Dielectric constant and dipole moments of 1,1,1-trifluoro-2,2-dichloroethane (HCFC 123) and 1,1-difluoroethane (HFC 152a) in the liquid phase

Experimental data of the dielectric constant of HCFC 123 and HFC 152a as a function of pressure and temperature in the temperature range from 200 to 300 K and pressures up to 18 MPa were correlated as a function of pressure and temperature, with an uncertainty of +/-0.01 for HCFC 123 and +/-0.12 for the HFC 152a, and as a function of density and temperature with an uncertainty of +/- 0.005 for HCFC 123 and +/-0.034 for HFC 152a. The uncertainty of the results obtained for the dielectric constant was estimated at a 95% confidence level to be +/-7.27 x 10(-3) for HCFC 123 and +/-3.26 x 10(-2) for HFC 152a. The theory developed by Vedam and Chen [K. Vedam, C, Chen, Importance of using eulerian representation of strain in high pressure studies on liquids, J. Chem. Phys., Vol. 77, 1982, pp. 1461-1463] and adapted by Diguet [R. Diguet, Density dependence of refractive index and static dielectric constant, Physica, 139 and 140B, 1986, pp. 126-130] and the Kirkwood modification of the Onsager equation for the variation of the modified molar polarization with temperature and density were applied to analyse the data and to obtain the dipole moment of both refrigerants in the liquid state. These were found to be 2.13 D for HCFC 123 and 3.69 D for HFC 152a. (C) 1998 Elsevier Science B.V. All rights reserved.