Handbook of Solvents - George Wypych - ChemTech - Ventech!

630 Victor Cherginets
controlled titrant loss affecting experimental results. Ditto referred to all results obtained by
the reverse titration by MoO 3 and CrO 3 as the equivalence point.
Acidic properties of P V oxocompounds in the chloride melt at 700 o C were investigated
using a membrane oxygen electrode Ni,NiO|ZrO 2. 93 Polyphosphates of compositions with
Na 2O-P 2O 5 ratio from 1.67 to 3 formed in the acidic region:
− 2 n+
2
3−
PO + PO = P O
( ) − ( n+
5)
n 3n+ 1
4 n+ 1 3n+ 5
[10.4.43]
The corresponding constants were estimated. Polyphosphate solubilities were determined
by a cryoscopic method.
The titration of V 2O 5 proceed in two stages: 94
pK 9303 . . pK 8303 . .
VO ⎯⎯⎯⎯⎯→VO⎯⎯⎯⎯⎯→VO 2 5
=− ± − =− ± 4−
3
2 7
[10.4.44]
Some results of oxoacidity studies in molten KCl-NaCl were obtained in our
works, 95-99 they are presented in Table 10.4.1.
Table 10.4.1. The Lux acid-base equilibrium constants in molten KCl-NaCl and NaI (at
the confidence level 0.95) [After references 95,96,98]
Equilibrium
m
KCl-NaCl
-pK
N mol%
- 2−
4−
2PO3 + O = P2O7 8.01±0.1 10.67 6.67
− 2−
3−
PO3 + O = PO4
5.93±0.1 7.26 5.26
− 2−
3− 2−
PO3 + 2O = [ PO4 ⋅O]
7.24±0.1 - -
2−
2−
CrO3 + O = CrO4
8.41±0.1 9.77 7.77
2− 2−
2−
Cr2O7 + O = 2CrO4
7.18±0.1 7.18 7.18
2− 2−
2− 2−
2CrO4 + O = [2CrO4 ⋅O ]
1.60±0.2 4.26 0.26
2−
2−
MoO3 + O = MoO4
8.32±0.2 9.65 7.65
2−
2− 2−
MoO3 + 2O = [MoO4 ⋅O
]
9.71±0.3 11.37 7.37
2−
2−
WO3 + O = WO4
9.31±0.2 10.64 8.64
2−
2− 2−
WO3 + 2O = [WO4 ⋅O
]
10.67±0.5 13.33 9.33
2− 2−
−
BO 4 7 + O = 4BO2
4.82±0.1 2.16 4.16
− 2−
3−
BO2 + O = BO3
2.37±0.2 3.17 1.70
2−
−
VO 2 5 + O = 2VO3
6.95±0.2 6.95 6.95
2−
4−
VO 2 5 + 2O=
VO 2 7
12.23±0.1 14.89 10.89
2−
3−
VO 2 5 + 3O=
2VO4
12.30±0.1 14.96 10.96
2−
3− 2−
VO 2 5 + 5O= 2[VO4 ⋅O
]
13.88±0.5 19.20 11.20
2GeO
2−
2−
+ O = Ge O
4.18±0.4 6.84 2.84
2
2 5