Solubility of tin and germanium in liquid sodium: the sodium–tin partial phase diagram

Abstract

The solubility of tin (up to 6·9 atom %) and of germanium (up to 1·0 atom %) in liquid sodium has been determined by thermal analysis and electrical-resistance methods. The compound NaGe precipitates from dilute solutions of germanium in sodium. Partial molar Enthalpies and entropies of solution in sodium for tin (with respect to Na₁₅Sn₄) and germanium (with respect to NaGe) are 46·8 and 44·3 kJ mol^–1 and 50·7 and 29·7 J K^–1 mol^–1 respectively. A simple thermochemical cycle is used to demonstrate that metallic tin and lead dissolve exothermically in liquid sodium but that carbon dissolves endothermically; the cycle is also used to derive solvation energies for the elements Pb, Sn, and C which increase in the order Pb < Sn < C. The sodium–tin phase diagram is augmented over the range 0–6·9 atom % Sn.