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Solubility System: Magnesium formate with Iron formate and Water (Original Report)

Components:
(1) Magnesium formate, Mg(CHO2)2; [557-39-1] NIST Chemistry WebBook
(2) Iron(II) formate, Fe(CHO2)2; [3047-59-4] NIST Chemistry WebBook
(3) Water, H2O; [7732-18-5] NIST Chemistry WebBook
Original Measurements
Balarew, C. C. ; Vassileva, V. Z. ; Compt. Rend. Acad. Bulg. Sci. 43, 51-4 (1990).

Variables:
Concentration: Composition at 25°C
Experimental Data:
w1 m1 (mol/kg) [Note: $^a]Phase [Note: ^b]Phase
4.200.301ALiquid
2.682.220.0616.670.1930.204BLiquid
1.565.380.0520.000.1150.506BLiquid
1.216.640.0520.000.090.63BLiquid
0.788.300.0520.000.0590.798BLiquid
0.499.400.0520.000.0370.912BLiquid
0.2510.790.0425.000.0191.061BLiquid
0.1911.060.0425.000.0151.09BLiquid
0.1311.690.0520.000.011.159BLiquid
11.961.188CLiquid

a) The molality values were calculated by the compilers.
b) The solid phases are: A = Fe(CHO2)2·2H2O; B = (Fe,Mg)(CHO2)2·2H2O; C = Mg(CHO2)2·2H2O.

Method/Apparatus/Procedure:

The method used was the isothermal decrease of supersaturation in an argon atmosphere for 15-20 hrs. The Fe2+ content of the liquid and solid phases was determined complexometrically using Complexon IV at pH 1.5 with sulfosalicylic acid as indicator after first oxidizing Fe2+ with hydrogen peroxide. The sum of Fe2+ and Mg2+ was determined by back titration with ZnSO4 in an excess of Complexon IV at pH 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:

(1) The reagents used were of "pro analysis" grade. Mg(CHO2)2 was prepared by neutralizing dilute formic acid with basic or normal magnesium carbonate. Fe(CHO2)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).

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