Phase diagrams and volumes of mixing in binary systems of molten bismuth(III) chloride with alkali-metal chlorides

Abstract

Phase diagrams representing crystallisation of molten mixtures of bismuth(III) chloride with chlorides of lithium, sodium, potassium, rubidium, and cæsium are presented. No compound formation occurs with lithium chloride, and the latent heat of fusion of bismuth(III) chloride determined cryoscopically (5·7 kcal./mole) agrees with the value determined calorimetrically. With sodium, potassium, and rubidium chlorides, an increasing tendency to form solid complexes is correlated with the decreasing polarising power of the cation. Melts containing cæsium chloride do not follow this trend; weak compound formation occurs over a narrow composition range only, and supercooling (which is pronounced with potassium and rubidium chloride melts) is negligible.

Density values are recorded for melts of bismuth(III) chloride with lithium, sodium, and potassium chlorides at 280, 340, and 400°, over the composition ranges available at these temperatures. In all cases, volumes of mixing are negative and increase with temperature, and give no direct evidence for compound formation in the molten state.