Thermodynamics Research Center / ThermoML | Journal of Chemical and Engineering Data

ABSTRACT

This work reports experimental sublimation and vaporization vapor pressures at different temperatures of the three isomers of hydroxybenzaldehyde. A static method based on capacitance diaphragm manometers was used to measure the vapor pressures of both (crystalline and liquid) condensed phases of ortho, meta, and para hydroxybenzaldehydes, through the temperature ranges T = (264.6 to 341.7) K, T = (324.9 to 419.4) K, and T = (334.9 to 429.4) K, respectively. The Knudsen mass-loss effusion technique was also used to determine the vapor pressures of crystalline meta and para isomers in the temperature intervals T = (309.1 to 331.2) K and T = (319.1 to 341.2) K, respectively. The obtained results enabled the determination of the standard molar enthalpies and entropies of sublimation and of vaporization, at chosen reference temperatures, as well as the (p,T) values of the triple point of the compounds studied. The temperatures and enthalpies of fusion were determined from differential scanning calorimetry. The contributions of the formyl group to the sublimation properties of benzaldehydes were determined, and the standard Gibbs energies of formation in condensed and gaseous phases were calculated.