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IUPAC-NIST Solubility Database
NIST Standard Reference Database 106
Solubility System:
Potassium formate with Cobalt formate and Water
Components:
(1) Potassium formate; KCHO2; [590-29-4]
NIST Chemistry WebBook
for detail
(2) Cobalt formate; Co(CHO2)2; [544-18-3]
NIST Chemistry WebBook
for detail
(3) Water; H2O; [7732-18-5]
NIST Chemistry WebBook
for detail
Original Measurements:
Portnova, S.M.; Petrova, E.V.; Lyashchenko, A.K.; Lepeshkov, I.N., Zh. Neorg. Khim. 28, 2952-7 (1983).
Variables:
Concentration = Composition at 25 ºC
Prepared By:
Chr. Balarew and St. Trendafilova
Experimental Remarks:
The molality values were calculated by the compilers.
Comment:
These same data, expressed as mol %, are published in :E. V. Petrova, A. K. Lyashchenko, A. F. Borina, and S. M. Portnova, Zh. Neorg. Khim.
28
, 3158-63 (1983).
Experimental Data:
(Notes on the Nomenclature)
(Please see footnotes following the table(s).)
Solubility values in the KCHO
2
-Co(CHO
2
)
2
-H
2
O system at 25 °C.
Chemical
1
Phase
Mass Fraction w
1
m
1
[mol kg-1]
Chemical
2
Mass Fraction w
2
m
2
[mol kg-1]
Solid Phase(s)
a
KCHO2
Liquid
---
---
Co(CHO2)2
2.42
0.166
A
KCHO2
Liquid
1.76
0.216
Co(CHO2)2
1.59
0.110
A
KCHO2
Liquid
11.53
1.558
Co(CHO2)2
0.51
0.039
A
KCHO2
Liquid
15.64
2.216
Co(CHO2)2
0.46
0.037
A
KCHO2
Liquid
23.28
3.630
Co(CHO2)2
0.48
0.042
A
KCHO2
Liquid
33.86
6.149
Co(CHO2)2
0.68
0.069
A
KCHO2
Liquid
33.66
7.003
Co(CHO2)2
1.11
0.119
À+B
KCHO2
Liquid
37.35
7.260
Co(CHO2)2
1.49
0.163
B
KCHO2
Liquid
40.06
8.162
Co(CHO2)2
1.59
0.183
B
KCHO2
Liquid
46.78
10.79
Co(CHO2)2
1.67
0.217
B
KCHO2
Liquid
55.12
14.97
Co(CHO2)2
1.11
0.170
B
KCHO2
Liquid
57.49
16.46
Co(CHO2)2
0.99
0.16
B
KCHO2
Liquid
63.36
20.96
Co(CHO2)2
0.71
0.13
B+C
KCHO2
Liquid
74.48
34.75
Co(CHO2)2
0.02
0.01
C
KCHO2
Liquid
81.82
53.503
Co(CHO2)2
---
---
C
KCHO2
Liquid
43.64
9.512
Co(CHO2)2
1.82
0.224
A
KCHO2
Liquid
43.47
9.494
Co(CHO2)2
2.10
0.259
A+B
KCHO2
Liquid
53.12
14.04
Co(CHO2)2
1.90
0.284
B
KCHO2
Liquid
64.39
22.25
Co(CHO2)2
1.21
0.236
B
KCHO2
Liquid
71.21
30.31
Co(CHO2)2
0.86
0.21
B
KCHO2
Liquid
73.73
34.29
Co(CHO2)2
0.71
0.18
B
KCHO2
Liquid
76.33
39.10
Co(CHO2)2
0.46
0.13
B+C
KCHO2
Liquid
78.33
43.29
Co(CHO2)2
0.16
0.049
C
KCHO2
Liquid
80.38
49.05
Co(CHO2)2
0.14
0.048
C
Notes:
a
The solid phases are: A = Co(CHO
2
)
2
•2H
2
O; B = K
3
Co
2
(CHO
2
)
7
•2H
2
O; C = KCHO
2
.
Method/Apparatus/Procedure:
The isothermal method was used. Equilibrium was reached in 4 weeks. The potassium content of both phases was determined by the tetraphenylborate method.
1
The cobalt content was determined complexometrically by back titration with ZnSO
4
using Xylenol Orange in a urotropin medium as indicator.
Source and Purity of Materials:
Co(CHO
2
)
2
•2H
2
O was prepared from p.a. reagent grade cobalt nitrate by adding a KOH soln and then dissolving the Co(OH)
2
in a formic acid soln. KCHO
2
was prepared by neutralizing a 85% formic acid soln with dilute KOH. After crystallization the crystals were washed with ethanol and dried over H
2
SO
4
.
Estimated Errors:
Solubility: It is very strange to have supersaturated solution in equilibrium with the same crystal phases as these existing in equilibrium with the saturated solution.
References:
1
R. Pribil and D. Maricova, Chem. Listy
46
, 542 (1952).