Permittivity of Polar Solutions in Non-Polar Solvents

By an extension of the theory of dielectric permittivity as previously developed by the author for pure liquids, the case of the solution of a polar compound in a non-polar solvent is investigated. The substitutional model first introduced by Faber and Ziman for liquid metal alloys is shown to provide an excellent framework for the present problem, since liquid dilatation around a solute molecule has a negligible influence on the expression of the local field. The resulting formula for the dielectric permittivity is found to be in better agreement with experiment than the corresponding equation deduced from Onsager's theory.