Corresponding States Treatment of Nonelectrolyte Solutions

Abstract

Recent theories of solutions (Prigogine and co-workers; Salsburg and Kirkwood) use a theory of corresponding states to deduce the properties of solutions from theoretically derived properties of the pure components (e.g., from the Lennard-Jones and Devonshire ``free volume'' or ``cell'' model). A characteristic of these theories is that they predict for molecules of the same size and dispersion force interactions a negative volume change on mixing. Since the ``cell'' model gives very poor agreement with experimental data on energy-volume and volume-temperature relations of pure liquids, a corresponding states treatment has been carried through using an experimental equation of state for the pure liquid. If one assumes two kinds of ``cells'' in the mixture, a type for each of the components, the results agree with experimental data on solutions at least as well as previous theories. As before, contraction on mixing is found for a certain class of dispersion force solutions. In any corresponding states treatment, the entropy of mixing will not be ideal either at constant pressure or at constant volume.