Solubilities of nickel and phosphorus in molten lead

Abstract

Equilibrium experiments were performed between molten lead and six combinations of two adjacent nickel phosphides (Ni–Ni₃P, Ni₃P–Ni₅P₂, Ni₅P₂–Ni₁₂P₅, Ni₁₂P₅–Ni₂P, Ni₂P–Ni₅P₄ and Ni₅P₄–NiP₂) at 973, 1023, 1073 and 1123 K. After cooling, a lead sample was analysed for nickel and phosphorus. Both nickel and phosphorus contents increased with increasing temperature. Nickel concentration decreased and that of phosphorus increased with increasing phosphorus to nickel ratio in each combination of two phases. The standard Gibbs energies of the following three reactions, Ni₅P₂+Ni=2Ni₃P, 2Ni₁₂P₅+Ni=5Ni₅P₂ and 5/2Ni₂P+Ni=1/2Ni₁₂P₅, were evaluated and thermodynamically discussed using nickel activity obtained in this study.