Vapor Pressures and Surface Free Energies of C14-C18 Monocarboxylic Acids and C5 and C6 Dicarboxylic Acids

Vapor pressures and surface energies of C14-C18 monocarboxylic acids and C5 and C6 dicarboxylic acids in the 10–50 °C range are reported. Mass-transfer theory was used to determine vapor pressure and surface energy values from measured evaporation rates of monodisperse aerosol particles. Measurements were done with particles in the 0.015-0.25-μm-diameter range, where surface energies have a significant effect on evaporation rates. The functional dependencies of vapor pressures on temperature are consistent with the Clausius-Clapeyron equation. Also, vapor pressures are found to have a simple dependence on the number of carbon atoms per molecule. Measured vapor pressures ranged from <10^-5 to ~10^-2 Pa. Temperature-dependent surface energies for these species, which are solid in the 10–50 °C range, varied from 0.020 to 0.450 J/m² and increased systematically with decreasing temperature.