MODELING OF THE TEMPERATURE DEPENDENCE OF THE EXCESS PROPERTIES OF MIXING OF FELDSPARS

Abstract

Experimental data on phase equilibria were matched with calorimetric and crystallographic data on K-Ca-Na feldspars by thermodynamic modeling of a ternary feldspar solid solution. The excess functions of mixing were described by original thermodynamic models based on the temperature-dependent terms of the excess heat capacity. The proposed models were compared with the model based on the generally accepted Margules entropy and enthalpy series, which gives a linear approximation of the temperature dependence of the free energy of mixing. It was shown that the proposed thermodynamic models are not worse than the linear approximation of the free energy of mixing and have some positive features.