Vapor-liquid coexistence curves in the critical region and the critical temperatures and densities of 1,1,1,2-tetrafluoroethane (R-134a), 1,1,1-trifluoroethane (R-143a), and 1,1,1,2,3,3-hexafluoropropane (R-236ea)

The vapor-liquid coexistence curves in the critical region of 1,1,1,2-tetrafluoroethane (R-134a), 1,1,1-trifluoroethane (R-143a), and 1,1,1,2,3,3-hexafluoropropane (R-236ea) were measured by a visual observation of the meniscus disappearance in an optical cell. Seventeen saturated-vapor and -liquid densities have been measured for R-134a. Thirty-five saturated-vapor and -liquid densities have been measured for R-143a. Twenty-seven saturated-vapor and -liquid densities have been measured for R-236ea. The level and location of the meniscus, as well as the intensity of the critical opalescence were considered in the determination of the critical temperature and density for each fluid. R-134a was found to have (374.083 +/- 0.010) K and (509 +/- 1) kg/m(3), R-143a, (345.860 +/- 0.010)K and (434 +/- 1) kg/m(3), and R-236ea, (412.375 +/- 0.015) K and (568 +/- 1) kg/m(3).