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 a nd C2HF5, which are denoted as R32 and R125 by the refrigeration indus try. For each fluid, the data extend from 296 K to the critical point and yield the critical temperature T,and the temperature-dependent cap illary length. the refractive index data were combined with liquid den sity data at 303 K to determine the Lorentz-Lorenz constant it. This c onstant and the data were used to estimate the liquid,vapor, and criti cal 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, th e 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 refrigerant s.