Measurement of Vapor Pressure of Phosphorus over Sn–P Alloys by Dew Point Method

Abstract

The dew points of phosphorus vapor over Sn–P alloys containing 45 mol%P or less have been determined at temperatures ranging from 703 to 973 K. The dew consisting of metastable liquid phosphorus, rather than stable red phosphorus, was utilized. The vapor pressures of P₂ and P₄ were determined from the dew points. Thermodynamic activities and enthalpies of P and Sn were calculated from the vapor pressures. The liquidus line was determined from the temperature and composition dependence of the vapor pressure over coexisting liquid and Sn₄P₃.