml of concentrated nitric acid (sp.gr. 1.42), gently warm to "dissolve, and finally boll off the nltroue fumes. Add 5.00-m1 of a barium solution to act as carrier (a solution of 18 g of barium chloride, BaCl,*2H,;0, in 500 ml of water). Ligulds--For more hlghly enriehgd samples or when the amognt -of sample avallable 1s small, solutions contalning welghed 313 PROCEDURE 17 (Continued) quantitlies of solld sample must he lrradiated 1n small sillica ampoules. The ampoules, whlch have a capaclty of about 1 ml, are prepared from sillica tubing. After one end of each has been sealed, the ampdules are welghed, the sample solution added from a flne-pointed glass dropplng-tube and the ampoules re-welghed. Pack the ampoules, after sealing the open ends, 1in cotton wool 1n a 3-inch aluminium can and irradiate them in the "self-serve" posltlon of the plle. The time of lrradlation necessary can be calculated from the usual activation formulé; as an example, 1 pg of uranium-235 irradiated for 24 hours 1n a flux of 1012 neu- trones per sq. cm per second glves about 5000 counts per minute of barium-140 at 5 per cent counting efficlency, 24 hours after the 1rradiation. After removing them from the pile,'place the samples and gptandards in lead shlelding for about 15 hours; the maln actlvity 1s due to silicon-31l. Transfer the ampoules to 100-ml tall-form beakers contalning a few milliliters of water and 5.00 ml of barlum carrier solutlon, carefully break off both ends of each ampoule and warm to ensure thorough mixing. Decant into centrl- fuge tubes and wash out the ampoules and beakers with further small portions of water. CHEMICAL SEPARATION-- Evaporate the solutlon contalning the lrradlated uranium and barium carrier to 5 to 6 ml and add two drops of 1 per cent lanthanum nltrate solution. Warm 1f necessary to dilssolve any barium nitrate that may have crystallized, add concentrated ammonium hydroxlde dropwlse untll a permanent preclpltate 1s obtalned and then two drops 1n excess. Centrifuge and decant Into another centrlfuge tube. Add methyl orange indlecator, and then hydrochloric acid-until the solutlon 18 acid. Add 2 drops of 2 per cent strontium solutlon, about 25 ml of hydrochloric 314 PROCEDURE 17 (Continued) acid - dlethyl ether reagent, mix thoroughly, centrifuge and decant. Wash the preciplitate with 5 ml of reagent, centrifuge and decant. Disgolve the barium chloride precipitate in 3 to % ml of water, re-preclpltate 1t by adding 20 ml of reagent, centri- fuge and decant. Wash with 5 ml of reagent, centrifuge and decant. Dlssolve the precilpltate in about 5 ml of water, add 6 drops of lanthanum solution and 6 drops of the 4 per cent tellurate solution and then about 3 mg of zlnc metal powder. When the effervescence ceases, make the éolution Just ammonlacal to methyl orange, centrifuge and decant into another tube. Add % drops of 1 per cent potasslum ilodlde solutlon and 2 drops of sodium hypo- chlorite solution. Warm and set aside for 2 minutes. Acldify wlth about 1 ml of hydrochloric acld, and add about 0.1l g of hydroxylamlne hydrochloride. Boll under & hoad until all the iodine appeare to be removed and the volume 1s reduced to 5 to 6 ml. Add 2 drops of strontlum solution and 2 drops of lanthanum solutlion and repeat thé double barlum chlorlde preclpltation and washlng, as above. Dissolve the precipitate in about 5 ml of water, add 6 drops of lanthanum solution, and 6 drops of 1 per cent ferrie chloride gsolution. Make ammonlacal to methyl orange, add half a crumbled Whatman accelerator tablet, and heat Just to bolling. 'Filter through a 7-cm Whatman No. 30 fllter-paper 1nto a centrifuge tube, wash twlce wlth 2 fo 3-ml portions of water. Dillute the flltrate to about 20 ml and meke slightly acld with hydrochlorlc acid. Heat nearly tc boiling and add dropwise 2 ml of 20 per cent v/v sulfuric acld. Allow the precipltate to settle, decant, wash with 10 ml of water, centrifuge, decant and repeat the washing procedure to complete removal of the excess of acld. Transfer ae mich as posslble of the preclpltate, by means of a dropplng tube and a few drops of water, to a tared aluminium 315 PROCEDURE 17 (Continued) counting tray. Dry under an infra-red lamp and finally heat in. 4 muffle furnace at 500°C for 15 minutes. Cool, weigh and re- serve for counting. COUNTING TECHNIQUE-- ) The counting equipment for this work consists of (1) a power unilt (type 1082A or 200 is sultable), (11) scaling unit (type 200 or 1009B), (11i) time accessory unit {type 1003B), (1v) probe unit (type 200B or 1014A). Time pulses can be ob=- talned from a master elsotrlc clock serving several unlts. A mica end-window Geiger-Mfiller cgounter (2 mg per sg. cm.), of type EHM2, 18 suitable; 1t is mounted in a lead castle with a Perspex linlng and shelves. Check the counting equipment in the normal fashlon wlth a sultable beta-~emlttfer, such as natural uranlum oxide in equilib- rlum wlth UXl and sz. Place the sample to be counted 1In a Perspex carrler and insert it in a shelf at a Buifable distance from the Geigen-Mflller tube to attalin a counting rate of 2000 to 3000 counts per mlnute. Count for a sufflcient time to obtailn at least 10,000 counts for each barlum sulfate precipltate, counting the preclpltates one after another without undue delay. Correctlon for growth of lanthanum-l40 1s unnecessary if samples and standards are counted within, say, 60 minutes of each other provided the barium sulate precilpltatlons are carried out on each nearly simultaneocusly. CALCULATION OF RESULTS-- Correct all counts for background, colncldence loss and chemlcal yleld and express as the resulta in counts per minute. Welght of UP3° 1q standard _ Corrected count of standard Then 23;; - - Welght of U™~ 1in sample Corrected count of sample 35 and Welght °f“U2 in sample X 100 = percentage of uranlum-235 Weight of sample in sample., 8, = A. A. Smales, Analyst 77, T78 (1952). 316 PROCEDURE 18: Determination of Mlecrogram and Submicrogram Quantities of Uranium by Neutron Actlvation Analysls. Source: H. A. Mahlman end G. W. Ledlcotte, Anal. Chem. 27, 823 (1955). Abstract Miorogram and submlcrogram quantities of uranium have been determined in synthetlic samples, ores, and solls by neutron radloactivation analysis. The principles of the actlvation analysip method used in this determination and the processing of 1rrddlated samples are dlscussed. Thils method of analysis 18 a sensitive and specific method for determinling uranium 1in concen- trations as small as 0.1l ¥ per gram with a probable rélative standard error of 10#. Concentrations of uranium in quantities as small as 0.0001 ¥ per gram can be determined by neutron activ= atlor analysils. Radloactivatlion Analysis of Samples thgt Contaln Uranium Nuclear Irradiation of Sample. Welghed portions of the samples and the comparative standard are put into small quartz tubas. The tubems are closed with cork stoppers that are wrapped in gluminum. They are then irradlated in the reactor. After irradiation, the samples are allowed to decay about 4 hours and are then chemically processed as described below. The synthetle samples used 1in thls laboratory had been processed by a fllter paper partitlion chromatography technligue. After the separation, the paper was convenlently 1irradlated in short pleces of quartz tubing whoee openings were plugged by meana of cork stoppers. Chemlcal Separatlion of Neptunlum=-239. In most neutron activatlon analyses, é chemlcal separatlon 1s made to lsclate the radiocactivity of the element from all other radloactlve apecies in the sample. Usually an "isotople carrier"--a khown amount of the natural inactive element--13 added to the solutions 317 PROCEDURE 18 (Continued) of both the 1rradilated specimen and the comparison samples. The golutions are then processed chemlcally to lsolate the carrler and deslred radloelement from other elements and contamlnant radloactivitles. 3mall amounts of other elements are added as holdback or socavenging carrlers to asslst In the decontamlination process. Although neptunium-239 has a convenlent half l1life, 1t does not have a stable 1sotope that can be used a8 an'lsotoplc carriler. However, Seaborgi has shown that trace quantities of neptunium- 239 can be quantitatively carried on a nonlsotople carrler, such as cerilum. The method of analyals reported below uees lanthanum as a nonlsotoplc carrler for the neptunium-239 radiocactivity. (See Note 1.) Chemlcal Separation Procedure. PREPARATION. The lrradiated ore and soll specimens are dissolved by digestion in a mixture of concentrated nitric, hydrofluoric, perchloric, and sulfuric acids. (Additional hydrofluoric acid can be added 1f a residue of sllica remains 1n the bottom of the crucible.) After dissolu- tion, the sample 1s concentrated to heavy sulfuric acid fumes, cooled, and transferred to a 15-ml. centrifuge tube. If a residue (sulfate salts) remains after the transfer, the solutlon is cen- trifuged for 5 minutes, the supernatant transferred to another tube, and the resldue washed with 1 ml. of 1M nitrlc acid. The wash 1ls added to the supernatant and the residue discarded. (Centrifugation is always for the stipulated time and at full speed.) The sample 1s then further processed by the procedure reported herein. The irradiated synthetlc samples (paper chromstograms) are processed by carefully igniting the paper contained in a porcelain cruclble in a muffle furnace. The resildue 1s dilssolved in about 0.5 ml. of concentrated nitrlc acld. After dissolution, the 318 PROCEDURE 18 (Continued) sample 1s transferred to a 15-ml. centrifuge tube and the process- Ing continued wlth the procedure reported herein. PROCEDURE. Three (3.0} milligrams of lanthanum and 0.250 ml. of 5M hydroxylamine hydrochlorlde solutlon are added to the supernatant solutlon and the mixture digested for 5 mihutes wlth occaslonal stlrring. The solution is cautiously neutralized with concentrated ammonium hydroxlde to precipitate lanthanum hydroxide, after which the mixture 18 centrifuged and the supernatant liquid discarded. The precipltate of lanthanum hydroxide is dissolved in 2 ml. of 2M hydrochloric acld, and 1.0 mg. of strontlium (added as a solution of strontium niltrate to serve as a holdback or scavenglng carrier) and 0.250 ml. of 5M hydroxylamine hydrochloride solution are added to the solution. The solutlon ls agaln digested for 5 minutes wlith Ilntermittent stirring, and 0.200 ml. of concentrated hydrofluorlc acld 1s added dropwlse to the solutlon to precipiltate lanthanum fluoride. After centrlfugation, the supernatant liquild 1s discarded and the preclpitete washed wlth 0.5 ml. of 1M hydro- fluorie acld-1M nitric acld solution. After washlng, the lanthanum fluorlde precipltete ls dissolved ln 0.5 ml. of saturated borlc acld solution and 1.0 ml. of 6M nitriec acld. One (1.0) mllliliter each of 10% potassium perman- ganate solutlon and water are added to thlse solutlon, and the resulting mixture ls agltated well and digested for 5 minutea. Lanthanum fluoride 1s agaln precipltated wilth 0.250 ml. of con- centrated hydrofluoric acld; the solution 1ls centrifuged and the supernatant llquld transferred to another centrifuge tube. The preclpitate is washed with 0.5 ml. of 1M hydrofluoric acid-1M nitriec aclid solutlion and the wash comblined with the supernatant liquid. The preclpltate 1ls dlscarded. Three milligrams of lanthanum are added to the supernatant 319 PROCEDURE 18 (Continued) liquid, and the solutlon 18 digested for 5 minutes and ¢entrifuged. An additional 3.0 mg. of lanthanum are added to the supernatant 11quid and the solutlon agitated and digested for 5 minutes wilthout disturbing the first precipltate on the bottom of the tube; then the solution is centrifuged and the supernatant liquild transferred to another centrifuge tube. The preclpltate 138 washed with 0.5 ml. of 1M hydrofluoric acild-1M nitric acild solution; centrifuged, and the wash comblined wlth the supernatant liquid. The precipl- tate 1s discarded. One milligram of zirconium (added as a solution of zirconium nitrate to serve as a holdback or scavenglng carrier) and 0.250 ml. of 5M hydroxylamine hydrochloride are added to the solution and the mixture agitated and digested 5 minutes. Three (3.0) milli- grams of lanthanum and 2 ml. of 2M hydrofluoric acld are added to the solutilon, and the solutlion 1s digested for 20 minutes and then centrifuged. The supernatant liquid i1s dlecarded. The pre=- clpltate 1s washed with 0.5 ml. of 1M hydrofluorlc acid-1M nitric acld solution, and the resulting mlxture 1s centrifuged. The wash 8olution 1s dlscarded after the centrifugation. The precipitate 1s slurried in a small amount of 1M nitric acid (about 0.5 ml.) and transferred to a small borosilicate glass culture tube by means of a transfer pipet. The centrifuge cone 18 ringed wlth three 0.5-ml. portlions of 1M nitrie acld and the rinses transferred to the ceculture tube. The tube 1s stoppered wlth a cork stopper and the ¥ radiocesctivity measured by a well- type gamma scintlllatlon counter. The standard sample of uranium oxide (U308) is dissolved in nitric acld and an aliquot of the solution processed under the same condltions as the specimen samples. The uranium content of the sample 1n question 1s dqyermined by equating the ratio of the corrected neptunium-239 radioactlivity count in the unknown 320 . PROCEDURE 18 (Continued) and the corrected neptunium-239 radloactivity count in the standard sample. b 237 Note 1. Hamaguchl and co-workers— have used Np tracer to determine the chemlcal yleld.. 2 ga. T. Seaborg and co-workers, Metallurglcal ProJect Rept. CN- 2689,41 (Feb. 15, 1945) (classified). P-H. Hamaguchl, G. W. Reed, A. Turkevich, Geochlim. et Cosmochim. Acta 12, 337 (1957). Acknowledgements It 18 a pleasure to acknowledge the aselstance of Miss M. Tippet, Mliss R. Cushlng, Mr. N. 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Patent 2,897,047 (1959); NSA 14, 2501 (1960) . = 681. %. Aé)81otin, U. S. Patent 2,823,977 (1958); NSA 12, 10243 1958). 682. R. P. Larsen, Anal. Chem. 31, 545 (1959). 683. J. C. Warf, C. V. Banks, CC-2942 (1945). 68%. R. Fisher, CC-1057 (1943). 685. L. Safranski, CC-1047 (1943). 686. R. Fryxell, CC-1448 (1944). 349 687. 688, 689. 690 - 691. 692. 693. 694, 695. 696, 697 . 698. L. Warf, CC-1194 (1943). H. M. Feder, R. P. larsen, M. Beederman, H. E. Evans, ANL- 5103 (1953). BNL-583 (1959); NSA 14, 17642 (1960). W. Sborgl, Z. Elektrochem. 19, 115 (1913). Jo A. McLaren, D. W. Clline, H. 8. Clinton J. Ho Goode, J. A. Westbrook, K-587-(19505. ?iggg%odney, U. 8. Patent 2,872,387 (1959); NSA 13, 13320 British Patent 829,090 (1960); NSA 14, 944 (1960). C. D. Calkine, R. B. Filbert, Jr., A. E. Bearse, J. W. Clegg, BMI-2434 (1950). J« d« Flnley, E. W. ChristoRherson, H. R. Grady, R. W. Woodard, C. E. Larson, AECD-4181 (1946); NSA 10, 107h0 (1956). L. Steadman, "The Pharmacology and Toxicology of Uranium Compounds,” C. Voegtlin, H. C. Hodge, edltors, NNES, Division VI, Volume 1, Chapter 19, Sectilon 4, McOGraw-Hlll Book Co., New York, 1953. F. S. Grimaldl, I. May, M. H. Fletcher, J. Titcomb, Geol. Survey Bull. 1006 (1954). "Handbook of Chemical Methods for the Determination of Uranium in Minerals and Ores,”™ His MajJesty's Stationery Office, London, 1950. 350 NUCLEAR SCIENCE SERIES: MONOGRAPHS ON RADIOCHEMISTRY AND RADIOCHEMICAL TECHNIQUES See the back of the title page for availability information ELEMENTS Aluminum and Gallium, NAS-NS-3032 [1961] Americium and Curium, NAS-NS-3006 [1960] Antimony, NAS-NS-3033 [1961] Arssnic, NAS-NS-3002 (Rev.) [1965] Astatine, NAS-NS-3012 [1960] Barium, Calcium, and Strontium, NAS-NS-3010 [1960] Baryllium, NAS-NS-3013 [1960] Cadmium, NAS-NS-3001 [1960] Carbon, Nitrogen, and Oxygen, NAS-NS-3019 [1960] Cesium, NAS-NS-3035 [1961] Chromium, NAS-NS-3007 (Rev.) [1963] Cobalt, NAS-NS-3041 [1961] Copper, NAS-NS-3027 [1961] Fluorine, Chlorine, Bromine, and lodine, NAS-NS-3005 [1960] Francium, NAS-NS-3003 [1960] Germanium, NAS-NS5-3043,[1961] Gold, NAS-NS-3036 [1961] Indium, NAS-NS-3014 [1960] Iridium, NAS-NS-3045 [1961] Iron, NAS-NS-3017 [1960] Lead, NAS-NS-3040 [1961] Magnesium, NAS-NS-3024 [1961] Manganese, NAS-NS-3018 (Raev.)[1971] Mercury, NAS-NS-3026 (Rev.) [1970] Molybdenum, NAS-NS-3009 [1860] Nickel, NAS-NS-3051 [1961] Niobium and Tantalum, NAS-NS-3039 [1961] Osmium, NAS-NS-3046 [1961] - Palladium, NAS-NS-3052 [1961] Phosphorus, NAS-NS-3056 [1962] Platinum, NAS-NS-3044 [1961] Plutonium, NAS-NS-3058 [1965] Polonium, NAS-NS-3037 [1961] Potassium, NAS-NS-3048 [1961] Protactinium, NAS-N5-3016 [1959] Radium, NAS-NS-3057 [1964] Rare Earths— Scandium, Y ttrium, and Actinium, NAS-NS-3020 [1961] Rare Gases, NAS-NS-3025 {1960] Rhenium, NAS-NS-3028 [1961] Rhodium, NAS-NS-3008 (Rev.) [1965] Rubidium, NAS-NS-3053 {1962] Ruthenium, NAS-NS-3029 [1961] Selenium, NAS-NS-3030 (Rev.) [1965] Silicon, NAS-NS-3049 (Rev.) (1968] Silver, NAS-NS-3047 [1961] Sodium, NAS-NS-3055 [1962] Sulfur, NAS-NS-3054 [1961] Technetium, NAS-NS-3021 [1960] Tollurium, NAS-NS-3038 [1960] Thorium, NAS-NS-3004 [1960] Tin, NAS-NS-3023 [1960] Titanium, NAS-NS-3034 (Rav.) [1971] Transcurium Elements, NAS-NS-3031 [1960] Tungstan, NAS-NS-3042 [1961] Uranium, NAS-NS-3050 [1961] Vanadium, NAS-NS-3022 [1860] Zinc, NAS-NS-3015 [1960] Zirconium and Hafnium, NAS-NS-3011 [1860] TECHNIQUES Absolute Measurement of Alpha Emission and Spontaneous Fission, NAS-NS-3112 [1968] Activation Analysis with Charged Particles, NAS-NS-3110 [1966] Applications of Computers to Nuclear and Radiochemistry, NAS-NS-3107 [1962] Application of Distillation Techniquas to Radiochemical Separations, NAS-NS-3108 (1962] Cation-Exchange Techniques in Radio- chemistry, NAS-NS-3113 [1971] Chemical Yield Determinations in Radio- chemistry, NAS-NS-3111 [1967] Detection and Measurement of Nuclear Radiation, NAS-NS-3105 [1861] Liquid-Liquid Extraction with High- Molecular-Weight Amines, NAS-NS-3101 [1960] _ Low-Level Radiochemical Separations, NAS-NS-3103 [1961] Paper Chromatographic and Electromigration Techniques in Radiochemistry, NAS-NS- 3106 [1962] Processing of Counting Data, NAS-NS-3108 [1965] Rapid Radiochemical Separations, NAS-NS- 3104 [1961] Separations by Solvent Extraction with Tri-n-octylphosphine Oxide, NAS-NS-3102 [1961] Current as of January 1972 Radiochemistry of Uranium . NAS-NS-3050 - USAEC