Statistical Mechanical Derivation of Onsager's Equation for Dielectric Polarization

The assumptions necessary in deriving the equation for the dielectric polarization in the absence of short‐range interactions between the molecules, as represented by the Onsager equation, are made explicit. The equation derived by Harris and Alder for the general case of dielectric polarization of polar liquids is seen to involve an approximation not previously stated. The latter equation, when reduced to the limit represented by the Onsager equation, becomes identical to it when a further simplification is introduced.