Ternary Excess Enthalpies in Reciprocal Fused Salt Mixtures. IV. Effect of Charge Asymmetry

Calorimetric measurements have been carried out on the enthalpies of mixing in the reciprocal systems Cd2+–Ag+–Cl−–NO3− and Cd2+–Tl+–Cl−–NO3−. The results, when compared with corresponding data for the binaries and for the metathetical reactions, enable us to evaluate the ternary excess enthalpies. In order to give the results in a simple algebraic form we have adopted the concept of the equivalent enthalpy of mixing, and have expressed compositions in terms of equivalent ionic fractions. It is found that the ternary excess enthalpies for the system Cd2+–Ag+–NO3−–Cl− may be accounted for by a suitable adaptation of the quasichemical theory. This suggests that these excess enthalpies largely are due to deviations from random mixing in the relative arrangement of cations and anions. However, for the system Cd2+–Tl+–NO3−–Cl− the ternary excess enthalpies show orders-of-magnitude deviations from the predictions of our adaptation of the quasichemical theory.