Thermodynamics of electrolytes. 13. Ionic strength dependence of higher-order terms; Equations for CaCl2 and MgCl2

While the original ion-interaction (Pitzer) equations of 1973 were adequate for many electrolytes to the limit of solubility, additional terms are nee ded for some systems of large solubility. A simple pattern of ionic-strengt h dependence is proposed for third, fourth, and higher virial coefficients. It is found to be very effective in representing the complex behavior of C aCl2(aq) as well as that of MgCl2(aq) at 25 degrees C. Equations without io n association are presented for each system that are valid for the full ran ge to 11.0 and 5.9 mol-kg(-1), respectively, as well as simpler equations f or limited molality ranges.