THERMODYNAMICS OF LIQUID-MIXTURES OF XENON + HEXAFLUOROETHANE

It has recently been reported that liquid xenon and liquid ethane mix with negative values of the three main excess thermodynamic functions, namely the excess Gibbs energy GE, the excess enthalpy HE, and the excess volume VE. One possible reason for this surprising behaviour is unusually favourable quadrupole-induced dipole interaction. It therefore seemed worthwhile to investigate the thermodynamic properties of mixtures of xenon + hexafluoroethane, since the molecules of hexafluoroethane should have a larger quadrupole moment than those of ethane. We have measured GE and VE for this system at 173.11 K, and HE at 175.00 K. All three functions are positive at all compositions and relatively large, the values for x = 0.5 at the stated temperatures being GE = 621 J mol-1, VE = 2.35 cm3 mol-1, and HE = 1079 J mol-1. © 1979.