THERMAL EXPANSION OF SODIUM AND POTASSIUM CHLORIDES FROM LIQUID-AIR TEMPERATURES TO +300° C.

Abstract

The thermal expansion coefficients of sodium and potassium chloride were measured from liquid-air temperatures to +300° C. The expansion coefficients of iron pyrites from liquid-air temperature to 0° C. and of rock-salt from room temperature to 300° C. are also reported.The Gruneisen constants for NaCI and KCI are shown to decrease with temperature. In potassium chloride the decrease is more rapid.A comparison of the lattice expansion coefficients and the macros copicexpansion coefficients of sodium and potassium chlorides has been made. The need for an accurate lattice expansion measurement of sodiumchloride at high temperatures is emphasised. In potassium chloride a systematic difference exists between the values of the author and the lattice expansion values of Glover. Though the experiments have been carried out on different specimens this difference is small and is just on the limit of experimental error.Also it is shown that rock-salt and sodium chloride possess identical expansion coefficients within the limits of experimental error.