Abstract: The cubic equation of state was used to predict the vapor pressure of pure compounds at the specified temperature at which vapor-liquid equilibrium occurred. The equation of state was solved using the programs, in which the vapor pressure was reported when the critical properties as the critical pressure, critical temperature and acentric factor were specified. The vapor pressures of more than 400 compounds in gasoline were calculated by SRK or PR EOS. The predictions of vapor pressure of some hydrocarbon compounds at 37.8℃are in good agreement with the observations. The average relative error is lower than 1% for the light compounds, and lower than 4% for all the compounds in full range gasoline.

Key words: gasoline fraction, hydrocarbon, equation of state