High-temperature reaction calorimetry has been applied in a thermochemical study of solid and liquid phases in part of the quasi-binary system Cu2S-Sb2S3. The enthalpies of formation at 298 K of the sulfosalts chalcostibite (CuSbS2) and monoclinic skinnerite (Cu3SbS3) from their end-member component sulfides (Cu2S and Sb2S3) were determined to be −20.2 ± 2.1 kJ·mol−1 and −24.8 ± 2.7 kJ·mol−1, respectively.
Mixtures of solid Cu2S and liquid Sb2S3 at 895 K were studied by solid-liquid reaction calorimetry, and by dilution calorimetry, with pure liquid Sb2S3. Measurements of the solid-liquid enthalpies of mixing (in kJ·mol−1) yielded the linear expression
based on experiments with values of XCu2S ranging from 0.1 to 0.4. This equation is consistent with a symmetrical, regular-solution model and implies that the heat of fusion of Cu2S at 895 K (for XCu2S = 1.00) is 9.5 kJ·mol−1. Our data yield an average value for ΔCP,S-L,Cu2S of 6.6 J·K−1 · mol−1.