Measurements of saturation densities in critical region and critical loci for binary R-32/125 and R-125/143a systems

R-32/125 (difluoromethane/pentafluoroethane) and R-125/143a (pentafluoroethane/1,1,1-trifluoroethane) binary systems are promising alternative refrigerants to replace conventional refrigerants, i.e., R-22 and R-502. The saturated vapor- and liquid-density data in the critical region of these mixtures were measured using the visual observation of the meniscus disappearance in an optical cell. For the R-32/125 system, 35 saturation density data were measured at three compositions, 10, 35, and 50 mass% R-32. Nineteen saturation density data were also measured for R-125/143a (50/50 mass%). The critical temperatures and densities for these binary refrigerants were determined by taking into consideration the level and location of the meniscus disappearance as well as the intensity of the critical opalescence. Correlations to represent the critical loci of these binary refrigerants for an entire range of compositions have been developed. The experimental uncertainties of the saturation density data are estimated to be within 9 mK in temperature and 0.5 to 5.0 kg · m^-3 in density. The uncertainties of the critical temperature and density are estimated to be within 12 to 14 mK and 4 to 8 kg · m^-3, respectively.