Activity coefficients in binary liquid mixtures of 3-methyl butene-1 and sulphur dioxide

Abstract

The total vapour pressures above binary liquid mixtures of 3-methyl butene-1 and sulphur dioxide have been measured at intervals of about 4°C in the range 14–40°C. Activity coefficients have been derived at 16, 28 and 40°C by a Gibbs-Duhem mathematical analysis, including corrections for non-ideal vapour behaviour, of total vapour pressure against composition isotherms. Vapour phase compositions have also been calculated. The system shows positive deviations from Raoult's law with an azeotropic mole fraction of 3-methyl butene-1 of 0.15 at 16°C and 0.12 at 40°C. The excess free energy of mixing and the heat of mixing are slightly asymmetric functions of composition; at 28°C the maxima are 197 and 568 cal mole^–1 respectively.