ORNL-2106 - the Molten Salt Energy Technologies Web Site

of this reaction will be made at the conclusion of
the experimental work.
Experimental work is now in progress at 575OC.
Efforts will be made to extend the NiF, concen-
tration ranges and to obtain the temperature de-
pendence of the equilibrium. Particular attention
will be given to the determination of the activity
of NiF, in the saturating phase.
SOLU 6 ILI TY AN D STA B ILI TY 0 F STR UCTU RA L
METAL FLUORIDES IN MOLTEN NaF-ZrF,
J. D. Redman
The results of studies of the stability and solu-
bility of GF, in NaF-ZrF, (53-47 mole %) at
60OoC were presented previously. From these
experiments it was concluded that the solubility
of CrF, increased as the zirconium-to-chromium
ratio decreased, and, accordingly, the solubility
of GF, in this solvent was a function of the
amount of CrF added. It was postulated that the
change in soluiility was due to the separation of
CrF,*ZcF, as the solid phase, with a resultant
increase in the NaF concentration in the melt.
Some of these experiments have been rerun in order
to obtain more precise values at the larger zirconium-
to-chromium ratios, and the values thus obtained,
along with some of the earlier ones, are given in
Table 2.2.7.
14J. D. Redman, ANP Quar. Prog. Rep. Dec. 10, 195X
ORNL-2012D p 88.
PERfOD ENDING JUNE 10, 1926
Similar studies have been carried out on the
solubility of FeF, and NiF, in this solvent, and
the data are presented in Tables 2.2.8 and 2.2.9,
respectively. The data for these three structural
metal fluorides also are plotted on Fig. 2.2.3.
An examination of the data presented for 600OC
shows that the solubility of CrF, increases quite
rapidly as the zirconium-to-chromium ratio de-
creases over the entire range studied. A less
pronounced effect is noted for FeF,, and in the
case of NiF, a slight increase is observed for
the higher zirconium-to-nickel ratios. At the lower
zirconium-to-nickel ratios the solubility is con-
stant. These differences in behavior are shown
quite clearly in Fig. 2.2.3. It appears that the
solid phases present for the CrF, and FeF, sys-
tems contain ZrF,, probably as MF2*ZrF4, whereas
the solid phase in the NiF, system appears to tie
up only very small amounts of ZrF,. It may be
noted that at 800OC the solubility of NiF, is inde-
pendent of the zirconium-to-nickel ratio, which
suggests that the solid phase present is NiF,.
There is some question regarding the reliability
of the data given in the zirconium-to-sodium ratio
columns in the tables, but for GF, and for FeF,
at 600OC it is believed that the decrease in the
ratio as the excess of metal fluoride added was
increased is real. The ratio of zirconium to sodium
is 0.88 in the starting material, and the consider-
ably lower values found for the large additions of
TABLE 2.2.7. SOLUBILITY AND STABILITY OF CrFZ IN MOLTEN NaF-ZrF4 (53-47 MOLE %) AT 60O0C
Conditions of
Equi li kation
Found in Filtrate
Cr ++ Zr-tcuCr Zr Na Zr-to-Na F G++ Total G
(wt %) Ratio' (wt %) (wt %) Ratio* (wt (wt X) (wt %I
1.4 17 41.5 13.3 0.79 45.3 0.66 0.73
1.4 17 41.3 13.4 0.78 44.8 0.65 0.83
4.0 5.8 39.8 12.7 0.79 45.1 2.1 1.9
4.0 5.8 ' 39.5 129 0.78 45.2 20 1.9
6.4 3.4 38.4 13.6 0.71 44.8 3.5 3.5
6.4 3.4 38.9 141 0.70 44.3 3.4 3.6
9.6 21 37.9 13.8 0.69 44.0 5.0 5.2
9.6 2.1 36.3 13.4 0.68 44.2 5.7 59
'Ratio calculated from mole fractions.
101