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Reactors-Special Features
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S ORNL-1956

“This document consists of 33 pages.

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Contract No. W-ThO5, eng 26

Reactor Experimental Engineering Division

ENTHALPIES AND HEAT CAPACITIES OF SOLID
AND MOLTER FLUORIDE MIXTURES

by

W. D. Powers
G. C. Blalock

DATE ISSUED:

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A Division of Union Carbide and Carbon Corporation
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~iv- TRy

TABLE OF CONTENTS

Page

SKMARY.l'..‘O.'.‘.‘..O..O....Q".ll.Q.ll"‘.l.l‘fi.....'.l‘fl...O..I. l‘,

INTRODUCTION  « ¢ e ¢ e 000 vsosooosasonsssossssesssssssonssnssnssssnsaoss 5
EXPERTMENTAL METHOD . ¢ o < o 00 e eosvsssocsososessosssassasaoonsssascsosas 6
FXPERIMENTAL RESULTS .+ s eccasvesesnsesssssssssessassrasosacsnsacacses 10
DISCUSSION OF RESULTS. «eveserornsneocncnsasssesesensosnsosnsnenenens 14
FUTURE WORK. « « o o v s eesoasonossssonsssonssssasncsssssssnsassssssassnse 20
APPENDIX

Table 2
Enthalpies, Heat Capacities, and Heat of FusiOheseevsccossses 22

Table 3
Healt CaPaCitieS...............‘.................'..'.0.0.0.0. 27

Table 4
Enthalpies of Zirconium Fluoride Base Mixtures....eseececasse 29

Table 5
Enthalpies of Alkali Fluoride Base MiXtures....eoeevsecccesesce 30

Table 6
Experimental Enthalpies of Composition No. TOeeseesesesccsscon 51
'li
4

SUMMARY

The enthalpies and heat capacities of seventeen fluoride mixtures in
the liquid state have been determined using Bunsen Ice Calorimeters and
copper block calorimeters. The fluoride mixtures were composed of the
fluorides of two or more of the following metals: lithium, sodium, potas-
sium, beryllium, zirconium, and uranium. The enthalpies and heat capacities
of most of these mixtures were studied in the solid state also. Estimates
of the heat of fusion have been made. Genersl empirical equations have
been developed which represent the enthalpies and heat capacities of the

fluoride mixtures in the liquid and in the solid state.

 
-O-

I APy

INTRODUCTION

For a number of years the enthalpies and heat capacities of various
fluoride mixtures have been determined by the ORNL Physical Properties
Group for the purpose of predicting the heat transfer characteristics of
these mixtures. This report is a compilation of the data previously re-
ported in the form of memorenda. Equations have been formulated so that
the enthalpy and heat capacity may be predicted from the composition.

In a sense this is a progress report since these properties are being

determined presently for other fluoride salt mixtures.
 

EXPERIMENTAL METHOD

Samples of the fluorides heated to constant and uniform temperatures
were dropped into calorimeters. The differences between the heat contents
of the samples at the furnace temperature and at the final temperature of
the calorimeter were measured by the calorimeters. The derivative of the

~enthalpy with respect to temperature yielded the heat capacity.

The design of the furnaces and of the Bunsen Ice Calorimeters has
been described previously (1,2). A full description of the Copper Block
Calorimeter will be given in a forthcoming ORNL report. During this in-
vestigation both apparatuses have been modified from time to time. The
brief descriptions which follow describe the apparatuses used at present.

The samples of the fluorides were contained in tapered metal cap-
sules, 2 1/2 inches long and 1 l/h inches average diameter. The capsules
were sealed by heliarc welding in an inert gas filled drybox to avoid
possible contamination with water, oxygen, and carbon dioxide.

Capsules containing the samples were heated in 6 inch long silver
liners centered in tube furnaces 2L" long. The temperatures of the
furnaces were measured by platinum - platinum-rhodium thermocouples lo-
cated in the silver liners and were held at the desired level by "Simply-
trol" controllers. After the capsules had reached the temperature of the

furnace, they were dropped into the calorimeters by electrically fusing

m“
£
i

#
%

the short pieces of wire on which they were suspended in the furnaces.
This process of heating a sample and dropping it into the calorimeter will
subsequently be referred to by the descriptive work "drop".

In the Bunsen Ice Calorimeter the heat liberated by the ssample in cool-
ing from the temperature of the furnace to that of the calorimeter melted
some of the ice in an ice-water mixture. The change from ice to water was
accompanied by a volume change which was measured by a system of buretis
connected to the calorimeter. Each milliliter change was equivalent to
878.7 calories.

The total amount of heat measured by the ice calorimeters varied from
1,000 to over 30,000 calories. It was found that the precision of the
measurements was significantly less when large amounts of heat were liber-
ated. Although the ice calorimeter is in general a very precise device
(3,4), it is felt that when large amounts of heat are liberated, a non-
isothermal state can exist giving rise to poorer precision. A copper
block calorimeter was developed to remedy this difficulty; it was found
that this new calorimeter was characterized by far greater precision when
high quantities of heat were released than was the case for the ice calori-
meter. Two copper block calorimeters were placed into regular service,

which now yield data at a relatively high rate.
In the copper block calorimeter the heat liberated by the sample heated

8 large mass of copper. The temperature rise of the copper was measured by

 

an iron-constantan thermopile (12 junctions in the copper and 12 junctions
in an ice bath). The copper block was contained in a stainless.steel shell
which was submerged in a water bath. A potentiometer controller activated by
another thermopile maintained a zero temperature difference between the'ccpper
block and the water bath to minimize any heat exchange between the copper
block and its surroundings. The copper block was calibrated in terms of
calories per millivolt by meking "drops"” with aluminum oxide. The enthalpy
of aluminum oxide is well known (4). The precision of the calibration is
within + 0.5%.

The least squares method was used to determine an equation which repre-
sented the experimental data. The enthalpy determinations made using the
ice calorimeters exhibited enough scatter so that only a linear relationship
between the enthalpy and temperature was found to be significant; therefore,
the reported healt capacities were not temperature dependent. But the more
precise results obtained with the copper block calorimeter could be repre-
sented by a definite quadratic relationship. Thus the heat capacity was
temperature dependent.

The individual experimental enthalpy values that were obtained using a
copper block calorimeter for the drops of mixture No. 70 are listed in
Table 6 and are shown in Figure 1. The results are typical of those obtained

with the ORNL copper block calorimeter.
(Cal / gram )

HT‘ H35°c

Enthalpy

200

100

ORNL- LR-DWG

8215

 

O— ONE DETERMINATION

®~-TWO OR MORE DETERMINATIONS

|

 

 

 

 

 

 

 

 

 

 

 

 

 

-

 

100 200 300

Temperature °C

Temperature Vs Enthalpy, Mixture No 7O

Fig {1

 

| | | | | | A
400 500 600 700 800 900 y 00
EXPERIMENTAL RESULTS

The enthalpy and heat capacity equations obtained are listed in Table
2. The type of calorimeter used, the enthalpy and heat cepacity together
with the temperature range over which these properties were studied, and
the heat of fusion at the reported melting point (5)(6) are shown in this
table.

The enthalpies and heat capacities of a few salt mixtures have been
determined by other laboratories. A comparison between the results ob-
tained at ORNL and the outside laboratories are listed in Table 1. At
the National Bureau of Standards (7) the enthalpy of mixture No. 12 in
the liquid state between 454° and 900°C was found to be

Hp - Hyop = 15.0 + 0.4910T - 4.63 x 107272 cal./g.
and for mixture No. 40 in the liquid state between 520° and 900°C.
Hp - Hyog = 4.2 + 0.3137T ~ 3.765 x 107572 cal./g.
At the Naval Research Laboratory (8) the enthalpy of mixture No. 12
in the solid state between 30° and 455°C was found to be
Hp - Hzq0q = =799 + 0.264T + 7.25 x 10572 cal./g.
and in the liquid state between L550 and 900°C
Hp - HygOp = -32.98 + 0.7278T - 4.962 x 10741°
+ 0.381 x 10-613 - 1.199 x 10-10T4 cal./g.
In Table 1 7.99 cal. has been added to the enthalpies determined by the
Naval Research Lsboratory so that all enthalpies would have the same base

temperature of 0°C.

 
TABLE 1
Checks with Other lsboratories

Enthalpies cal./g. -
Heat Capacities cal./g. °C

Mixture No. 12

ORNL NBS NRL
Tempegature Jce Calorimeter

C Bp - B % Bp - B%e % By - By °p
100 25.5 .29 27.1 .278
200 5545 .31 55.7 293
300 87.5 «33 85.7 .308
400 121.5 .35 117.2 . 322
500 256.8 45 248.9 445 255.0 457
600 302.1 45 292.9 435 299.8 440
700 3074 .45 33%6.0 426 343%,2 429
800 392.7 45 378,.2 417 385,6 <420
900 438.0 45 419.4 408 427.2 411
Heusion 95.k T 99.0

Mixture No. 40
ORNL NBS ORNL
Tempegature Copper Block Ice Calorimeter

C HT - HooC cp HT - HOOC cp HT - Hooc cP
600 178.7 .266 178.9 « 269 182.7 .25
700 205.2 .266 205.3 .261 207.5 .25
800 231,8 .266 231.1 0253 232.,3 .25
900 258.3 .266 256.0 246 257.0 .25
The comparison shown indicates that the enthalpies obtained at ORNL
with the ice calorimeter differ from those of the other lsboratories by a
maximum of 5%, and heat capacities differ by a maximum of 10%. Only one

comparison is availaeble for the ORNL copper block calorimeter. The enthal-

 

pies deviate with a maximum of 1%. At 70000 the heat capacity differed by
2%; at the extremes in the tempersture range studied (the melting point
and 900°C) the heat capacity difference was as great as 8%.

Most of the mixtures studied were near eutectic composition, and melt-
ing took place isothermally or over a very narrow temperature range. One
mixture, No. 82, melted over a wide range of temperature (nv5750 to BMSOG),
Figure 2. This was a zirconium fluoride base mixture. The enthalpy of
the liquid compared favorably with the enthalpies in the liquid state of
the other zirconium base mixtures (Table 4). This indicated that there was
a heat of fusion similar in value to the other mixtures which was absorbed
in the melting process. Mixture No. 21 did not exhibit an isothermal
melting. This mixture was not studied in detail below the reported melt-
ing point. The melting behavior is believed similar to No. 82. The enthalpy
of the liquid was similar to the values of the other zirconium fluoride
mixtures.

One mixture, No. 3, containing 60 M% Bng, exhibited a glass-like
behavior. The BeF, mixtures resembled those of heat capacities (slopes of
enthalpy temperature curves) of the alkali fluoride mixtures. However, the
enthalpy of No. 3 in the liquid state is much lower than the liquid enthal-
pies of the other mixes (Table 5). Presumsbly there is little, if any,

heat of fusion.
(Cal /gram)

Enthalpy

Hy=Hjsec

300

200

100

ORNL-LR-DWG 8216

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

/7
/‘
A
o -
7
/
y,
o
P
| | | ]
100 200 300 400 500 600 700 800 900

Temperature °C

Temperature Vs Enthalpy, Mixture No 82
Fig 2

_Ol..
=11~

DISCUSSION OF RESULTS

It is of interest to find general relationships between the enthal-
Pies and heat capacities of the various fluorides. For most of the solid
elements the heat capacity at constant volume is equal to 3R or 6 cal./OC
per gram atom. The more modern theories of Einstein and Debye have the
same value as a limit which is reached st normal temperatures for most
elements (9). At constant pressure the heat capacities are found to be
greater, being about 6.4 cal./°C per gram atom (Dulong and Petit's law).
The Debye equation also predicts correctly the heat capacity of some com-
pounds, these being the compounds that crystallize in the cubic system.
The equation may be modified to predict compounds that do not crystallize
in the cubic lattice. In 1865 Kopp suggested that the molar heat capacity
of a compound is approximately equal to the sum of the atomic heat capac-
ities of 1its constituent elements.

In the case of liquid compounds which have no definite groups of
atoms or radicals, it has been found empirically that each gram atom con-
tributes approximately 8 cal./OC to the molar heat capacity of the com-
pound (10). In general if there are definite groupings of atoms (such as
in the Soha and OH ions), the average hest capacity will be less. In the
case of the hydroxides the average healt capacity in the liquid state is

7.0 cal./g. atom °C (2).
-]~

In order to find the contribution per gram atom the average molecular
weight and the average number of atoms per mixture are needed. The aver-
age molecular weight has been successfully used in correlating the densi-

ties of the liquid fluoride mixtures (11). The quantities are defined as

follows:
—=Z
M g xi Mi
¥ =%
N q xi Ni

where M = average molecular weight of mixture

N = average number of atoms per mixture
Mi = molecular weight of component

Ni = number of ions per component

x, = mole fraction of component

When the enthalpy of a mixture in units of calories per gram is multiplied
by fi/fi the product is the enthalpy per gram atom. The heat capacity per
gram atom may be found in the same way. Table 3 lists the heat cgpacities
per gram stom of all the mixtures investigated together with the values of
M, N, and M/N.

Figure 3 shows the relastionship between the heat capacity in gram units
in the liquid state and the factor M/N. In this figure with the logarithmic
scales the straight lines drawn represent the equation

(fi/fi)(gp) = const = qp

f

where c, = heat capacity, cal./g. °C

C heat capacity, cal./g. atom °C

p
Heat Capacity
Cal /gram®C

0.6

0.5

04

o
ol

o
n

0.1

10

_]3..

LR-DWG 821

ORNL-

® ALKALI FLUORIDE BASE
0 ZIRCONIUM FLUORIDE BASE

 

20 30 40

Average Molecular Weight _

Average Number Atoms
Fig 3

 

Zl =

50
-1l

 

-l

The fluoride mixtures may be correlated best by dividing them into two
groups: +those that contain zirconium fluoride, and those that do not.
The latter will be referred to as the alkali fluoride mixtures.
Zirconium Fluoride Mixtures

The enthalpies in cal,/g. etom of the zirconium base mixtures afe
listed in Table 4. Most of the mixtures studied in this group consist of
sodium and zirconium fluorides with a little or no uranium fluoride. The
following equations were developed to represent these mixtures (Nos. 30,
31, k0, L4k, T0O).

In the solid

Ep - B0, = ~123 + 5.37T + 0.81 x 107977 (1)
C, = 5.3T + 1.62 x 10707

5.86 at 300°C
and in the liquid
L

C5 = 9.51 - 2.0 x 1077

f

104 + 9.51T - 1.0 x 10~27° (2)

= 8.11 at 700°C
The enthalpies calculated by these equations are slso listed in Table k.
The enthalpies of Nos. 30, 31, 40, 4li, 70 are represented by these equa-
tions to within 2% and all the zirconium fluoride base materials to within
10%. The heat capacity of all zirconium fluoride base materials are repre-

sented to within 15% except for Mixture No. 33, with a heat capacity of
~15-

.
!lllll' ‘.llpmfi
' by st
¥

10.9 cal./g. atom °C. The cause of the high heat capacity of this mixture
is unknown. Since the temperature range in which this mixture was studied
in the liquid state was small (6100 - 9%0°C) and therefore subject to more
error, it is planned to check the énthalpy of this mixture with the more
accurate copper block calorimeter.

The heat of fusion of these mixtures varied between 1570 to 2040
calories per gram atom‘with an average of 1810 cal.

Alkali Pluoride Mixtures

 

The enthalpies in cal./g. atom of the alkali fluoride base mixtures
are listed in Table 5, Most of mixtures studied consist of alkali fluorides
with uranium fluoride. Two mixtures contain beryllium fluoride. The follow-
ing equations represent all these mixtures. |

In the solid,

ET - _I_{25Oc = =340 + 6«76‘11 (3)
cP = 6,76
and in the liquid
Hy = Hyo0 =6Hy - 1610 + 9.47T (W)
C_ = 9.47

P

Because the heat of fusion varied grestly (from O to 1970 cal,/go atom) the
heat of fusion had to be included in the equation representing the liquid

to give a satisfactory correlation. The enthalpies calculated by these equa~
-16-

 

tions are also listed in Table 5. For the solid state the enthalples cal-
culeted by the equations from 20000 and higher agreed within 10% except
for Mixture No. 3 at 300°C. This is the mixture that indicated formation
of a glass and therefore would be expected to deviate from the others.

The heat capacities of the solid agreed within 6% of the equation. In the
liquid the enthalpies observed agreed within 5% and the heat capacities

within 16%.

 
-17-

FUTURE WORK

I. The ORNL Physical Properties Group has suggested that the presence
of complex compounds might increase the heat capacity of the liquid. If
these complex compounds should be decomposed between the melting point
and the upper temperature at which the liquid will be used, the heat re-
quired for decomposition weuld increase the heat capacity of the ligquid.
At present various mixtures in the sodium fluoride-zirconium fluoride
system are being meésured to determine the relationship between heat
capacity and composition. Complex compounds are known to exist in the

solid state in this system.

II. The heat capacity of mixture No. 33 which is at variance to the
other zirconium fluoride mixtures will be measured using the more accur-

ate copper block calorimeter.

I1I. As new mixtures are developed, their enthalpies and heat capacities

will be determined.
10.

11,

-18-

 

REFERENCES

Redmond, R. F. and lones, J., "The Design and Construction of an Ice
Calorimeter," ORNL-104O, August, 1951.

Powers, W. D. and Blalock, G. C., "Enthalpies and Specific Heats of
Alkali and Alkaline Earth Hydroxides at High Temperatures,"”
ORNL~1653, January, 195k.

Ginnings, D. C. and Corruccini, R. J., "An Improved Ice Calorimeter,"
J. Research Nationsl Bureau of Standards, 38, 1947, pp 583.

Ginnings, D. C. and Corruccini, R. J., "Enthalpy, Specific Heat, and
Entropy of Aluminum Oxide from 0° to 900°C," J. Research National
Bureau Standards, 38, 1947, pp 593.

 

 

Barton, C. J., "Fused Salt Compositions," CF-54-6-6.
Barton, C. J., personal communication.

Douglas, T. B. and Logan, W. M., "Thermal Conductivity and Heat
Capacity of Molten Materials,” WADC Technical Report 53-201, Part IV,
January, 195.4.

Walker, B. E. and Ewing, C. T. and Williams, D. D., "Tenth Progress
Report," NRL Memorandum Report 387, November, 195k.

Glasstone, S., "Thermodynamics for Chemists,” D. Van Nostrand, 1947,
Pp 121.

Kelley, K. K., “Contributions to the Data on Theoretical Metallurgy
High Temperature Heat Content, Heat Capacity and Data for Inorganic
Compounds," Bureau of Mines, Bulletin 476, 1949.

 

Cohen, S. I. and Jones, T. N., "A Summary of Density Measurements on
Molten Fluoride Mixtures and A Correlstion for Predicting Densities
of Fluoride Mixtures," ORNL-1702, July, 195h.
Mixture

12

Calorimeter

Ice

Ice

Ice

Ice

Temperature
Oc

25094650

480°
520°-990°

240°-480°

530°
540°-1000°

280°.-1050°

60°-1454°

14540
475°-875°

TABLE 2

Enthalpies and Heat Capacities

Enthalpy

Heat Capacity = Cp

Heat of Fusion =AHy

Solid

Fusion

Liquid Hp - Hyog

Solid

Fusion
Liquid

Glass
Liquid

Solid

Fusion
Liquid

&= HT - H (cal./g.)

(cal./g. °C)

(cal./g.)
HT - H()OC = -5 + Oc219T
 cp = 0.22.
AHy = 21
= =35 + 0.325T-
cp = 0.32
HT - HbOC = -1 + O-lh9T
cp = 0.1l5
AHy = 30
Hp - Hpop = 13 + 0.230T
cp = 0.23
Bp - Hyog = =43 4+ 0.315T
Hy - Byog = -2.6 + 0.271T + 9.8 x 107972
cp = 0.27 + 19,6 x 10-57
= .33%0 at 3%00°¢C
DHe = 95
HT - Hyoq =30.3 +-0.453T
CP = OoLl'5

Menmo by: i'i

W. D. Powers
G. C. Blalock

CF 51-11-195

CF 51-9-64

-6{-

CF 51-11-195

CF 54-5-160

CF 53=T7-200
Mixture

14

2l

31

33

*See discussion page 12

Calorimeter

Ice

Ice

Ice

Copper

Copper

Ice

Temperature

90°.450°

4520
500°-1000°

510°-890°
340°-500°

5200
540°-8940

54°.1488°

510°
546°-899°

280°-610°

TABLE 2 (Con't.

)

Enthalpy = Hp - H (cal./g.) Memo by:
Heat Capacity = c (cal./g. °C) W. D. Powers
Heat of Fusion =A§f (cal./g.) G. C. Blalock '
Solid Hp - Hgog = -9 + 0.310T
cp = 0.31
Fusion ANHr = 88
Liquid Hp - Hyop = 21 + 0.437TT CF 53-5-113
cp = O.uh
Liquid* Hp - HOOC = =-14.5 + 0.277T CF 52=-11-103
cp = 0.28
Solid Hp - Hpsog = -18.0 + 0.215T
cp = 0.22
Fusion NHy = 56

Liquid Hp - Hpsog = -3.3 + 0.3178T - 4.28 x 10”°1° CF 55-5-87

cp = 0.3178 - 8.56 x 10”71 5%
= 0.258 at 700°C
Solid Hy - HpgOp= il 4 0.1798T + 2.69 x 107°T° CF 55-5-87
cp = 0.1798 + 5.38 x 10777 |
= 0.196 at 300°C
Fusion AHp = 60.8 -
Liquid Hy ~ Hpsog= -9.8 + 0.3508T - 5.39 x 10"5@2
cp = 0.3508 - 10.79 x 107°T
= 0.275 at 700°C
Solid Hp - Hyop = -17.7 + 0.166T CF 53-11-128

i
Mixture

35

39

Lo

L

70

Calorimeter

Ice

Tce

Ice

Copper

Ice

Copper

Temperature

610°
610°-930°

90°-610°

610°
653°-924°

70°-5200

520°
571°-884°

260°-490°

540°
590°-9200

137°-503°

530°

TABLE 2 {Con't.)

Enthalpy = Hp - H (cal./g.)

Heat Capacity = cp (cal./g. °C)

Heat of Fusion = AHy (cal./g.)

Fusion AHf = 42

Liquid Hr - Hyog = -39.0 + 0.270T
Cp = 0.27

Solid Hp - Hpog = =2.9 + 0.17ET
ep = 0.17

Fusion AHp = 42

Liguid Hp - Hpog = 22.3 + 0.199T
cp = 0.20

Solid Hp - Hpsoc= ~4.6 + 0.182T
cp = 0.18

Fusion AHf = 63

Liquid HT - Hpgog= 14.8 + 0.2656T
cp = 0.266

Solid Hp - Hgog = =4.1 + 0.189T
cp = 0.19

Fusion AHr = 63

Liquid Hp - Hyog = 34.5 + 0.235T
cp = 0.24

Solid By - Hpgog= -2.7 + 0.1596T + 5.15 x 10777
cp = 0.1596 + 10.29 x 107°T

= 0,190 at 300°
Fusion AHr = 57

Memo by: ,:
W. D. Powers
G. C. Blalock

CF 53-11-128

CF 54-8-135

CF 54-10-140

CF 55-5-87 ;.'“3

CF 54-5-160

CF 55-5-88

 
w2t i i

Mixture Calorimeter
70 Copper
82 Copper

101 Ice
102 Copper

*¥See discussion page 12

Temperature

5670-892°

980-363°

582°.-900°

97°-594°

645°

655°-916°

107°-L466°

o2
532°-893°

TABLE 2 (Con't.)

Enthalpy = Hmp
Heat Capacity = cp

Heat of Fusion = AHr

Liquid

Solid*

Liquid

Solid

Fusion

Liquid

Solid

Fusion
ILiquid

Hy - Hosog=
CP=

i

Hp - Hpsog=
CP=
Hp - Hpgoc=
Cp =

Hp - Hyog =

Cp"“

Hp - Hpgoc=
CP =

- H (cal./g.)
(cal./g. ©C)
(cal./g.)

Memo by:
W. D. Powers
G. C. Blalock '
2.2 + 0.3033T - 3.24 x 10°°T° CF 55-5-88
0.3033 = 6.47 x 10771
0.258 at 700°C
9.5 + 0,230k + 4.07 x 10777°
0.2304 + 8.14 x 107°T
0.255 at 300°
-25.9 + 0.43LLT - 7.42 x 107°7°
0.4314 - 14.85 x 107°T
0.327 at 700°C
0.227T + 17 x 107°7°
0.227 + 33 x 10771
0.326 at 300°C
56
-68.9 + 0.531T

CF 54-8-135

—88-

= 0.53

9.38 + 0.2817T + 3.82 x 10°o72  CF 55-8-8

0.2817 + 7.6h x 107°T

0.305 at 300°C

95

-30.85 + 0.5839T - 10.28 x 10~°T°
0.5839 - 20.56 x 10™°T

0.440 at 700°¢C

.
Mixture

103

 

Calorimeter

Copper

Temperature

127°-465°

500
56%°-882°

TABIE 2 (Con't. )

Enthalpy = Hp - H (cal./g.)
Heat Capacity = cp (cal./g. ©°C)
Heat of Fusion = AHp (cal.g.)

Solid  Hp - Hpgog= =5.8 + 0.234T + k.9 x 10777
0.234 + 9.7 x 107°T
0.263 at 300°¢C
Fusion AHp = 68
Liquid Hyp - Hpgog= =88.3 + 0.657T - 19.7 x 207717
cp = 0.657 - 39.3 x 10”71
= 0.382 at 700°C

Cp

i

*560°C is the reported melting point. The major break in the
enthalpy-temperature relationship is at 5000C (4 10°).

Memo by:

W. D. Powers

G.

C. Blalock

CF 55-5-88

_ga_
% ‘;(-Q‘}"e .
V5

Mixture

12

1h

2l

30

51

Component

NaF
BeFo
NaF
UF),
NaF
BeFo

LiF
NaF

LiF
NaF
UF),
NaF
ZrFy

NaF
ZrFy

NeF
ZxFY

Mole
Per cent

= =3
O PO
O OO

Ounivn 00O WMow

o

N E R
>

° -

FRE O ERE QD
S rwor bho LEG

\n

=
L L—J . * -
Wk @ OO,

£\
‘4‘-7'0\0 \N
OO

\Nn AN
33
QO

TABLE 3
Heat Capacities

Average

Molecular

Weight

M

525

121.01

85.82

41.29

kk,85

112. 12

110.48

10k.61

Averasge
Number
of Atoms

2‘11'80

2.825

3.050

2.000

2,033

3.355

5.500

3.500

Ragio

 

=1

30.34

Lo,83

28.14

22,06

55,40

51.57

29.89

C
Cal./g.Patom °c
~Liguid

700°¢

Solid

300°

6.6k

6.38

6.81

6.84

5.86

9.86

9.85

8.86

9.35

9.6k

9.26

8.15

8.22

—-1-(8..

 
TABIE 3 (Con't.)

 

Mixture Component Mole Average Average Ratio D
Per cent Molecular Number % cal./g. atom °C
Weight of Atoms Solid Liquid
? T i N 300° 700°¢
i 33 NaF 50.0 141,32 3,500 40.38 6.70 10.90
ZxF) 25.0
UFY 25,0
39 NaF 65.0 115.20 3.050 37.77 6.50 7.52
ZrF), 15.0
UFy, 20.0
40 Nal 53,0 106.73 3.410 31.30 5.70 8.33
ZrF 43.0
UF), L.o
Ly NeF 53.5 109.77 3.395 32,33 6.11 7.60
ZrF), L0.0
UF), 6.5
70 NaF 56.0 104 .4y 3,320 31.46 5.98 8.12
ZrF), 39.0
UFY 5.0
82 LiF 55.0 70435 2,750 25,58 6.52 8.36
NaF 20.0
ZrFl 21.0
UFy, 4.0
101 LiF 57.6 43,63 2.120 20.58 6.71 10.93
NaF 38.4
UF), 4.0
102 LiF 50.0 42.02 2.000 21.01 6.41 9.2k
KF 50.0
103 LiF 48.0 52.90 2.120 24,95 6.56 9.53
KF 48.0
UF'k 4.0

_ga-
Mixtures

No. 30

No. 31

Composition (Mole Percent)

LiF
]

3,

Temperature

100
200
300
400
500
600

500
600
700
800
900

50.0

46.0
u’OO

2150
2830

5430
6250
7060
7830

1780

50.0

50.0

410
970
1550
2150
2760

5420
6260
TO60
7840

1820

*See discussion page 12

No. 40

55.0

43.0
L.0

430
1000
1570
2140
2710

5460

6290
7120

7950

' TABLE 4
Enthalpies of Zirconium Base Mixtures

No. 4k No. T0 Equations
(1) (2)
53.5 56.0
40.0 39.0
6.5 5.0
Enthalpy (cel./g. atom) = Hy -~ Hpsog
Solid
430 420
980 980
1550 1570 1560
21.60 2180 2150
2770 2830 2760
Liquid
5520 5420 5450
6280 6250 6270
TO40 7050 7070
7800 7830 7850
Heat of Fusion (cal./g. atom)
2040 1790

1970

No. 82

33
C O

o

-
oo

980
1620
2870%
L1LO%*

5270
6130
6950
1730

No. 21

£\
WO
oW H ™

3940%*
4860
5790
6720
T640

No. 33

50.0

25.0
25.0

1190
1860

2530
3200

5950
7040

8130

1700

No. 39

65.0

15.0
20.0

380
1030
1680
2330
2980
3620

5940
6690
7440

1570

—98.—
Mixture No. 2 No. 12
Composition (Mole Percent)
LiF
NeF 6.5
KF 26.0
BeFo
UFy, 27.5
Temperature
100°¢ %00
200 1010
300 1730 1670
400 2370 2370
500 3010
600
500 5160
600 5180 6090
700 6160 7020
800 7150 T960
900 8130 8890
1290 1970

¥The heat of fusion is to be added to these values.

46.5
11.5
42.0

TABLE 5

Enthalpies of Alkali Fluoride Base Mixtures

No. 14 No. 101 No. 102
44,5 57.6 50.0
10.9 38.4
43.5 50.0

1.1 4.0

No. 103 No. 1 No. 3
48,0
76.0 25.0
48.0
12.0 60.0
k.0 12.0 15.0

Enthalpy Hp - Hosoc (cal./g. atom)

Solid
360 380 400
1040 950 1020
1730 1590 1650
2410 2290 2300
3070
3910
Liquid
5170 4950
6140 5940
7100 6110 6880
8070 7200 7780
9030 8290 8640

Heat of Fusion (cal./g. atom)
1160

1940

1960

450
1070
1720 1680 1330
2390 23550 2220
3080 |
glass
3720 3100
5860 4700 3990
6860 5690 4870
T760 6670 5760
8570 7660 6650
1690 640 glass

Equations

(3) (&)

340
1010
1690
2360
3040
3720

3100%
LOTO*
5020%
5970%
6910%

qLam
-D8-

TABIE 6
Experimental Enthalpies - Mixture No. 70

Enthalpy
By - H35%, cal./s.
Enthalpy

Capsule Temperature °c Observed Calculated Difference
7 102 137 18.0 18.6 -0.6
Z 101 137 18.0 18.6 -0.6
7 101 137 18.3 18.6 -0.3
7 101 211 32,2 31.7 0.5
7 102 211 33,2 31.7 1.5
7 101 211 33,6 31.7 1.9
Z 101 234 35,4 35.9 -5
Z 101 237 35,4 36.5 ~1.1
7 102 237 36,2 36,5 ~0.3
7 101 25k 39.4 39.6 ~-0,2
7 102 254 40.3 39.6 0.7
7, 102 30k 49.3 49.0 0.3
7 101 308 L8,k 49.8 1.4
7 102 358 58.8 59.5 «0.7
7 101 358 59 .4 59.5 «0.1
7 101 360 60.4 59.9 0.5
7 102 393 66.3 66.k4 <0.1
7 101 393 66.4 66.4 0.0
7 101 450 17.7 78.0 wQe3
7 101 502 88.8 88.8 0.0
7 102 ' 502 88.8 88.8 0.0
2 101 503 89.6 89.0 0.6
7 102 528 112, b*

7 101 531 125, T*

7 102 555 156,0%

Z 101 555 157, 4*

7 101 559 158, L%

Z 102 567 162.0 162.1 -0.1
z 101 567 162,2 162.1 0.1
7 101 589 167.5 168.0 -0.5
Z 101 589 167.8 168.,0 =0,2
7, 102 590 167.9 168.2 -0.3
7 102 592 168.6 168.8 0.2
7 101 504 169.6 169,73 0.3
Z 101 643 183.4 182.2 1.2
7 102 646 184.0 183.0 1.0
7 102 690 19h.1 19k, k4 -0.3
Z 101 692 195.1 194.9 0.2
7 101 695 194,6 195.7 -1.1
Z 101 4T 208,.2 209.0 -0.8
-G~

TABLE 6 (Con't.)

Enthalpy
Hp - H35°C’ cal./g.

Enthalpy
Capsule Temperature S¢ Observed Calculated Difference
7 102 4T 208.4 209.0 -0.6
7 101 47 209.7 209.0 0.7
7 101 797 222.0 221.7 0.3
7 101 798 222,3 222.0 0.3
7 102 798 221.6 222.0 ~0.h4
7 101 849 234 ,8 234, T 0.1
7 101 850 234 .8 235.0 -0.2
Z 102 850 235,8 235.0 0.8
Z 102 886 24,2 243.8 0.4
Z 101 888 245,0 24k, 3 0.7
7 102 890 243,2 24}, 8 ~1.6
7 101 892 245,6 24h5.3 0.3

*These values not used in least squares analysis.