AN EMPIRICAL MIXING RULE FOR ESTIMATING MEAN IONIC ACTIVITY-COEFFICIENTS IN MULTIELECTROLYTE SOLUTIONS FROM BINARY DATA ONLY

An empirical mixing rule is proposed for mean ionic activity coefficient of electrolytes in multielectrolyte mixtures. The mean activity coefficients are calculated from data of the constituent binary single-salt water solutions only. Using the mixing rule, the trace mean activity coefficients and the Harned's coefficients of electrolytes in ternary mixtures with and without a common ion are predicted and compared with literature data. The agreement of the calculated values with the experimental data is very good, particularly for systems which follow Bronsted ion interaction theory. Calculations for sea water are presented as example for multielectrolyte systems. The predictions agree well with experimental data.