THE CHARGE-DIPOLE CONTRIBUTION TO THE DENSITY-DENSITY CORRELATION MATRIX IN NEAR-CRITICAL ELECTROLYTES

A charge-dipole term in the ion-solvent contribution to the density-de nsity correlation matrix of an ionic solution is identified, and its e ffect on the thermodynamics of the solution near its critical point is investigated. It is pointed out that such a term will appear in the d escription of an ionic melt in the absence of a molecular solvent if t he melt is regarded as a mixture of free ions in a solvent of ions tha t have ionically associated to some extent into dipolar pairs. It is c oncluded that the presence of such a charge-dipole term might signific antly perturb the Ising-like thermodynamic behavior that one expects i n a pure dipolar solvent in its critical region, but in a way that is too system-dependent to permit universal statements to be made about i ts quantitative effect.