Corresponding states for electrolyte solutions*

The equilibrium properties of electrolyte solutions over wide ranges of concentration, temperature, and solvent dielectric constant are discussed on a corresponding-states basis. If low-melting salts are used, these properties can be studied up to the pure fused salt. We mainly focus on systems at low reduced temperature, where the depth of the interaction potential is large compared with the thermal energy. Examples are singly charged ions in solvents of low dielectric constant and of highly charged ions in water. The state of the ions is discussed on the basis of thermodynamic, electrical conductance and dielectric constant data. Special attention is given to the transition to the fused salt, where ion clusters have to redissociate to form the dissociated structure of the salt. This transition can lead to liquid–liquid phase separations. The resulting critical points serve as important targets for testing theories. Examples are given for large deviations from corresponding-states behavior caused by specific short-range interactions.