Determination of the Pitzer Interaction Parameters at 273.15 K from the Freezing-Point Data Available for NaCl and KCl Solutions

Abstract

A novel calculation method is presented in this work to evaluate the ion interaction parameters for the Pitzer model from freezing points of aqueous solutions of pure electrolytes. The freezing-point depression data from aqueous solutions of sodium chloride and potassium chloride are used to epitomize this method. The parameter values obtained using this method predict more accurately the experimental data than the most often used values for the Pitzer method up to a molality of 1.5 mol·kg–1. The parameters obtained by the freezing-point technique are associated with the solutions which are below the temperature of 273.15 K. It is verified in the present study that the temperature dependences of these parameters between the two temperatures are, however, practically negligible at molalities less than 0.5 mol·kg–1. In addition to the freezing-point data existing in the literature, the validity of the parameters was also studied using the literature results from concentration cells without transference.