Mass Spectrometric Determination of Activities of P<SUB>2</SUB>O<SUB>5</SUB> in PbO-P<SUB>2</SUB>O<SUB>5</SUB> and Fe<SUB>t</SUB>O-P<SUB>2</SUB>O<SUB>5</SUB> Systems

Abstract

The activities of P2O5 in the PbO-P2O5 system at 1 300°C and in the FetO-P2O5 system at 1 370°C-1 390°C have been determined by the use of the combination of a mass spectrometer and a KNUDSEN-cell using the relation (P2O5) +PO(g) =3PO2(g).The obtained resultes are as follows.The PbO-P2O5 system:The GIBBS-DUHEM relationship has been found to exist between the activity of P2O5 obtained from the ion currents of PO+ and PO+2 and that of PbO obtained from the ion currents of PbO+. The existence of such relationship confirms the validity of mass spectrometric determination of the activity of P2O5 in slags from the ion currents of PO+ and PO+2.The FetO-P2O5 system:This system has been found to obey HENRY'S law up to 0.08 mole fraction of P2O5.The following activity coefficients of P2O5 were obtained at 1 370°C-1 390°C from the ion currents of PO+ and PO+2.γP2O5= (2.2±0.8) × 10-15 at 1 370°C=(2.5±0.8) × 1015 at 1 380°C=(2.8±1 ) × 10-15 at 1 390°C 0