Correlation of mean ionic activity coefficients of electrolyte solutions by the simplified nonprimitive mean spherical approximation

The mean ionic activity coefficients of 38 single 1:1 electrolytes are correlated by a simplified nonprimitive model of mean spherical approximation (σ+=σ-≠σn) combined with statistical associating fluid theory, in which only the diameter of ions (σi) is treated as adjustable parameter. The ion–ion, ion–dipole and dipole–dipole interactions are represented by three implicit parameters, b0, b1 and b2, respectively. The statistical associating fluid theory is adopted to deal with the association interaction for water molecules. The correlated accuracy with this simplified equation is acceptable. Some advantages and disadvantages of the model are discussed.