MEASUREMENT OF THE DIPOLE-MOMENT OF GASEOUS 1,1,1-TRICHLOROTRIFLUOROETHANE, 1,2-DIFLUOROETHANE, 1,1,2-TRICHLOROTRIFLUOROETHANE, AND 2-(DIFLUOROMETHOXY)-1,1,1-TRIFLUOROETHANE

The relative permittivity (dielectric constant) in gaseous 1,1,1-trichlorotrifluoroethane, 1,2-difluoroethane, 1,1,2-trichlorotrifluoroethane, and 2-(difluoromethoxy)-1,1,1-trifluoroethane at temperatures between 293 and 378 K has been obtained from capacitance measurements using a parallel plate capacitor. Molecular polarizabilities have been determined from the results. We report the electronic polarization for each fluid determined from liquid-phase index of refraction measurements at 297 K. Equilibrium dipole moments (mu) have been determined from the combined results. Estimates are given for the dipole moment of individual conformers where the dipole moment is temperature dependent. 1,2-Difluoroethane, for which d-mu/dT < 0, exhibits the gauche effect; the temperature dependence of mu for 1,1,2-trichlorotrifluoroethane is similar. We also report liquid densities for 1,1,1-trichlorotrifluoroethane and 1,2-difluoroethane.