Experimentally and theoretically, Rm depends weakly on temperature and pressure(Hirschfelder etal.,1964). Values of Rm at reference conditions of T ¼ 293.15 K and P ¼ 101.325 kPa are available for hydrocarbons up to C40 (Riazi andMansoori,1993b). For
components that are not liquid under these conditions, Rm was evaluated for the saturated liquid at its normal boiling point. A dimensionless reduced molar refraction was then defined by dividing Rm of a compound to its value for methane: