Thermodynamics of Electrolyte Solutions

Abstract

Progress in the thermodynamics of ionic solutions is reviewed with emphasis on practical application. Systems of thermodynamic quantities for solutions containing ionic species are outlined. The method of statistical thermodynamics is described. Models of electrolyte solutions at the McMillan-Mayer (MM) level and the methods of computation of thermodynamic properties of ionic solutions within the MM theory including cluster expansions, integral equations, ion association and perturbation theories, are summarized. The ion association theory combined with MSA plus virial coefficients for ion-ion and pair-ion interactions are compared with HNC and Monte Carlo data for a common model of the 2-2 electrolyte. The approach to the investigation of the structure of liquid systems, particularly water and aqueous ionic solutions, at the Born-Oppenheimer (BO) level is mentioned. BO-level molecular models and computational methods are characterized and the application to ionic hydration is noticed. Semi-empirical models for the calculation of thermodynamic properties of electrolyte solutions are summarized. These include combined models (such as DH plus van Laar), perturbation methods, ion association models and two variations on the cluster expansion, namely the Guggenheim equation modified with MSA in place of the DH term, and particularly the Pitzer equation. Computation of thermodynamic quantities in mixed electrolytes is discussed. Calculations and the use of individual ionic quantities are commented.