Solution properties of water in molten AgNO3–LiNO3 mixtures as derived from vapour-pressure measurements on AgNO3–LiNO3–H2O melts

Abstract

The results of extensive vapour-pressure measurements on highly concentrated aqueous solutions of AgNO₃, LiNO₃ and their binary mixtures in the temperature range 320 < T/K < 380 are treated by means of the Stokes–Robinson adsorption–hydration theory. The structural and energetic parameters in the theoretical equation are calculated after completing the set of measurable data for AgNO₃–H₂O melts with extrapolated data from the literature. Examination of the dependence of the adsorption–hydration energy on the composition of the nitrate mixture in the light of a previous theory for selective ionic hydration in such melts reveals the existence of an additional contribution to the predicted hydration energy of the AgNO₃–LiNO₃ melts. This excess hydration energy term is discussed in relation to the known positive excess free energy of mixing of anhydrous AgNO₃–LiNO₃ molten mixtures. In this way the dissolved water acts as a probe of the mixing features of the molten salts.