Abstract
The phase diagrams of the systems Bi 2 S 3 -BiX 3 were constructed from results of DTA and total pressure measurements and x-ray analysis. The phases: BiSCl, Bi 4 S 5 Cl 2 and Bi 19 S 27 Cl 3 for X = Cl; BiSBr and Bi 19 S 27 Br 3 for X = Br; BiSI and Bi 19 S 27 I 3 for X = I exist on the boundary lines. The enthalpies of formation and standard entropies of the phases follow from the coexistence decomposition pressure functions. The data are: ΔH°B(BiSCl f,298 ) =−49,6 ± 1,6 kcal/mol S°(BiSCl f,298 ) = 30,3 ± 2,5 cal/K·mol ΔH°B(Bi 4 S 5 Cl 2,f,298 ) =−144,4 ± 3 kcal/mol S°(Bi 4 S 5 Cl 2,f,298 ) = 114,0 ± 4,6 cal/K·mol ΔH°B(Bi 19 S 27 Cl 3,f,298 ) = −520 ± 10 kcal/mol S°(Bi 19 S 27 Cl 3,f,298 ) = 490 ± 10 cal/K·mol ΔH°B(BiSBr f,298 ) = −40,2 ± 1,4 kcal/mol S°(BiSBr f,298 ) = 32,0 ± 3 cal/K·mol ΔH°B(Bi 19 S 27 Br 3,f,298 ) = −493,6 ± 6,7 kcal/mol S°(Bi 19 S 27 Br 3,f,298 ) = 499,8 ± 17 cal/K·mol ΔH°B(BiSI f,298 ) =−27,8 ± 1,4 kcal/mol S°(BiSI f,298 ) = 36,1 ± 2,5 cal/K·mol ΔH°B(Bi19S27I3,f,298) =−464,4 ± 15 kcal/mol S°(Bi 19 S 27 I 3,f,298 ) = 502,7 ± 15 cal/K·mol