Solubilities of Copper and Sulfur in Molten Lead

Abstract

Equilibrium experiments were performed between molten lead and PbS-Cu₂S mixed sulfide. The PbS-Cu₂S system has an eutectic type phase diagram. Experimental temperatures were higher than the eutectic temperature in the range of 823 K to 1073 K. The compositions of PbS-Cu₂S corresponded to the two phases of liquid mixed sulfide and solid PbS or liquid mixed sulfide and solid Cu₂S at the experimental temperature. After cooling, a lead sample was analyzed for copper and sulfur.
A good linear relationship between logarithms of copper concentration and reciprocal values of the absolute temperatures was obtained. In the case of sulfur, the similar tendency was obtained.
The experimental values were compared with evaluated values calculated using the solubility of sulfur in the Pb-S binary system and the interaction parameter between copper and sulfur in liquid lead from the literature.
The standard Gibbs energy of the following reaction, 2Cu(% in Pb) + S(% in Pb) = Cu₂S(s), was evaluated by using the experiment results.