The dielectric constant of a liquid

Abstract

Some earlier theories in which attempts have been made to allow for the influence of molecular shape on the static dielectric constant of a liquid are shown to be inaccurate. A general equation is derived for the dielectric constant of a liquid, and this is then applied to a molecular model consisting, in the first instance, of an ellipsoid uniformly polarized in a principal direction, and secondly, to an optically anisotropic ellipsoid ; in both cases the surroundings are assumed to form a continuum. The results of this more general approach applied to several substances are more satisfactory than those obtained by the original Onsager theory. The theory is also applied to mixtures, and in the special case of a dilute solution in a non-polar solvent, the equation of Ross and Sack is obtained when the ellipsoid is isotropic. A correlation has been noted in the discrepancies found when the dipole moment of a substance is calculated by means of observations on the pure liquid and on dilute solutions in a non-polar solvent, using the equations derived in the present paper.