Freezing Points of Electrolyte Mixtures. I. Mixtures of Sodium Chloride and Magnesium Chloride in Water

The freezing points of aqueous mixtures of sodium chloride and magnesium chloride have been measured in the range of ionic strengths from 0.1 to 3.5 mole-kg(-1). The composition dependence of the excess Gibbs function is considered from the standpoint of the Scatchard ion-component treatment of electrolyte solutions. The ion-component equations predict the osmotic coefficients of the mixtures from the single-salt results with a maximum error of less than 1%. Values of Friedman's parameter w(o) at the freezing points of the solutions are compared with isopiestic and theoretical values at 298 K.