Thermodynamic studies of triangular molecules: Liquid mixtures of xenon and the boron halides, BF3 and BCl3

The total vapour pressure of the liquid mixtures Xe-BF3 and Xe-BCl3 has been measured at 182.33 K (the triple point of nitrous oxide). Both systems show positive deviations from Raoult's law and in the case of Xe-BF3, the system exhibits liquid-liquid immiscibility and an heteroazeotrope. The excess molar Gibbs energy (G(m)(E)) has been calculated from the vapour pressures. The molar volumes of Xe-BCl3 have also been measured at the same temperature and the corresponding excess molar volumes (V-m(E)) calculated. The results were interpreted using Deiters' equation of state.