Abstract: More accurately calculating the heat of formation and standard entropy of phosphate, andappliying thermodynanric first approximate equation, the authors analysed the melting proeessof phosphate glass. Oxygen and water existing in the system are the mAlN reason of Pt cruciblebeing eroded, and the erosive products Pt(PO₃)₂ and Pt(PO₃)₄ can easily react with free oxides,releasing Pt particles. POCl₃ atmosphere introduced can either eliminate water and free oxides,or insulate air, so that Pt particles can be decreased.

Key words: estimation of heat of formation, estimation of standard entropyt phosphate glass, erosion of platinum