ALTERNATIVE REFRIGERANTS CH2F2 AND C2HF5 - CRITICAL-TEMPERATURE, REFRACTIVE-INDEX, SURFACE-TENSION, AND ESTIMATES OF LIQUID, VAPOR, AND CRITICAL DENSITIES

Refractive index data and capillary rise data are reported for CH2F2 and C2HF5, which are denoted as R32 and R125 by the refrigeration industry. For each fluid, the data extend from 296 K to the critical point and yield the critical temperature T,and the temperature-dependent capillary length. the refractive index data were combined with liquid density data at 303 K to determine the Lorentz-Lorenz constant it. This constant and the data were used to estimate the liquid,vapor, and critical densities, and the surface tension a up to the critical point. For both fluids, the surface tension a is given by the expression sigma = S(o)t(126)k(B)T(c)(N-A/V-c)(2/3) with S-o = 5.5 for R32 and S-o = 6.0 for R125. Here k(B), N-A, T-c, and V(c)are the Boltzmann constant, the Avogadro constant, the critical temperature, and the molar critical volume, respectively, and t = (T-c - T)/T-c. The present values for S-o are close to the average value S-o = 5.7 for seven other refrigerants.