Vapor pressures of 1,1,1,2,3,3,3-heptafluoropropane, 1,1,1,3,3,3-hexafluoropropane and 1,1,1,3,3-pentafluoropropane

The vapor pressures of three important fluorinated propanes, 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea), 1,1,1,3,3,3-hexafluoropropane (HFC-236fa) and 1,1,1,3,3-pentafluoropropane (HFC-245fa) were measured precisely with an improved experimental system in the temperature range of 234–371, 239–398 and 235–427 K, respectively. The uncertainty of the vapor pressures was estimated to be ±300 Pa. The experimental samples were prepared carefully and analyzed with a gas chromatographic (GC) system and a gas chromatographic coupled with a mass spectrum (GC/MS) system. The effects of impurities on the vapor pressure were also considered to explain the discrepancies between the experimental results and other literature data. Wagner-type vapor pressure equations were correlated from the experimental results for the three fluids. The critical pressure, normal boiling point, triple-point pressure and acentric factor for the three substances were also obtained from the vapor pressure equations.