Handbook of Solvents - George Wypych - ChemTech - Ventech!

1494 Victor Cherginets
Oxide CsCl-KCl-NaCl (0.45:0.25:0.30) CsBr-KBr (0.66:0.34) CsI
Cu2O 6.95±0.10 6.35±0.05
ZnO 8.80±0.07 8.15±0.03 11.03±0.16
CdO 7.54±0.48 7.09±0.05 9.35±0.16 8.00±0.06
SnO 11.28±0.05
PbO 8.21±0.05 7.04±0.05 8.52±0.07 7.80±0.10
21.3.4 ON THE POSSIBILITY TO PREDICT OXIDE SOLUBILITIES ON THE
BASE OF THE EXISTING DATA
Studies 33,59-62 show that the estimation of oxide solubilities in non-studied halide melts are
possible, at least, for 1:1 oxides, i.e., MeO.
21.3.4.1 The estimation of effect of anion
It has been found that oxide solubilities (pP) are related to cation radius. 33 For Na- and
K-based halide melts, a plot for solubility products expressed in molar fractions is described
by the following equation:
−2
pP = pP + ar 2 +
N N,0 Me
[21.3.20]
where:
r 2+ the cation of oxide radius, nm.
Me
The value of a is ~0.053 and values of pPN,0 are 1.8, 3.2 and 2.6 for chloride, bromide
and iodide melts, respectively. The accurate values are presented in Table 21.3.4.
Table 21.3.4. Coefficients of plots [21.3.20] for molten alkaline halides at the
confidence level 0.95. After references [38,59-62]
Melt t, o C pPN,0 a
KCl-NaCl 700 1.8±0.9 0.053±0.01
CsCl-KCl-NaCl 600 1.7±2.0 0.057±0.01
CsCl-KCl-NaCl 700 1.7±0.3 0.054±0.02
CsBr-KBr 700 3.2±1.8 0.053±0.01
CsI 700 2.65±0.58 0.052±0.01
21.3.4.2 The estimation of effect of melt acidity
Papers 25,26,57,58 give us the possibility to estimate the oxide solubilities for melts with cations
more acidic than Na + . For acidic melts the following equation applies:
pP = pP −pI
N N, KCl−NaCl I
[21.3.21]
where pI l is ~3.5 for KCl-NaCl, ~2 for SrCl 2-KCl-NaCl, ~4 for CaCl 2-KCl-NaCl and ~1,8
for BaCl 2-KCl. If the composition of acidic cation is different from that of melts described
in the previous section the value pI l in [21.3.21] can be corrected as follows: