Physical PropertiesChemical Name Difluoromethane PentafluoroethaneChemical Notation Ch2f2/ Cf3chf2Molecular Weight 72.6Boiling Point @ 1 Atm, ( ° F) -60.6Freezing Point @ 1 Atm, ( ° F) -247Critical Temperature ( ° F) ( Astm D-1321) 160.44Critical Pressure* ( Psia) 711.07Saturated Liquid Density @ 86° F, ( Lb/ Ft3) 64.5Specific Heat Of Liquid @ 86° F, ( Btu/ Lb• ° F) 0.42Specific Heat Of Vapor @ Constant Pressure* ( Cp) , @ 86° And 1 Atm, ( Btu/ Lb• ° F) 0.17Flammable Range, % Vol. In Air ( Based On Ashrae Standard 34 With Match Ignition) † † NoneAnsiashrae Standard 36-1992 Safety Group Classification A