New modified Wilson model for electrolyte solutions

A new model is proposed to model the activity coefficients of electrolytes in aqueous solutions. The model consists of two contributions: one due to long-range forces represented by the unsymmetric Pitzer-Debye-Huckel equation and the other due to short-range forces described by a new local composition expression. This last term is obtained from work presented in a previous paper for polymer aqueous solutions. With only two adjustable parameters per electrolyte, the new expression for the short-range excess Gibbs energy has the same form as the Wilson model for nonelectrolytes. The new equation is tested with experimental data available in the literature. The mean ionic activity coefficients of electrolytes are represented very satisfactorily. The performance of the new equation is compared with the performances of the other three models.