An analytical method of calculating thermodynamic data in ternary systems

Abstract

Relationships between the coefficients of series expansions in the composition variables for isothermal partial molar properties of all components, and for the corresponding integral property in a ternary system, have been developed. These relationships allow the calculation of the isothermal partial properties of mixing of all components, from experimental values of this property for one component, or from experimental measurements of the corresponding integral property of mixing. The form of the series expansions is such as to permit the easy fitting of the experimental data by standard least-squares techniques. Experimental data in a binary sub-system or experimentally determined phase boundary positions may easily be used to give end-points for the calculation. The method is faster and more accurate than the older graphical integration techniques. The simplicity of the method depends upon the proper choice of composition variables. Sample calculations have been done for the Cd–Bi–Sn system, using computer programs designed for the purpose.