Prediction of water activities in multicomponent solutions of metal chlorides from the thermodynamic properties of corresponding binary systems

In order to calculate the activity coefficients of water in aqueous solution of metal electrolytes, a simplified model predicting them in ternary or multicomponent solutions with common anions from the activity data of water of the corresponding binary systems has been developed based on an assumption that the electrolytes in the solution are treated as independent particles instead of their ion forms, and the interaction of the salt(i)-salt(j) pair in the solution is assumed to be much weaker than that of water-salt pair due to the common anions of both of salts. The model was applied to the systems such as KCl-H2O-NaCl, MCl-H2O-M′ Cl2 (M represents Na and K, M′ represents Ca and Ba) and KCl-H2O-NaCl-BaCl2 with satisfying results. The interchange energies of the studied component pairs between water and salts have also been determined by the corresponding binary aqueous solutions.