Deuterium and hydrogen sulfides: vapor pressures, molar volumes, and thermodynamic properties

Abstract

An apparatus is described in which deuterium and hydrogen sulfides have been prepared by the hydrolysis of aluminum sulfide. Liquid densities have been determined at −79 °C and give the molar volumes 34.811 ± 0.003 cm3 for deuterium sulfide and 34.711 ± 0.003 for hydrogen sulfide. Vapor pressures of deuterium and hydrogen sulfides have been determined at −78 °C in a quartz–metal apparatus, and in the range −30 to +30 °C in a stainless steel apparatus. Equations are derived for the deuterium and hydrogen sulfide vapor pressures and for their ratio. An isotopic vapor pressure cross-over point is found at −48 °C, above which deuterium sulfide is more volatile than hydrogen sulfide. Gas and liquid molar volumes and enthalpy changes are evaluated for liquid vaporization at saturation. The deuterium and hydrogen sulfide vaporization standard thermodynamic function changes and their errors, together with the isotopic differences for these functions and their errors, are tabulated between −80 and +50°C.