Thermodynamic properties of clathrates: I. The heat capacity and entropy of argon in the argon quinol clathrates

Measurements have been made of the heat capacity C_p from ～ 13°k to ～ 273°k of five clathrates of argon and β-quinol. The argon content ranged from ～ 20 per cent to ～ 80 per cent of the maximum possible amount. Over much of the temperature range studied, C_p proved to be a linear function of the argon content, but from 13°k to 20°k, and from 50°k to 100°k the relation between C_p and argon content is obscure, and may, in fact, be non-linear. Estimates have been made of the contribution to C_p made by a mole of argon in the temperature region where C_p is a linear function of composition, and these experimental values have been compared with those calculated according to the theory of J. H. van der Waals, which is based on the cell model of Lennard-Jones and Devonshire. The agreement between theory and experiment is satisfactory.