ABSTRACT
From the definition of the hildebrand parameter, it is apparent that it is necessary to determine both the vaporization energy and the molar volume of a liquid in order to evaluate its Hildebrand parameter. There is rarely much difficulty in finding a reliable value for the molar volume of a liquid, and solids may be treated as subcooled liquids with molar volumes extrapolated to lower temperatures from the liquid state values, but frequently there are problems in obtaining the molar vaporization energy. Several empirical and semiempirical equations have been used for the evaluation of vaporization energies and cohesion parameters of liquids. Cohesive pressure has extremely high values for liquids of high polarity, and very low values for materials such as fluorocarbons where forces of attraction are weak. Liquids of high molecular weight interact in much the same way as polymers with low molecular weight liquids, and their swelling can be used to determine their Hildebrand parameter values.
