Corresponding states for ionic fluids

Abstract

Corresponding states ideas are applied to correlate a number of equilibrium properties of ionic fluids. Consideration is given to the thermodynamic excess functions used to characterize dilute ionic fluids, to ion pairing and higher association, and to the characteristic coexistence curve and critical point found in many ionic fluids. The correlation applies to simple ionic fluids such as liquid or gaseous salts, to plasmas, and to ionic solutions as well as to the primitive model to the degree that the properties of all these systems are known. New HNC calculations are reported that were made to elucidate the structural changes in an ionic system as it is compressed along an isotherm corresponding to 2–2 aqueous electrolytes. Finally an evaluation is given of the usefulness of a number of approximation methods for calculating the equilibrium properties of the primitive model, and presumeably other Hamiltonian models, in various regions of the corresponding states diagram. Among these methods is the theory of Bjerrum (1926) which is surprisingly accurate, although some of its limitations are illustrated in the present work.