Extension of a two-structure model for electrolyte solutions to aqueous mixed electrolyte systems☆

Abstract A two-structure model for electrolyte solutions has been extended to the prediction of the activity coefficient of each component in a mixed electrolyte solution. Activity coefficients predicted using this model agree as well with fitted-observed values for a number of mixtures as those predicted using a model which retains a Debye-Huckel term at all ionic strengths. The advantages of the two-structure model include: (1) fewer adjustable parameters are needed per component electrolyte; and (2) the fact that two of the parameters describing the ionic strength dependence of the activity coefficient of the component electrolytes seem to have direct physical origin.