A Simplified Model for Calculation of the Gibbs Energy of Mixing in Crystals: Thermodynamic Theory, Restrictions and Applicability

Abstract

A simplified model has been set up for calculation of the molar Gibbs energy of mixing ∆mixGm(s) in crystals based on the assumption of a complete liquid-solid thermodynamic equilibrium in the water-salt systems. The procedure allows the ∆mixGm(s) values to be calculated from the experimental solubility data for the saturated binary and ternary solutions. The ∆mixGm(s) values and the excess Gibbs energy of mixing ∆mixGEm(s) were calculated for six alkali-halide systems (KCl-RbCl-H2O, KBr-RbBr-H2O, KI-RbI-H2O, NH4Cl-NH4Br-H2O, RbCl-RbBr-H2O and CsCl-CsBr-H2O). The results obtained were compared with experimental data taken from the literature and values calculated based on various theoretical approaches.