Abstract :
The base 10 logarithm of vapour pressure for each of 39 structural classes of hydrocarbons and substituted hydrocarbons is a linear function of carbon number, and a cubic polynomial of temperature. These functions may be used to estimate the vapour pressures of compounds for which no laboratory measurements are available. Comparison of the resulting vapour pressure predictions with field measurement data of organic particulates has suggested that vapour pressures lower than approximately 5E−05 mm Hg are necessary for low-solubility compounds to partition significantly to particulates. Soluble compounds may enter the particle phase at much higher vapour pressures. A hierarchy of species’ likelihood to partition to the particulate phase, based on vapour pressure, has been suggested for the compounds studied, from diacids being the most likely to partition, to iso-alkyl ketones as the least likely to partition.
