SDS Volume (4630)
Volume 73. Metal and Ammonium Formate Systems, p None
Original Measurements
Balarew, C.; Stoilova, D.; Vassileva, V.; J. Solid State Chem. 57, 260-6 (1985).
Variables:
Room Temp: Composition at 25 °C
Prepared by:
St. Trendafilova, Chr. Balarew
Method/Apparatus/Procedure:
The method used was the isothermal decrease of supersaturation, under stirring, for 15-20 hrs. in an argon atmosphere to prevent oxidation of $\ce{Fe^{2+}}$. The $\ce{Fe^{2+}}$ content of the liquid and solid phases was determined complexometrically at pH 1.5 using sulfosalicylic acid as indicator after preliminary oxidation of $\ce{Fe^{2+}}$ by $\ce{H2O2}$. The sum of $\ce{Fe^{2+}}$ and $\ce{Co^{2+}}$ was also determined complexometrically at pH 5.5 using Xylenol Orange as indicator after first oxidizing the $\ce{Fe^{2+}}$ with $\ce{H2O2}$. 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. Cobalt formate was prepared by the action of dilute formic acid with cobalt basic carbonate. The iron formate was prepared by dissolving powdered iron in dilute formic acid.
Estimated Errors:
Ambient temperature: Not given.
Mass concentration (m/v) (1): The solubility of the salts was determined in a slight excess of formic acid (about 2%) to suppress salt hydrolysis.
References
1 Trendafelov, D.; Balarew, Chr.; Comm. Dept. Chem. Bulg. Acad. Sci. 1 , 73 (1968).
Components:
- Iron(II) formate, $\ce{ Fe(CHO2)2 }$; [3047-59-4] NIST WebBook
- Cobalt formate, $\ce{ Co(CHO2)2 }$; [544-18-3] NIST WebBook
- Water, $\ce{ H2O }$; [7732-18-5] NIST WebBook
Experimental Data
Solubility values in the Fe(CHO2)2-Co(CHO2)2-H2O system at 25°C.
| 100w1 | 100w2 | D1|2 | D2|1 | m1 (mol/kg) | m2 (mol/kg) | Phase (s) () |
|---|---|---|---|---|---|---|
| 4.20 | 0.00 | - | - | 0.301 | 0.00 | A |
| 3.51 | 0.44 | 0.62 | 1.61 | 0.251 | 0.031 | B |
| 2.47 | 0.97 | 0.59 | 1.70 | 0.175 | 0.067 | B |
| 2.01 | 1.25 | 0.61 | 1.64 | 0.142 | 0.087 | B |
| 1.51 | 1.57 | 0.54 | 1.85 | 0.107 | 0.109 | B |
| 1.17 | 1.74 | 0.56 | 1.79 | 0.083 | 0.120 | B |
| 0.90 | 1.79 | 0.49 | 2.04 | 0.063 | 0.123 | B |
| 0.51 | 2.45 | 0.52 | 1.92 | 0.036 | 0.169 | B |
| 0.00 | 2.44 | - | - | 0.00 | 0.168 | C |
(a) The molality values were calculated by the compilers.
(b) The solid phases are: A = Fe(CHO2)2·2H2O; B = (Fe,Co)(CHO2)2·2H2O; C = Co(CHO2)2·2H2O.
