Theory of Static Dielectric Behavior of Mixtures of Polar Liquids near a Critical Point

Abstract

The theory of critical fluctuations was employed in an attempt to elucidate the possibly singular behavior of the static dielectric constant which has been observed for mixtures of polar liquids near a critical point. The treatment is similar to existing theoretical treatments of the specific heat singularity. A contribution to the dielectric constant which depends on the correlation length and on the second derivative of the logarithm of the osmotic compressibility with respect to electric field was derived. Some predictions about the existence of and the nature of a singularity in the dielectric constant could be made. These predictions are, however, ambiguous because the precise functional behavior of the osmotic compressibility with electric field in the critical region is still uncertain.