Thermodynamics on the Vapor Formation of Lead Oxychloride

The vapor pressure of PbCl 2 at high oxygen partial pressure was measured by transpiration method at 923K, 973K and 1023K. The vapor pressure of PbCl 2 decreases with increasing the oxygen partial pressure. The oxygen content in PbCl 2 melt and the chlorine partial pressure in the system increase with increasing the oxygen partial pressure. These results indicate that the activities of PbCl 2 are changed by the formation of lead oxychloride in the melt at high oxygen partial pressure. The formation reaction of lead oxychloride in the melt is suggested by the reaction PbCl 2 (l) + 1/2O 2 (g) = PbOCI (l) + 1/2Cl 2 (g). Based on the oxygen contents in the PbCl 2 melt and the vapor pressure of PbCl 2 , the activities of PbCl 2 and PbO in the PbCl 2 -PbO system are calculated. The calculated activities show a negative deviation from Raoult's law.