Phase diagram measurements and thermodynamic analysis of the PbCl2–NaCl, PbCl2–KCl, and PbCl2–KCl–NaCl systems

Abstract

The phase diagrams of the PbCl2–NaCl and PbCl2–KCl systems have been measured by the cooling curve technique. In addition, a number of measurements at compositions in the ternary system PbCl2–KCl–NaCl have been made. The binary data have been analysed along with other available thermodynamic data for the binary systems in order to obtain mathematical expressions for the binary thermodynamic properties. Various estimation procedures were then used to calculate the Gibbs energy of the ternary liquid from the binary expressions, and the ternary phase diagram calculated therefrom was compared to the experimental ternary points. In the case of the Conformal Ionic Solution equation, agreement was within 3 °C at all measured points. In the case of two "geometric" estimation techniques, the Kohler and Toop equations, agreement was within 10 °C but could be brought to within 3 °C by the addition of only one small adjustable ternary correction term. The technique of coupled thermodynamic/phase diagram analysis permits a large reduction in the amount of experimental work necessary to measure the ternary diagram. In addition, the ternary thermodynamic expressions developed can be used to calculate all thermodynamic properties of the ternary liquid.