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 PbCl2 + LiCl) does not behave as regular solutions.