Sublimation Vapor Pressures as Evaluated by Correlation-Gas Chromatography

Vapor pressures of the liquid phase obtained by correlation-gas chromatography are used in conjunction with experimental fusion enthalpies to calculate sublimation vapor pressures of a number of compounds including n-alkanes, polyaromatic hydrocarbons, aromatic heterocyclic compounds, and polycyclic hydrocarbons. Vapor pressures at the fusion temperature, T fus, calculated from vapor pressure equations generated by this technique and obtained by extrapolation, are used to evaluate vaporization enthalpies at T fus . The sublimation enthalpy at T fus is obtained from the sum of the experimental fusion enthalpy and vaporization enthalpy. The vapor pressure at T fus, used as an approximation of the triple-point vapor pressure, combined with the sublimation enthalpy and a heat capacity adjustment is used to calculate sublimation vapor pressures as a function of temperature. Calculated sublimation vapor pressures extrapolated to near ambient temperatures compare with experimental values to within a factor of three.