Gas-Phase PVT Properties and Vapor Pressures of Pentafluoroethane (HFC-125) Determined According to the Burnett Method

The gaseous compressibility factors of pentafluoroethane (HFC-125) have been measured by a Burnett apparatus in the range of temperatures from 290 to 390 K and pressures up to 3.6 MPa. The vapor pressures in the range of temperatures from 290 K to the critical temperature have also been measured, and a vapor-pressure correlation has been developed. The critical pressure was determined to be 3.6199 ± 0.0018 MPa on the basis of the present measurements. The second virial coefficients have been determined along 11 isotherms, and a truncated virial equation of state has also been developed to represent the temperature dependence of the second virial coefficients and the present Burnett measurements. The experimental uncertainties of temperature, pressure, and density measurements throughout the present study were estimated to be better than ±10 mK, ±0.8 kPa, and ±0.12%, respectively. The purity of the HFC-125 sample used was better than 99.998 mass %.