Vapour phase composition and activities for the molten PbCl₂ + NaCl system

Abstract

Vapour pressures of molten PbCl₂ + NaCl mixtures have been measured a.t 1071 K by a transpiration method. The vapours have also been investigated by mass spectrometry and the complex NaPbCl₃ has been established. The enthalpy of formation of this complex from NaCl(g) and PbCl₂(g) has been determined and the equilibrium constant for its formation has been estimated. Enthalpies of vaporization of NaCl and PbC1₂ and the enthalpy of dimerization of NaCl(g) agree with published results. The mass spectrometry results have enabled corrections to be made to measured activities of PbCl₂ from the transpiration results, for errors due to the NaPbCl₃ complexes. The activity values so determined are compared with those for other molten binary systems involving lead and alkali chlorides. The PbCl₂ + NaCl system (like the other PbCl₂ + alkali chloride systems except PbCl_{2 +} LiCl) does not behave as regular solutions.