Entropy of Vaporization and Restricted Molecular Rotation in Liquids

Deviations among entropies of vaporization to constant vapor volume are attributed to restricted rotation of molecules in the liquid. An arbitrary measure of the amount of restriction is defined and the deviations are shown to exhibit a remarkable regularity when compared on this basis. Deviations due to perturbation of vibrations in the liquid must either parallel those due to restricted rotation or be quite small.