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IUPAC-NIST Solubility Database
NIST Standard Reference Database 106
Solubility System:
Magnesium formate with Iron formate and Water
Components:
(1) Iron formate; Fe(CHO2)2; [3047-59-4]
NIST Chemistry WebBook
for detail
(2) Magnesium formate; Mg(CHO2)2; [557-39-1]
NIST Chemistry WebBook
for detail
(3) Water; H2O; [7732-18-5]
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 Mg(CHO
2
)
2
-Fe(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
Mg2+/Fe2+
Distribution Coefficient
Fe2+/Mg2+
Fe(CHO2)2
Liquid
4.20
0.301
Mg(CHO2)2
---
---
A
---
---
Fe(CHO2)2
Liquid
2.68
0.193
Mg(CHO2)2
2.22
0.204
B
0.06
16.67
Fe(CHO2)2
Liquid
1.56
0.115
Mg(CHO2)2
5.38
0.506
B
0.05
20.00
Fe(CHO2)2
Liquid
1.21
0.090
Mg(CHO2)2
6.64
0.630
B
0.05
20.00
Fe(CHO2)2
Liquid
0.78
0.059
Mg(CHO2)2
8.30
0.798
B
0.05
20.00
Fe(CHO2)2
Liquid
0.49
0.037
Mg(CHO2)2
9.40
0.912
B
0.05
20.00
Fe(CHO2)2
Liquid
0.25
0.019
Mg(CHO2)2
10.79
1.061
B
0.04
25.00
Fe(CHO2)2
Liquid
0.19
0.015
Mg(CHO2)2
11.06
1.090
B
0.04
25.00
Fe(CHO2)2
Liquid
0.13
0.010
Mg(CHO2)2
11.69
1.159
B
0.05
20.00
Fe(CHO2)2
Liquid
---
---
Mg(CHO2)2
11.96
1.188
C
---
---
Notes:
a
The molality values were calculated by the compilers.
b
The solid phases are: A = Fe(CHO
2
)
2
•2H
2
O; B = (Fe,Mg)(CHO
2
)
2
•2H
2
O; C = Mg(CHO
2
)
2
•2H
2
O.
Method/Apparatus/Procedure:
The method used was the isothermal decrease of supersaturation in an argon atmosphere for 15-20 hrs. The Fe
2+
content of the liquid and solid phases was determined complexometrically using Complexon IV at
p
H 1.5 with sulfosalicylic acid as indicator after first oxidizing Fe
2+
with hydrogen peroxide. The sum of Fe
2+
and Mg
2+
was determined by back titration with ZnSO
4
in an excess of Complexon IV at
p
H 9.5-10 using Eriochrome Black T 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 "pro analysis" grade. Mg(CHO
2
)
2
was prepared by neutralizing dilute formic acid with basic or normal magnesium carbonate. Fe(CHO
2
)2 was prepared by dissolving powdered Fe in dilute formic acid.
Estimated Errors:
Solubility: The solubility of the salts was determined in a slight excess of formic acid (about 2%) to suppress salt hydrolysis.
References:
1
D. Trendafelov and Chr. Balarew, Comm. Dept.Chem. Bulg. Acad. Sci.
1
, 73 (1968).