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IUPAC-NIST Solubility Database
NIST Standard Reference Database 106
Solubility System:
Iron(II) formate with Zinc formate and Water
Components:
(1) Iron(II) formate; Fe(CHO2)2; [3047-59-4]
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.; Stoilova, D.; Vassileva, V., J. Solid State Chem. 57, 260-6 (1985).
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 Fe(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
Fe2+/Zn2+
Distribution Coefficient
Zn2+/Fe2+
Fe(CHO2)2
Liquid
4.20
0.301
Zn(CHO2)2
0.00
0.00
A
---
---
Fe(CHO2)2
Liquid
3.72
0.267
Zn(CHO2)2
0.78
0.053
B
0.92
1.09
Fe(CHO2)2
Liquid
3.09
0.222
Zn(CHO2)2
1.53
0.103
B
1.00
1.00
Fe(CHO2)2
Liquid
2.36
0.170
Zn(CHO2)2
2.37
0.160
B
0.94
1.06
Fe(CHO2)2
Liquid
1.52
0.110
Zn(CHO2)2
3.33
0.225
B
1.18
0.85
Fe(CHO2)2
Liquid
1.07
0.078
Zn(CHO2)2
4.04
0.274
B
1.09
0.92
Fe(CHO2)2
Liquid
0.64
0.046
Zn(CHO2)2
4.52
0.3067
B
1.08
0.92
Fe(CHO2)2
Liquid
0.00
0.00
Zn(CHO2)2
5.38
0.3659
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,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, under stirring, for 15-20 h in an argon atmosphere to prevent oxidation of Fe
2+
. The Fe
2+
content of the liquid and solid phases was determined complexometrically at
p
H 1.5 using Sulfosalicylic acid as indicator after preliminary oxidation of Fe
2+
by H
2
O
2
. The sum of Fe
2+
and Zn
2+
was also determined complexometrically at
p
H 5.5 using Xylenol Orange as indicator after first oxidizing the Fe
2+
with H
2
O
2
. The composition of the suction-dried mixed crystals was determined by the algebraic indirect identification of the solid phase composition method.
1
They were also studied by x-ray diffraction.
Source and Purity of Materials:
The reagents used were of p.a. grade. Zinc formate was prepared by the action of dilute formic acid with zinc basic carbonate. The iron formate was prepared by dissolving powdered iron 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).