A simple generalized equation for the enthalpy of vaporization (lambda/RTC) = (7 + 11 omega(E))(1 - T-R)((3/8)) where lambda is the enthalpy of vaporization (J/g mol), R is the gas constant (= 8.3144 J/g mol K), T-C is the critical temperature (K) and omega(E) is the acentric factor according to Edmister＇s rule, has been formulated and tested.