Vapour pressures, liquid densities, and vapour densities were measured for pentafluoroethane (R125) and 1,1-dichloro-1-fluoroethane (R141b) at temperatures between -135 deg F (180 K) and 400 deg F (480 K) and pressures to 10,000 psia (70 MPa). The critical temperatures were measured and critical pressures derived for each fluid. The experimental values were used to develop correlations for the measured properties. Enthalpies and entropies for the saturated liquid, saturated and superheated vapour, and the heat capacities of saturated liquid and vapour were derived for R125 from the PVT behaviour and ideal gas heat capacities. The correlations provide vapour densities accurate to better than plus or minus 0.05%, liquid densities accurate to better than plus or minus 0.1%, vapour pressures accurate to plus or minus 0.05%, calculated enthalpies and entropies accurate to plus or minus 1%, and heat capacities accurate to plus or minus 5%.

KEYWORDS: Thermodynamics, refrigerants, R125, R141b, vapour pressure, measuring, entropy, heat content, gases, vapours, accuracy, experiment.