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IUPAC-NIST Solubility Database
NIST Standard Reference Database 106
Solubility System:
Cobalt formate with Zinc formate and Water
Components:
(1) Cobalt formate; Co(CHO2)2; [544-18-3]
NIST Chemistry WebBook
for detail
(2) Water; H2O; [7732-18-5]
NIST Chemistry WebBook
for detail
(3) Zinc formate; Zn(CHO2)2; [557-41-5]
NIST Chemistry WebBook
for detail
Original Measurements:
Balarew, C.C.; Vassileva, V.Z., Compt. Rend. Acad. Bulg. Sci. 43, 51-4 (1990).
Variables:
Concentration = Composition at 25 ºC
Prepared By:
Chr. Balarew and St. Trendafilova
Experimental Data:
(Notes on the Nomenclature)
(Please see footnotes following the table(s).)
Solubility values in the Co(CHO
2
)
2
-Zn(CHO
2
)
2
-H
2
O system at 25 °C.
Chemical
1
Phase
Mass Fraction w
1
m
1
[mol kg-1]
a
Chemical
2
Mass Fraction w
2
m
2
[mol kg-1]
a
Solid Phase(s)
b
Distribution Coefficient
Zn2+/Co2+
Distribution Coefficient
Co2+/Zn2+
Co(CHO2)2
Liquid
2.44
0.168
Zn(CHO2)2
---
---
A
---
---
Co(CHO2)2
Liquid
1.88
0.130
Zn(CHO2)2
0.73
0.048
B
0.53
1.89
Co(CHO2)2
Liquid
1.71
0.118
Zn(CHO2)2
1.32
0.088
B
0.52
1.92
Co(CHO2)2
Liquid
1.43
0.099
Zn(CHO2)2
1.81
0.120
B
0.47
2.13
Co(CHO2)2
Liquid
1.05
0.073
Zn(CHO2)2
2.00
0.174
B
0.46
2.17
Co(CHO2)2
Liquid
0.86
0.060
Zn(CHO2)2
2.92
0.195
B
0.45
2.22
Co(CHO2)2
Liquid
0.75
0.052
Zn(CHO2)2
3.25
0.218
B
0.48
2.08
Co(CHO2)2
Liquid
0.50
0.035
Zn(CHO2)2
3.83
0.258
B
0.53
1.89
Co(CHO2)2
Liquid
0.27
0.019
Zn(CHO2)2
4.65
0.315
B
0.51
1.96
Co(CHO2)2
Liquid
---
---
Zn(CHO2)2
5.38
0.366
C
---
---
Notes:
a
The molality values were calculated by the compilers.
b
The solid phases are: A = Co(CHO
2
)
2
•2H
2
O; B = (Co,Zn)(CHO
2
)
2
•2H
2
O; C = Zn(CHO
2
)
2
•2H
2
O.
Method/Apparatus/Procedure:
The method used was the isothermal decrease of supersaturation, for 15-20 hrs. The CO
2+
content of the liquid and solid phases was determined complexometrically using Complexon III at
p
H 5.5-6 with Xylenol Orange as indicator after removing Zn
2+
with an ion exchange resin. The sum of CO
2
+ and Zn
2+
was determined complexometrically by back titration with ZnSO
4
at
p
H 5.5-6.0 using Xylenol Orange as indicator. The composition of the suction-dried mixed crystals was determined by the algebraic indirect identification of the solid phase composition method.
1
Source and Purity of Materials:
The reagents used were of p.a. grade. Cobalt and zinc formates were prepared by the action of dilute formic acid with cobalt and zinc normal or basic carbonates, respectively.
Estimated Errors:
Solubility: The solubility of the salts was determined in a slight excess of formic acid (about 2%) to suppress salt hydrolysis.
Temperature: Not given.
References:
1
D. Trendafelov and Chr. Balarew, Comm. Dept. Chem. Bulg. Acad. Sci.
1
, 73 (1968).