The Standard Free Energies of Dissolution of Phosphorus Gases in Liquid Iron

Abstract

The vapor pressures of phosphorus gases, P and P₂, above Fe-P alloys have been determined by a newly developed experimental method. In this experimental method, phosphorus in the deposit film obtained by the Knudsen effusion method with collection technique was determined by a secondary ion mass spectrometer. The vapor pressures of P and P₂ have been obtained from these determined values and the ratio of the ion currents of P⁺ to those of P⁺₂ which had been obtained by the ordinary Knudsen cell-mass spectrometer combination. The standard free energy changes of the reactions for liquid Fe-P alloy system were calculated from these vapor pressures, and the following values have been obtained.
P(g)=P(wt%)
ΔG°=-95.3+1.55×10^-2T(±2.2)(kcal/mol)
1/2P₂(g)=P(wt%)
ΔG°=-37.7+0.13×10^-2T(±1.1)(kcal/mol)
P(g)=1/2P₂(g)
ΔG°=-57.6+1.42×10^-2T(±1.1)(kcal/mol)
(1-3wt% P, 1590-1650°C)