Components:
(1) Sodium formate,
NaCHO2; [141-53-7]
NIST WebBook
(2) Sodium chloride,
NaCl; [7647-14-5]
NIST WebBook
Original Measurements
Leonesi, D.; Braghetti, M.; Cingolani, A.; Franzosini, P.; Z. Naturforsch. A 25, 52-5 (1970).
Variables:
Prepared by:
Method/Apparatus/Procedure:
A Pyrex device, suitable for work under an inert atmosphere, and allowing one to observe the system visually, was used (for details, refer to Ref.1. The initial crystallization temperatures were measured with a Chromel-Alumel thermouple checked by comparison with a certified Pt resistance thermometer, and connected to a L&N Type K-3 potentiometer.
Source and Purity of Materials:
- C. Erba RP materials, dried by heating under vacuum, were used.
Estimated Errors:
Ambient temperature: The compiler estimates the accuracy of the temperature measurements to be probably ±0.1 K.
Mass concentration (m/v) (1): No information is given.
References
1
Braghetti, M.; Leonesi, D.; Franzosini, P.; Ric. Sci. 38, 116 (1968).
2
Leonesi, D.; Piantoni, G.; Berchiesi, G.; Franzosini, P.; Ric. Sci. 38, 702 (1968).
Experimental Values:
Note: Note 1: In the original paper the results were shown in graphical form. The numerical values listed above were given in a personal communication from one of the authors (F.P.) to the compiler.Note 2: The system could not be investigated above 300°C due to thermal instability of the formate.
Note 3: There is a eutectic at 249.8°C and 100x2 = 5.15.
Note 4: Previous investigations by the same group2 stated that the cryometric constant of sodium formate was K = 9.4 ± 0.2 K molality-1, and that
(where ΔT is the experimental freezing point depression, and m is the molality of the solute) when NaCl was the solute. Consequently, the solubility of component (2) in component (1) in the solid state ought to be insignificant.
Melting temperatures for different mole fractions
| Tm (K) | Tm (°C) | 100x2 |
|---|---|---|
| 530.7 | 257.5 | 0.0 |
| 529.2 | 256.0 | 9.5 x 10-1 |
| 527.7 | 254.5 | 2.1 |
| 526.4 | 253.2 | 3.0 |
| 524.8 | 251.6 | 3.94 |
| 523.9 | 250.7 | 4.6 |
| 523.0 | 249.8 | 5.14 |
| 525.7 | 252.5 | 5.22 |
| 532.7 | 259.5 | 5.63 |
| 533.7 | 260.5 | 5.7 |
| 540.0 | 266.8 | 5.98 |
| 548.6 | 275.4 | 6.48 |
| 559.5 | 286.3 | 7.13 |
| 566.8 | 293.6 | 7.55 |
| 572.1 | 298.9 | 7.83 |
(a) The T/K values were calculated the compiler.
