Compositions of 1,1,1,3,3 - pentafluoropano and 2 - metilbutano analogas the azeotroposAn azeotropic compsn. comprises: (a) 65-81 wt.%1,1,1,3,3-pentafluoropropane; and (b) 19-35 wt.% 2-methyl butane, where the compsn. has a b.pt. of about 7 deg C at 1 atmos.. ...