Solubility System: Sodium formate with Sodium tetraborate and Water
Components:

(1) Sodium formate, NaCHO2; [141-53-7] NIST WebBook
(2) Sodium tetraborate, Na2B4O7; [1330-43-4] NIST WebBook
(3) Water, H2O; [7732-18-5] NIST WebBook

Original Measurements

Berniyazova, D. G.; Kalacheva, V. G.; Schwartz, E. M.; Zh. Neorg. Khim. 31, 1045-8 (1986).

Variables:

Ambient temperature: Composition at 15 °C

Prepared by:

St. Trendafilova, St. Tepavitcharova

Method/Apparatus/Procedure:

The isothermal method was used. Equilibrium was achieved within 4 hours. The boron concentration was determined by titration with alkali using phenolphtalein and mannitol, after the sample had been evaporated to dryness, ignited at 60 °C and dissolved in boiling HCl.1 The formate content was determined from the carbon content by ignition. The composition of the solid phases was determined by the Schreinemakers' method.

Source and Purity of Materials:
  1. p.a. grade NaCHO2 and suprapure grade Na2B4O7 were used.
Estimated Errors:

Mass concentration (m/v) (1): Solid phase B is probably NaCHO2·2H2O.

References

1 Knipovich, Yu. N.; Morachevskii, Yu. V.; Analysis of Mineral Ores, 3rd ed., (L. Gostechizdat, p. 281, 1959).

Experimental Values:
Solubility values in the NaCHO2-Na2B4O7-H2O system at 15°C.
100w2 100w1 m2 (mol/kg)a m1 (mol/kg)a Phase (s)b
2.79 - 1.4 x 10-1 - A
2.73 6.14 1.5 x 10-1 9.9 x 10-1 A
2.53 12.63 1.5 x 10-1 2.19 A
2.47 18.24 1.5 x 10-1 3.38 A
2.24 20.52 1.4 x 10-1 3.91 A
2.04 24.16 1.4 x 10-1 4.81 A
1.94 25.35 1.3 x 10-1 5.13 A
1.59 29.52 1.1 x 10-1 6.3 A
1.47 31.52 1.1 x 10-1 6.92 A
1.23 35.21 1.0 x 10-1 8.15 A
1.17 37.88 1.0 x 10-1 9.14 A
1.09 39.26 9 x 10-2 9.68 A
9.8 x 10-1 39.98 8 x 10-2 9.96 A
8.6 x 10-1 40.64 7 x 10-2 10.22 A + B
6.3 x 10-1 40.56 5 x 10-2 10.14 B
- 41.82 - 10.57 B

(a) These values were calculated by the compilers. (b) The solid phases are: A = Na2B4O7ยท10H2O; B = NaCHO2.

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