HIGH-TEMPERATURE PHASE-RELATIONS AND THERMODYNAMICS IN THE IRON-LEAD-SULFUR SYSTEM

The PbS activities in FeS-PbS liquid mattes were obtained at 1100-degr ees-C and 1200-degrees-C by the dew-point method. Negative deviations were observed, and the liquid-matte solutions were modeled by the Krup kowski formalism. The liquid boundaries of the FeS-PbS phase diagram w ere derived from the model equations yielding a eutectic temperature o f 842-degrees-C at X(Pbs) = 0.46. A phase diagram of the pseudobinary FeS-PbS was also verified experimentally by quenching samples equilibr ated in evacuated and sealed silica capsules. No terminal solid soluti on ranges could be found. Within the Fe-Pb-S ternary system, the bound aries of the immiscibility region together with the tie-line distribut ions were established at 1200-degrees-C. Activities of Pb were measure d by the dew-point technique along the metal-rich boundary of the misc ibility gap. Activities of Fe, Pb, and S, along the miscibility gap we re also calculated by utilizing the bounding binary thermodynamics, ph ase equilibria, and tie-lines.