Calculation of Thermodynamic Properties of Fused Salts from a Rigid-Sphere Equation of State

Abstract

A rigid-sphere equation of state developed by Reiss, Frisch, and Lebowitz was used as a starting point for the development of expressions for the absolute entropy, entropy of fusion, heat capacity, and compressibilities of molten alkali halides. The absolute entropy of 2 moles of rigid spheres, compressed to the volume of the fused salt, was found to be equal to that of the molten salt. The entropy of compressing these rigid spheres from the molar volume of the liquid to the volume of the solid was in good agreement with the entropy of fusion of fused alkali halides. The heat capacity calculated by the differentiation of the expression for the absolute entropy, at constant pressure of the liquid, was also in good agreement with experimental values. However, the agreement between the calculated compressibility and the experimental results was not good.