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OAK RIDGE NATIONAL LABORATORY
operated by

UNION CARBIDE CORPORATION w
NUCLEAR DIVISION

for the
U.S. ATOMIC ENERGY COMMISSION

ORNL- TM-2180

DATE -March 26, 1968

ELECTRICAL CONDUCTIVITY OF MOLTEN FLUORIDES.

A REVIEW.

G. D. Robbins

NOTICE This document contains information of a preliminary nature
ond was prepared primarily for internal use ot the Oak Ridge National
Laboratory. It is subject to revision or correction and therefore does
not represent a final report.

ISTRECTON OF THIS GOUMET & UNKIMITER
 

 

LEGAL NOTICE —

 

This report was prepared as an account of Government sponsored work. Neither the United States,

nor the Commission, nor any person acting on behalf of the Commission:

A. Mokas any warranty or representotion, expressed or implied, with respect to the accuracy,
completeness, or usefulness of the information contecined in this report, or that the use of
any information, apporatus, method, or process disclosed in this report may not infringe
privately owned rights; or

B. Assumes any liabilities with respect to the use of, or for damages resulting from the use of
any information, apparaotus, method, or process disclosed in this report.

As used in the cbove, ‘‘person acting on bshalf of the Commission’' includes any employee or

centractor of the Commission, or employee of such contractor, to the extent that such employes

ot contrector of the Commission, or employee of such contractor prepares, disseminates, or
provides access to, any information pursuant to his employment or contract with the Commission,
or his empioyment with such contractor.

 

 
iii

ELECTRICAL CONDUCTIVITY OF MOLTEN FLUORIDES.
A REVIEW

G. D. Robbins

Reactor Chemistry Division
Oak Ridge National Laboratory
Oak Ridge, Tennessee

ABSTRACT/SUMMARY

A review of electrical conductivity measurements
in molten fluoride systems covering the period 1927 t?
1967 has been made, with particular emphasis on experi-
mental approach. It is pointed out that the common
practice of measuring resistance with a Wheatétone
bridge having a parallel resistance and capa01tanc?,
R_ and C_, in the balancing arm can result in cons;def-
agle error if the relation Rp = Rs[l + szcpz(znf) ] is
not employed in determing the solution resistance, Rs'
The frequency dependence of the measured resistance and
the practice of extrapolating measured resiétances to
infinite frequency versus 1/Nf is examined in térms of
electrode process concepts. A summary of experimental
approaches and results for 56 molten fluoride systems

is presented.

LEGAL NOTICE

 

Thia report was prepared as an account of Government sponsured work, Neither the United

States, nor the Commiagion, nor any person acting on behalf of the Commigsion:

racy, 1 ful

Privately owned rights; or

B. Assumes any liabilities with veapect to the use of, or for damages regulting from the

uge of any information, apparatus, method, or procesa disclosed in this report,

Ag uded in the above, ‘'person acting on behalf of the Commiaaton” includes any em-
ployee or contractor of the Commission, or emplovee of such contractor, to the extent thet

such employee or contractor of the Commisaion, or emplayee of suck contractor

disseminates, or provides access te, any information pursusnt to hig employment or contract

with the Commisalon, ar his employment with such contractoer.

 

A. Makes any warranty or Tepresentation, expresaed or implied, with respect to the acou-
or £ ot

of the ed ir this report, or that the yse
of any faformation, appargtus, method, or prucess disciosed {n this report may not infringe

  
  
   
 
   
 

Prepares,

 
ELECTRICAL CONDUCTIVITY OF MOLTEN FLUORIDES.
%*
A REVIEW

Introduction

Invesitgation of the electrical conductivity of molten
salt systems has been an area of lively research in recent
years, and a number of reviews have appeared which deal with

this aspect of transport phenomena.(1_3)

It will be the
intent of this review to limit itself to the subject of
conductance measurements in molten fluorides. The containment
problems encountered with these materials set them apart from
the other molten halides with respect to experimental diffi-
culties and the consequent precision of measurement which can
be expected. By limiting this review to fused fluorides, it
is hoped that sufficient details may be presented to permit
workers in the field to obtain a comprehensive survey covering
the period 1927 to 1967. To our knowledge, no such review
exists which addresses itself to the questions which we pose
below.

Many investigations in the past have been concerned with
cryolite-containing melts because of their relevance to the
aluminum inaustry, and a review of these systems has been given

(4)

by Grjotheim and Matiasovsky. Renewed interest in the trans-

port properties of fused fluorides in general has resulted from
their use as fuel, blanket, and coolant materials in molten

(5)

salt reactors.

 

*
Research sponsored by the U.S. Atomic Energy Commission
under contract with the Union Carbide Corporation.
Because of the high specific conductance of most molten
salts (1-6 Q71 cm_l),(é) experimental approaches have tended

(1),

to fall into two groups (1) use of capillary-containing

cells, which results in a cell constant of several hundred
cm !, the capillaries being constructed from electrically
insulating materials; or (2) use of metallic cells in which
the container is usually one electrode, with a second electrode
positioned in the melt. The latter type of cells have cell
constants of the order of a few tenths cm !, requiring very
accurate measuring bridges and determination of lead resist-
ances. Since the value of measured resistance in such cells
is less than 1@, errors due to temperature gradients, changes
in cell constant with temperature, and polarization become a
significant problem. Hence, cells of type (1) are clearly
desirable for use in molten salts. However, electrically
insulating materials for capillary construction which are
resistant to attack by molten fluorides are scarce.
Measurement of electrical conductivity in molten salts
differs from similar studies in aqueous solutions in several
significant aspects. It is often the practice to employ some
form of a Wheatstone bridge(7) (Figure 1) in which the two
upper arms are matchéd, standard resistances, and the imped-
ance of the cell in one lower arm is balanced by a variable
impedance, Z, in the fourth arm. The balancing impedance is
usually a variable resistance, Rp, and capacitance, Cp,

connected in parallel. The solution resistance, R and

S’
solution-electrode interfacial capacitances, Cs’ in the cell

(8)

are considered to be in series (Figure 2). By requiring
one electrode to have a much greater area than the other, the
impedance associated with such an electrode becomes negligible,
and the equivalent circuit reduces to that shown in Figure 3.
(Alternatively, one can employ electrodes of similar area and
treat the capacitance resulting from their series combination

as a single total capacitance, é— = %— + 6L .)
S @2

s
tance resulting from the electrode leads is in parallel across

The capaci-

the entire cell shown in Figure 2. However, at frequencies
ordinarily employed, and with some care in positioning, this
capacitance can be neglected.

When a sinusoidal alternating potential is impressed across
the cell, a sinusoidal alternating current results. If the
potential is insufficient to cause electrochemical reactions
to occur at the electrodes, the equivalent circuit of Figure 3
is valid, and the interfacial capacitance is charged and dis-
charged during each half-cycle through the solution resistance.
By employing an oscilloscope as the null detector, one can
balance the cell impedance with the parallel combination of Rp
and Cp showe in Figure 1. The two balance equations (when the

standard resistances are matched) are

R C
S P _
+ == =1 (1)
R_ Cg
and
2 =
RSRpCSCp(ZHf) 1 (2)
These may be combined into
= 1 2 2 2
R, R[1 + s (21f)2] (3)

It is often the practice to equate Rp ( the value of the bridge
dials) to RS (the true solution resistance).(g’lo) (In the case

of unmatched standard resistors, their ratio is used.) This
is usually valid in aqueous solutions where RS and CS are such
as to result in szcpz(ZHf)2 being negligibly smaller than
unity. However, in molten salts experimental conditions for
the measurement of electrical conductance can result in
considerable error if tﬁese equations are not considered when
using parallel components in the balancing arm of a Wheatstone
bridge. For example, on rewriting equations (2) and (3) in
the form

1

R_ = Rs[l + E;fﬁ;??iﬁ;jf ] (4)

p

it is evident that in molten salts, where RS2 may be smaller by
*

a factor of 10! % that in aqueous solutions (CS having approxi-

(13))

mately similar values an awareness of these relations is
necessary.

Use of equation (3) to calculate R, is limited by the
accuracy with which the values of the variable capacitance,
Cp, and the frequency are known. Use of precision capacitors
can be avoided by employing a bridge in which the balancing
components are in series.(l4) Then in the case of no electro-
chemical reaction, the value of RS is well represented by the
reading on the balanced bridge; however, this method does
require the use of large capacitors.

When a sufficiently large a.c. potential is impressed on
the cell that charge is transferred across the solution-
electrolyte interfaces during part of each half-cycle, corres-

ponding to an electrochemical reaction, the situation becomes

considerably more complex. However, it is under these conditions

 

—%
The measured resistance of 0.0005 m KC1 in cells employed

by Jones and Bollinger(ll) was approximately 50,000 £. Cuthbertson

(12)

0.5  in molten cryolite.

and Waddington report a measured resistance of approOximately
that conductivity measurements are usually performed. Based

(15)

on the work of Jones and Christian, resistance in aqueous
systems is generally measured at a series of frequencies and
extrapolated to infinite frequency employing the functional
form f_%. Use of this particular functional form is attri-

buted(15) (16,17) (18)

to Warburg and Neumann who, on the basis
of Fick's laws of diffusion, predicted that the polarization
resistance (that part of the measured resistance due to elec-
trode polarization) was inversly proportional to NT.

Applying the concepts resulting from electrode process
studiesflg-?l) one may envision the equivalent circuit shown
in Figure 4 for an electrode-solution interface across which
charge is being transferred. {%?represents the impedance
associated with the reaction, which is in parallel with the
solution-electrode interfacial capacitance. Under the exact-
ing assumptions of faradaic impedance studies, zrnmy be re-~
presented by a frequency-independent resistance, 6, in series
with a frequency-dependent impedance, -W-, the Warburg imped-
ance. The latter is conveniently represented gg a resistance
and capacitance in series, Rr and Cr’ at constant frequency
(Figure 5). At a given frequency the impedances resulting from
R, and C, are equal., However, both vary as f_%.

The assumptions upon which the mathematical analysis
which results in f”% dependance oer and Eﬁ%ﬁ; rests include
1) semi-infinite linear diffusion of reactants and products
and 2) a small amplitude a.c. potential superimposed on a net

d.c. polarizing potential. These are not the conditions of

conductivity measurements. However, during that part of each
half-cycle during which reaction is occurring at the electrodes,
the equivalent circuit of Figure 4 is a useful concept, even
though Zr may not be treated rigorously according to Figure 5.
‘That the above considerations lead to the same frequency
dependence as that experimentally determined for many conduc-
tivity measurements(l59 renders this conceptual analysis
worth considering.

In brief, then, one may consider the equivalent circuit
of Figure 4 as a rough analog of the solution resistance,
electrode-solution interfacial capacitance, and reaction
impedance (bearing in mind that . cannot be represented
exactly by any finite combination of resistance, capacitance,
and inductance which will render it frequency independent).
During that part of each half-cycle in which the potential is
below that which results in an electrode reaction, the equi-
valent circuit of Figure 4 reduces to that of Figure 3, i.e.,
Zr becomes infinite. It is also useful to consider the equi-
valent circuit of Figure 4 in view of the practice of extra-
polating measured resistance to infinite frequency. It can
be seen that at infinite frequency the impedance of Cs is
infinitely less than that of Zr’ and Figure 4 again reduces
to Figure 3.

It should be emphasized that while one measures resist-
ance at a series of frequencies and extrapolates to infinite

frequency, one does not make measurements at frequencies

which approach infinity. In fact, very high fréquency measure-

ments (in the megahertz range) are to be avoided because of the
increased admittance of the leads and the fact that at very high

frequencies one ceases to measure a property assoicated with ionic
mobility and observes properties associated with dipole moments
and polarizabilities. Hence the question of concern remains
viz, what functional form of the frequency does one employ to

extrapolate the measured resistance to infinite frequency?

(22)

Robinson and Stokes consider this question in terms

of electrode process concepts as applied to aqueous media and
give balance equations for a bridge with a parallel-component

balancing arm, assuming various relative magnitudes of Rs’ o,

(15)

and Rr' Under the conditions employed by Jones and Christian,
1
f 2 dependence is predicted. Robinson and Stokes conclude that

one should measure resistance as a function of frequency and

extrapolate to infinite frequency in accordance with the observed

behavior. This is also the conclusion of Nichol and Fuoss,(23)

who observed a f ! frequency dependence of resistance in methanol

solutions.
In molten salts frequency dependence of the resistance has

been reported at polarizing potentials much lower than required

(24,25) (26)

for faradaic processes. Buckel and Tsaussoglou have

found that measured resistance vs. frequency plots show a plateau
in the range 10-100 kHz in adqueous potassium chloride and molten
potassium bromide. They suggest that extrapolation of resistance

1
vs. £ 2 would lead to erroneous conductances and that one should

study frequency dispersion in a particular apparatus and select

a frequency-independent region for performing conductivity
(27) reported that in molten nitrate

1
melts plots of measured resistance vs. f 2 were not linear, but

experiments. De Nooijer

approached linearity as the frequency approached infinity. His
values of measured resistance at 20 kHz only differed from values
extrapolated to infinite frequency by about 0.1 %. Winterhager

(28,29)

and Werner have considered frequency dispersion in molten

nitrate, chloride, and fluoride melts and have applied '"electrical

locus curve theory"(3o)

to their results obtained employing a
Thomson-type bridge. They conclude that at sufficiently high
frequencies measured resistance becomes independent of frequency,
and they employ a measuring frequency of 50 kHz., Therefore, in
this review particular attention will be given to the observed
behavior of resistance with frequency and to the condition of
the electrode surfaces, since in aqueous mdeia it is observed
that frequency dispersion is less in cases of heavy platiniza-
tion (increased CS).(ll)

In light of the foregoing discussion the following informa-
tion was sought from each study which was consulted:

A. Cell material, its general design, and the resulting cell

constant, (£/a), or general range of measured resistance,

iR} .

B. Electrode material, shape, size, and surface character.
C. Type of bridge employed.*

D. Frequency range employed.

E. Dependence of measured resistance on frequency.

F. Voltage applied to the bridge.

G. Results. Results are reported either in terms of the

 

The general types of bridge circuits employed are shown
in Appendix I as an aid in description. The circuits actually
employed were usually modified versions of those shown. For
details of circuity, the reader is referred to the cited work,
specific conductance, «, the equivalent conductance, qu,

or the molar conductance,‘Am. These quantities are defined

 

 

as
_ 1
kK = ﬁ-(ﬂ/a) (5)
eq _ equivalent weight
A - density (6)
m _ molecular weight
A « - density (1)

These quantities are reported as functions of temperature for

the minimum, maximum, and one intermediate value for pure salts.

For binary mixtures a 3 x 3 grid also stating the extremes and

one intermediate value of composition is employed where conven-

ient. Conductivities of mixtures of more than two components

are presented in a manner designed to convey maximum information.
The tabulation is ordered according to the system under

consideration; and within each system, by date of publication,

the earliest appearing first. Where one investigation has

covered several systems, a cross reference is given. Additional

values of k and A may be found in Janz's Molten Salts Handbook(31)

 

for many of the systems reported here. As previously stated,
the primary concern of this review is topics A-F. The results
presented herein are given for comparison and completeness and
were, in all cases, taken from the original publications
(exception: Appendix II).

It will be observed below that a number of publications
have not addressed themselves to some of the questions raised
above, If this review serves only to remedy this practice, it

is considered justified.
TABULATION

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

f .
Cell Pridge Range vop Results _
J System  Ref i or (4fa) Electrodes ] {(Detector) (kHz) R va. f {v) T(°C) w2 lem ) or Alem?legq™ (mol™'))
‘“;‘ LiF 32 Pt crucible iR} = 0,182 Pt crucible and platinized Pt ¥Wheatstone 6 N.8. = Not N.S8. K
foil (3 x 4 mm) (telephone} Stated 905 20.2
950 23.4
. .- 995 27.2 (+5 to 10%)
2 LiF 33 Two Pt (80%) - Rh hemispheres (d = " &|Two Pt (B80%) - Rh rods (d - .01")| Specially develd N.S. N.S8 N.8 847 _ ) et
2"), These are also current electrodes |These are potential-measuring oped by E. Fair- 102; kK = 3.805 + 1,004x10 2T(°C) - 3.516x10 *T
electrodes. stein. (34)
f range=.2-6 kHZ
R range=.01-108
(oscilloscope) - -
$ 4 - (g-.0082 1cm 1)
3 LiF 35 Hot-pressured BN ecylinder (id - 3/16") |Inconel red and inconel plate ¥heatstone, na 2 "did not vary (N.8.{ gqno K = 8.43
36 surrounded by grthite {RS ~ 3-6 1. acrogs ends of BN cylinder. capacitors appreciably O=1.05 A% - 158
s/a) — 17-39 cm (oscilloscope) between 1 and
20 kHz (£ 1%)
4 LiF 24 | Pt crucible (vol. 319 em) {(f/a) = Two platinized Pt foils (10 x 10 | Thomson-type 50 f-dependency |~.05]| g75 8.663
29 0,28 cm ! mm) (oscilloscope) at lower f, 958 9.058
independent at 1037 9.306
50 kHz
& LiF 37 Graphite crucible (1d 3.5, 5" deep) [Two " Mo tubes fitting into Jones (null 10 f independent { N.S 870~ kK = 9.06 + 5.83x1072(T~-870°C)
containing 2 BN cylinders (id ~ 3/16") |upper portions of BN cylinders detector) 1-20 kHz 1010 A%9 . 1p0.8
encased in graphite and enlarged at tog o=1.2 .
to accomodate e¢lectrodes, (£/a) & 100cm (41%)
& NaF 38 | Pt crucible (400 ml), (£/a) = 0.0835cm?|Hemispherical Pt electrodes, Kelvin N t‘ﬁ Ro £2 1o K A9
39 platinized originally. 4 extrapolated 1000 5.52 118
to f = @ 1040 5.74
o 1080 5.95% (tseveral %)
I e .
7 NaF 40 | Pt crucible (0.2 mm wall) ER} o 0.02 2(Crucible and a Pt cylinder (area | N.S. .15 | N.8. N.S.| 997 K o= 5.2
. o -~ 2 cm?), both platinized to 8
¢ : ’ #3 43 #3 #3
8 NaF :Z #3 #3 # # " # 1020 k = 6.15
- A®9 .
o O=1.05 A 113 (£ 19)
9 NaF 28 | #4 #4 #4 #4 | #4 #4 1003 4.960
29 1086 5.179
1138 5.335%
- s 5 #5 5 | #s #5 - -
S e & ‘ # iggg K = 5.29 + 5,.64x10 ¥ (T-1030°C)
eq
e=1. - .
1.2 A 156.6 (£1%)
11 | x¥ 3z| A1 #1 #1 # 4 #1 K
860 4.14
900 4.28
1 .7
000 4.7 (x5 to 10%)
12 | KF 13| 42 #2 #2 #2 | #2 #2 | se9 K = —3.493 + 1.480x1072T(°C)
1040 -6.608x10 °T? - -
(o=.009% lcm™ 1)

 

 

 

 

 

 

 

 

 

 

0T
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

£ Result
Cell Bridge Range Vpp esults L _
System Ref fR} or (2/a) Electrodes (Detector) (kHz) Rvs. f (v) T(°C) (2 lem ™) or Alem?Q leq™! (mol™!))
13 | XF 35 | #3 #3 #3 #3 #3 #3 900 xe= 3.80
36 e=1.05 A% = 124 (£1%)
14 | KF 28 | #4a #4 #4 #4 #4 #4 859 3.573
29 938 3.793
1012 4.021
15 KF 3% MgO, single crystal, dip cell; Pt Container and Pt electrode Jones .5-10] varied <0.3% | N.S 905 3.77 (2%
43 copntainer over £ range 2
-2 o
16 | CsF 33 1 #2 42 #2 #2 2 #2 725~ « = -4.511 + 1,642x10 2T(°C)
® ' # # 921 -7.632x10 ¢T? (o=.0092  cm™)
17 CsF 42 | #15 #15 #15 #15 #15 #15 737 2.51
43 784 2.73
852 3.03
18 | AgF 28 | # 4 4 4 4 4 590 4.0%
g 28 $4 # # # # # 670 6.0%
19 BeF, 44 Pt-Rh (20%) crucible_(id = 2", ht, Crucible and Pt-Rh (20%) bob "Wheatstone 2-10 f independent | N.S. ® -5
45 | (2/a) = .11 or .28cm ! R-C bridge" 2-10 kHz 700 ¢.71 x 10_5
(scope or VTVM) 800 15.3 x 1(_)5
950 236 x 10 (£10%)
2y | CcaF, 46 | carbon crucible Mo electrodes N.S. N.S. [N.S. N.s. | 1418 « = 3.56
21 { MnF 28 | #4 4 #4 #4 4 4 940 4.7,%
: 29 # # # # 990 5.0% -
22 | CuF 28 | #4 4 4 q 4 4 970 2.2¥
uF, 28 # # # # # # 1110 2.5%
23 | ZnF 28 | #4 1 4 4 4 #4 900 3.24%
e 29 | # # # # 960 3.7%
z4 | poF, 28 | #4 #4 #4 #4 #4 #4 820 5.1%
29 1000 5.8%
25 KBF, 28 #a #4 #4 #4 #4 #4 545 1.052
¢9 569 1.126
652 1.245
26 | Na,TaF, |28 | /4 4 #4 #4 #4 4 702 1.165
$TaF; |28 # # 733 1.396
814 1.595
27 | K,TiF, |28 | #4 #4 #4 44 Ad #4 343 1.346
29 888 1.435
976 1.604
28 | K,TaF 28 | 44 #4 #4 #4 #4 #4 747 0.7285
2 7 39 800 0.9193
887 1.0366

 

 

1T
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

cell Br idge Range vop Results
(g * - - - - -
System  Red R} or (i/a) Electrodes {Detector) kHz) R vs. f (v)  T(°C) k(2 tem 1) or Alem*Q'eq ! (mol7!))
A T T— L L mmmnd - = -
20 | LigAtF, |38 | 91 Wi #3 #3 | #3 #3 1800 ko= 3.45%
' i) 920 K = 3.87%
T WA AIF, T17 | Fuscd Mg tube (d .99, £ - 10.3 cm) “1draphite plates across ends of Wheats tone, K two | N.S, N.S.
(2/2) - 0752 em ! tube and £ in 'y 1020 x = 1.5
parallel cor
{telephone)}
- - —" - . L3
51| NaGAVE. | 391 F6 #6 #6 #e | #e #6 11000 2.80 980
1040 2.90  A®Y = 2,744 - wrvpy
L 1080 3.00 (» severalD
32 | Na,ALF, |40 | 47 #7 #7 #7 #7 #7  [lol3 K o= 2.8;*
o o | #3 #3 #3 #3 #3 3 at
3t | Na,AlF, 3 ‘ ” ! 1000 2.8O* 284 at 1010°
36 1060 2.95% 296 at 1040°
34 | Na;ALF, 28 | 4 #4 #4 #4 #4 #4 1025 2.8¢%
29 1120 3.0,*
i+ | Na,a1F, [ 47 | Pt nemisphere (od - 4 em), (t/a) - Container and Pt rod (d = 3 mm) Thomson plus 5 N.8 ¥.5- 11000 2. 84
386 em phase indicator 1040 z.92
1080 3,00
o | KoALE, N PN #3 #3 #1 | #3 #3000 5 32e
36 1060 2.42%
S ;‘A . ) LiF-ThF
i !nig * T " #3 #5 #5 #5 #s §E.§-3.5(m%) kK = 7,14 + 10.97x10 ¥ (T-880°C)
* A - 117.2, for @ = 1.2
78-22 (m%) x = 2,50 + 7.58x107 % (T-640°C)
A®9 - 29,9, for 0 = 1.2
50,2-49.8(m%) x = 2.13 + 4.19x107*(T-820°C)
aA%q . 31,0, for & = 1.2 (1%
14 LiF+UF, 37 F #s #5 #5 #5 #5 #5 LiF.UF -
I35 (wh) K = 7.55 + 5.86x1073(T-900°C)
eq
A =99,3, for © = 1.2
60-40(m%) « = 2.17 + 5.68x1073(T-700°C)
A®9 - 23,8, for @ - 1.2
40~60 (m%) kK = 2.89 + 3,29x107% (T-900°C)
A% = 33,5, for @ = 1.2 (.,
39 | NaF 48} Pt crucible {R}> 0.1 Curcible and Pt rod, both Carey-Foster 1 N.S. N.8. 500 837
CaF, platinized originally 1000 ‘;'373
(67 wi) °
1100 5.879 (z.5%)

 

gt
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

£ Vpp Results
Cell . Bridge Range - - - - -
o System  Ref Rt or (i/a) Electrodes (Detector) (kHz) R vs, f v) T(°C) k(@ tem™) or A(em*2 leq”! (mol™}))
®
40 | NaF + 481 439 739 #39 #39 #39 #39 1900 4,441
SrF, 1000 4,961
(67 wh) 1100 5.642 (,5%)
K
41 | NaF + 48 | #39 #39 #39 #39 #39 #39 900 4.027
BaF, 1000 4.602
(67 wi) 1100 5.319 (£.5%)
®
42 NaF + 49 | Hot-pressed BeQ tube in a_cylindrical Pt crucible across bottom of Wheatstone, _R" 1 N.S8. N.S.N F-ZrF 565° 7300.‘ aBs®
ZrF, Pt crucible {(#/a) & 24 cm'! the tube and Pt rod at top and 2 in a ; r- ) ]
parallel - ! ’ - :
(oscilloscaope) 50-50(m%) 0.52 0.92 1,73 (£10%)
43 | NaF + 37| #5 #5 #5 #5 #5 #5 [NaF-ThF _
T 'EB-IZTn% k = 3,49 + 3.74x107*(T-900°C)
A%9 - 71,3, for ©@ = 1.2
67-33(m%) k = 1.76 + 3.88x107* (T-800°C)
A®% - 28.1, for © = 1.2
50-50(m%) ® = 1,48 + 5,23x10 2 (T-800°C)
A9 - 28.6, for 8 = 1.2 (£1%)
; ; NaF-UF ' _
# 3:‘? ’ ks #s #s #s #5 #3 BE-TETm) x = 2.81 + 3.56x10 2 (T-850°C)
A®% - 57,7, for @ = 1,2
65-35(m%) k = 1.37 + 4.65x1072 (T-700°C)
A®% - 25,6, for & = 1.2
25+ 75 (m%) k = 2,18 + 3.56x10 ? (T-900°C)
Aeq = 36,9, for 8@ = 1.2 (£1%)
K
45 | NaF + 50 | Described in Ref. 51, not readily Pt electrodes Wheatstone, 5 N.8. N.S.| NaF-NaBF 450° 650° 800°
NaBF, available with balancing -4 A - - T.502
o 40-60(wth) 0.965 6.350  14.10s
(oscilloscope) 10-90{(w%) 2.408 8.801 14.978
K Aeq
46 | NaF + 3B | #6 #6 #6 #6 #6 #6 | NaF-NajAlF 1000° 1040° 108¢° 1006°
Na,AlF, |19 7692 T 3. To0 T4
50-50(m%) 3.19 3.30 3.41 99
35.7-64.3 (m%) 3.12 3.23 3.33 100
o
47 | KF + 50 | #45 #45 #45 #45 #45 #45 | KF-KBF 450° 650° goa°
KBF, TO-30Te%) = —— T5.o01
40-60 (W) - 2.255 11.495
10+90 (w¥h) 0.281 3.601 12.703
Wheatstone, BT (data taken Irom graphs)
48 | MgF; + 52| Pt cell N.S. and & in N.8.| N.S8 N.S| MgF, -Na,ALF. %1070
Na,AlF, parallel = W =3
(oscilloscope) 10-90 (wdl) 2.2
1-99 (w%) 2.8

 

 

 

 

 

 

 

 

 

¢T
f

 

 

 

 

 

 

 

 

 

Cell Bridge Range Vp Results
ste .. P - I -
System  Ref R or (£/a) Electrodes {Detector) (kHz) R va, § (v)  TCC) (@ cm!) or Alcu?fieq™! (mol”!))
i °
49 CaF, + 53 | Graphite crucible {R}w 0.58 Carbon ancde and molten Al Wheatstone, & two N.S. N.B. g—g—%ﬁ;ﬁﬂi -—;go—o
Na;AlFg 12 cathode and in f'n 40-60(m%) 140
parallel 13-87 (%) 185
{telephone)}
K
. ; eq
RO | CaF; + | 38| #6 #é #é #6 | #6 #6 | caF,-Na ALF 1000°  1o040°  1080°  “lcoo°
Na;AlF, 39 - T .Y T. 8T
23-77(m%) 2.68 2.79 2.90 83
12.3-87.7(m%) 2.74 2.85 2.95 88
- o T A"
51 | car, = | 35| #3 #3 #3 #3 #3 #3 1010 232
Na,AlF, | 36
(A1m™) 1040 242
® o
52 AlF, - 52 | #48 #48 #48 #48 #a8 #48 A].E' -Na DA]F z_}g_?ﬂ
Na,AlF, 7.5-92.5(w%) 2.6
2.5-97.5(wh) 2.8
- = o
3| AIF, v 38 A6 #é #6 #6 #6 #6 ALF, -Na AIF 1000° 1040° 10800 D1goa®
a, b 39 - w0} 60 BT
11.6-88.4(m%} 2.68 2.77 2.86 88
: — - -- 0 2.12¢%
a4 LiAlF + ] 35 ] #3 #3 #3 #3 #3 #3 ™
Na,AlF, | 36 880 2.82%
(40w}
35 | LiF+NaF+ { 49 { Hemispherical Pt crucible (2/a) o 0,162 | Current electrodes: c¢rucible and | No bridge: .5 N.S N.S. 222 i;g:
KF (46, 5- Pt spherc; potential electrodes: | VTVMN and 815 1‘80“
11.5-42 crucible and Pt cylinder amme ter -
m7) surrounding sphere (220%)
- =%
56 NaF+ZrF,H 49 | #55 #55 #55 #55 #55 #55 NaF-ZrF,-UF 565° 730° 885°
UF, . 5-40-6.5(m%) 0.58 0.88 T.43
50-46-4 (m%) 0.79 1.08 1.60 (£10%)

 

 

 

 

 

 

 

 

 

 

7T

‘lnterpolated from a linear plot of «x ve. T

-+,

o = T wmeasured (°K)

melting
10.

11.

12.

15

REFERENCES

Janz, G. J. and R. D. Reeves, '"Molten-Salt Electrolytes -

Transport Properties," in Adv. in Electrochem.

 

and Elec. Eng., Vol. 5, C. W. Tobias, Ed., John Wiley and
Sons, New York, 1967.

Sundheim, B. R., "Transport Properties of Liquid Electro-
lytes" in Fused Salts, B. R. Sundheim, Ed., McGraw-Hill,
New York, 1964.

Klemm, A., "Transport Properties of Molten Salts,'" in

Molten Salt Chemistry, M. Blander, Ed., John Wiley and

 

Sons, New York, 1964,

Grjotheim, K. and K. Matiasovsky, Tidsskr. Kjemi Bergv.

 

Metallurgi, 26, 226 (1966).
Grimes, W. R., "Materials Problems in Molten Salt Reactors,"”

in Materials and Fuels for High Temperature Nuclear Energy

 

Applications by M. T. Simnad and L. R. Zumwalt, the M.I.T.
Press, Mass., 1964.

Yaffe, I. S. and E. R. Van Artsdalen, J. Phys. Chem., 60,
1125 (1956).

Jones, G. and R. C. Josephs, J. Am. Chem. Soc., 50, 1049

 

(1928).

Grahame, D. C., J. Am. Chem. Soc., 63, 1207 (1941).

 

Daniels, F., et al., Experimental Physical Chemistry, 5th

 

ed., McGraw-Hill, New York, 1956, p. 396.

Glasstone, S. and D. Lewis, Elements of Physical Chemistry,

 

Van Nostrand, Princeton, New Jersey, 1960, p. 430.

Jones, G. and G. M. Bollinger, J. Am. Chem. Soc., 53, 411

 

(1931).

Cuthbertson, J. W. and J. Waddington, Trans Faraday Soc.,

 

32, 745 (1936).
13,

14.

15.

16.

17.

18.

19.

20.

21,

22.

23.

24.

25.

26.

27.

Liu, C.H.

’

16

K. E. Johnson, and H., A. Laitinen, in Molten

Salt Chemistry, M. Blander, Ed., Interscience Publishers,

 

New York,

1964, p. 715.

Robbins, G. D. and J. Braunstein, Reactor Chemistry

Division
December
Jones, G.
(1935).

Warburg,
Warburg,
Neumann,

Grahame,

‘Grahame,

Delahay,

Annual Progress Report for Period Ending

31, 1967, ORNL-4229, p. 57.

E
E
E.
D
D
P

., Wied. Ann. Physik,

and S. M. Christian, J. Am. Chem. Soc., 57, 272

 

493 (1899).

 

 

, Wied. Ann. Physik, 500 (1899).

67,
., Drude Ann. Physik, 6, 125 (1901).
67,

 

C., J. Electrochem. Soc., 99, 370C (1952).

 

C., Ann. Rev. Phys. Chem., 6, (1955), pp. 345-6.

 

., New Instrumental Methods in Electrochemistry,

 

Interscience Publishers, New York, 1954, pp. 146-168.

Robinson,

R. A. and R. H. Stokes, Electrolyte Solutions,

 

Butterworths, London, 2nd ed.(revised), 1965, pp. 88-95.

Nichol, J. C. and R. M. Fuoss, J. Am. Chem. Soc., 77, 198

(1955).

 

Hills, G. J. and K. E. Johnson, J. Electrochem. Soc., 108,

 

1013 (1961).

Hiill, b. L., G. J. Hills, L. Young, and J. O'M. Bockris,

J. Electroanal. Chem., 1, 79 (1959).

 

Buckle, E. R. and P. E. Tsaoussoglou, J. Chem. Soc.,

De Nooijer,

London, 667 (1964).

B., "The Electrical Conductivity of Molten

Nitrates and Binary Nitrates," thesis, University of

Amsterdam,

The Netherlands, 1965.
28.

29.
30.

31.

32.

33.

34.

35.

36.

37.

38.

39.

40.

41.

17

Winterhager, H. and L. Werner, Forschungsber. des Witschafts-u.

Verkehrsministeriums Nordrhein-Westfalen, No. 438, 1957.

Ibid., No. 341, 1956.

 

Oberdorfer, G., Lehrbuch der Elektrotechnik, Bd.II, 1944,

 

p. 212.

Janz, G. J., Molten Salts Handbook, Academic Press, New

 

York, 1967.

Ryschkewitsch, E., Z. Elektrochem., 39, 531 (1933).

 

Yaffe, 1. S. and E. R. Van Artsdalen, Chemistry Division
Semiannual Progress Report for Period Ending June 20, 1956,
ORNL-2159, p. 77.

Fairstein, E., Instrumentation and Controls Semiannual
Progress Report for Period Ending July 31, 1955, ORNL-1997,
p. 9.

Yim, E. W. and M. Feinleib, J. Electrochem. Soc., 104, 622

 

(1957).

Ibid., 626 (1957).

Brown, E. A. and B. Porter, "U.S. Department of Interior,
Bureau of Mines," 128.23:6500 (1964).

Edwards, J. D., C. S. Taylor, L. A. Cosgrove, and A. S.

Russell, J. Electrochem. Soc., 100, 508 (1953).

 

Edwards, J. D., C. S. Taylor, A. S. Russell, and L. F.

Maranville, ibid., 99, 527 (1952).

Landon, G. J. and A. R. Ubbelohde, Proc. Royal Soc.,

 

A240, 160 (1957).

 

Bronstein, H. R. and M. A. Bredig, Chemistry Divisiocn
Annual Progress Report for Period Ending June 20, 1959,

ORNL-2782, p. 59.
42.

43.

44.

45.

46.

47.

48.

49-
50.

51.

52.

53,

54.

55.

18

Ibid., J. Am. Chem. Soc., 80, 2077 (1958).

 

 

Bronstein, H. R., A. S. Dworkin, and M. A. Bredig, Chemistry
Division Annual Progress Report for Period Ending June 20,
1960, ORNL-2983, p. 65.

Mackenzie, J. D., J. Chem. Phys.,32, 1150 (1960).

Ibid., Rev. Sci. Instr., 27, 297 (1956).

 

 

Badk, T., Acta Chem. Scand., 8, 1727 (1954).

 

Bajcsy, J., M. Malinovsky, and K. Matiasovsky, Electrochim.
Acta, 7, 543 (1962).

Thompson, M. deK. and A. L. Kaye, Trans. Electrochem, Soc.,

 

67, 169 (1935).
Greene, N. D., ORNL-CF-54-8-64 (1954).

Selivanov, V. G. and V. V. Stender, Russian J. Inorg. Chenm.,

 

4, 934 (1959).

Meerson, G. A. and M. P. Smirnov, Khimiva Redkikh Elementov,

 

Akad. Nauk SSSR, 2, 133 (1955).

 

Batslavik, E. and A. I. Belyayev, Russian J. Inorg. Chem.

 

3, No. 4, 324 (1958).

Pearson, T. G. and J. Waddington, Disc. Faraday Soc., 1,

 

307 (1947).

Malmstadt, H. V. and C. G. Enke, Electronics for Scientists,

 

W. A. Benjamin, New York, 1962, p. 273.

Dike, P. H., Rev. Sci. Instr., 2, 379 (1931).

 
19

(~ ) ORNL-DWG 68~-2215

 

 

 

 

 

 

 

 

 

 

 

"Figure 1: Wheatstone bridge: parallel-component balancing

arm.
ORNL-DWG 68—-2216

 

 

Figure 2: Equivalent circuit of cell in absence of reaction.

ORNL-DWG 68-2217

 

Re |
CS
Figure 3: Equivalent circuit of solution resistance and

electrode-solution interfacial capacitance in

absence of reaction.
20

ORNL-DWG 68—-221(8

 

 

 

 

 

 

_______AWVV_ "
" |

Figure 4: Equivalent circuit including reaction.

ORNL-DWG 68-2219
8 6 Rr Cr

 

Y

|
R R
s C, 5 Ce

CONSTANT FREQUENCY

Figure 5: Equivalent circuit for faradaic impedance studies.
21

ORNL-DWG 68- 2220

APPENDIX I
IMPEDANCE BRIDGES

. , N\

| —) \_/
(2,55)

JONES BRIDGE ' !
A WHEl;TSTONE Bi:lég?E. . 8. (WHEATSTONE BRIDGE,
NO CAPACITORS y! AND ¢ IN PARALLEL)
DETECTOR DETE@
CELL _ [ CELL |

N\ DETECTOR
T\ %

 

 

 

 

ARA AAA
Y vy

 

 

 

 

~AAA AAR
oy

 

     

 

 

C. KELVIN BRIDGE™® 2 [ceLL] D. THOMSON BRIDGE*”!
DETECTOR

Ll '
-

 

 

 

 

 

 

 

z
—
()
—/

Z2=IMPEDANCE OF CONNECTIONS

 

 

 

 

CAREY-FOSTER BRIDGE'*® |
F. (CELL AND S ARE INTER-
HOM
TvpE” BRDGE (2529 2 CHANGEABLE)

E. (EMPLOYED BY WINTER-
HAGER AND WERNER)

 

 

 

 

 

 

 

Z= IMPEDANCE OF CONNECTIONS

 
22

APPENDIX 11

For the sake of completeness, references to those
cryolite systems which could not be consulted in the original
are listed in this appendix. An indication of their content,
together with the secondary source, is given.
Batashev, K. and A. Zhurin, Metallurg, 10, 67 (1935); C.A.,

30, 7018”7 (1936).

(x of KF-AlF, system vs. T)

Batashev, K. P., Legkie Metally, 10, 48 (1936); ref. 4.

 

(x of cryolite vs. T)

Batashev, cited by Mashovets in The Electrometallurgy of

 

Aluminum (Russian), 1938; ref. 53.
(A™ of cryolite + NaF and cryolite + AlF;)

Vayna, A., Alluminio, 19, 215 (1950); C. A., 44, 10,549d
(1950) and ref. 4.

(k of cryolite vs. T; k of cryolite with additions of
NaF, CaF,, or AlF; near 1000°C)

Abramov, G. A., M. M. Vetyukov, I. P. Gupalo, A. A. Kostyukov,
and L. N. Lozhkin, "Teoreticheskie osnovy electrometal-
lurgii alyminia," Metallurizdat, Moscow (1953); ref. 4.
(x of cryolite vs. T)

Ponomarev, V. G., F. M. Kolomilskii, Yu. M. Putilin, Izvest.

Vysshikh. Ucheb., Zavedenii, Tsvetnaya Met., 1958, No. 6,

 

78; C.A., 53, 14,6701 (1959).

(« of K,TiFy vs. T)

Belyaev, A. I., Tsvetnye Metally, 31, No. 10, 61 (1958); C.A.,

 

53, 68321 (1959).
(x of cryolite with additions of LiF, NaF, BeF,, MgF,,

CaF,, BaF,, or AlF;)
23

Antipin, L. N., S. F. Vazhenin, and V. K. Shcherbakov, Nauch.

Doklady Vysshe! Shkoly, Met. 1958, 11; C.A., 55, 1241f

 

(1961).
(« of Na¥/AlF, ratios of 1.6 to 3.9)

Antipin, L. N, and S. F. Vazhenin, Tsvetnye Metally, 31, No.

 

12, 56 (1958); C.A., 53, 7824e (1959).
(k of cryolite with additions of CaF, or MgF,)

Chu, Y. A. and A. I. Belyaev, Izvest. Vysshikh. Ucheb.,

 

Zavedenif, Tsvetnaya Met., 2, No. 2, 69 (1959); C.A., 54,

 

24,0251 (1960).
(k of cryolite and cryolite with additions of LiF or BeF,)

Belyaev, A. I. and E. A. Zhemchuzhina, Tsvetnye Metally, 33,

 

No. 4, 45 (1960); C.A., 55, 1242a (1961).
(x of NaF/AlF; ratio of 2.2 to 2.78 with additions of MgF;)
Kuvakin, M. A, and P. 8. Kusakin, Trudy Inst. Met., Akad. Nauk.

SSSR, Unal. Filial, 5, 145 (1960); C.A., 55, 2255i (1961).

 

(x of cryolite)

Belyaev, A. 1., "Elektrolit alyuminievykh vann," Metallurgizdat,
Moscow, 1961; ref. 4.

(k of cryolite with BeF, additions up to 17 wt. % at 1000°C)

Matiasovsky, K., S. Ordzovensky, and M. Malinovsky, Chem. zvesti,
17, 839 (1963); ref. 4.

(« of cryolite vs. T)

Vakhobov, A. V. and A. I. Belyaev, '"Viiamie razlichnykh solevykh
komponentov (dobavok) na elektroprovodnost elktrolita
alyuminievykh vann," in "Fizicheskaya khima rasplavlemykh
solei,"” ed. by The Institute of General and Inorganic

Chemistry of the Soviet Academy of Science., Metallurgizdat,
2h

Moscow, 1965, pp. 99-104; ref. 4.
(v of cryolite with additions of LiF, MgF,, CaF,, BaF,,

or A1F; up to 20 wt. % at 1000°C)
O 00NN A W

mcqﬁ:b‘blﬁﬁqﬁ>t‘wcntjh’ﬁﬁqt‘EtﬁC)EtnC4C)m=ﬂE:h(3C)F1ﬁ'ﬁ*UdeCZODm(3(1COC)B>hiﬁﬁim

gtﬂ“ﬂhtﬁtqﬂt*G)Pﬁiw

HoObxAmnE

CtReEHOINPQOGAOAORH IO

INTERNAL DISTRIBUTION

Adams
Adamson
Affel
Alexander
Bacarella
Baes

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Bar ton
Bauman

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25

48.
49.
50.
51.
52.
53.
54.
55.
56.
57.
58.
59.
60.
61.
62 .
63.
64.
65.
66.
67.
68.
69.
70.
71.
72,
73.
74.
75.
76.
77,
78.
79.
80.
81.
82.
83.
84.
85.
86.
87.
88.
89.
90.
91.
92.
93.
94.

C.

QORISR DS ErSgOumnmOERYyEQnod SN OgawaEs QU r=E0 X

HEE =S =IO ZZ N E QYO

HEGRHEOEEEEEHQZ- gl mm=E

ORNL-TM-2180

Gabbard
Gammage
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Manning
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Martin
McCoy
McDuffie
McGlothlan
McHar gue
McNeese
Mesmer
95.

96.

7.

98.

99.

100.
101.
102.
103.
104.
105-119.
120.
121.
122.
123-124.
125.
126.
127.
128.
129.

153-154.
155,
156.

157-158.
159.

160-161.
162.
163.

164-178.

179-180.
181.

§C4C1m=UE:N=SHJcht4wtﬁFdﬁriC1W >

un

S. Meyer 130. G. P. Smith

L. Moore 131. R. W. Stelzner

M. Moulton 132. H. H. Stone

R. Mueller 133. R. A. Strehlow

P. Nichols 134, J. R. Tallackson

L. Nicholson 135. R. E. Thoma

C. Oakes 136. L. M. Toth

A. Posey 137. J. 8. Watson

L.. Redford 138. C. F. Weaver

D. Redman 139. A. M. Weinberg

D. Robbins 140. J. R. Weir

C. Robertson 141. M. E. Whatley

C. Robinson 142. J. C. White

A. Romberger 143. F. L. Whiting

W. Rosenthal 144. J. P. Young

G. Ross 145-146.. Central Research Library

C. Savage 147. Document Reference Section

lap Scott 148-150. Laboratory Records Dept.

H. Shaffer 151. Laboratory Records, ORNL

J. Skinner 152. ORNL Patent Office
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26

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