CRITICAL PARAMETERS FOR HFC134A, HFC32 AND HFC125

The vapour-liquid coexistence curves near the critical point for HFC134a (CF3CH2F: 1,1,1,2-tetrafluoroethane), HFC32 (CH2F2: difluoromethane) and HFC125 (CHF2CF3: pentafluoroethane) have been measured by visual observation of the meniscus disappearance. Three sets of 17 experimental results for the saturated liquid or vapour densities for HFC134a, HFC32 and HFC125 have been obtained in the reduced temperature range T/T(c) > 0.96 and in the reduced density range 0.4 < rho/rho(c) < 1.7. From these measurements, the critical temperature and the critical density for these HFCs have been determined in consideration of the meniscus disappearance level as well as the intensity of the critical opalescence. The critical pressure has been calculated by the extrapolation of the vapour-pressure correlation. The uncertainties of the critical temperature, critical density and critical pressure are estimated to be within +/- 10 mK, +/- 5 kg m-3 and +/- 9 kPa, respectively.