Measurement of vapour pressures of Fenitrothion and Matacil

Vapour pressures of Fenitrothion and Matacil were measured using a gas saturation method. Polyurethane foam was used to trap the volatilized materials from sand and glass surfaces, and Porapak Q for trapping materials volatilized from leaf surfaces. The vapour pressures (VP) were linearly related to the reciprocal temperature by the equation: $\text{Log (VP)}\text{= 6.3362 ? (}\text{3197.8}\text{T}\text{)}$ for a sand incorporated with Fenitrothion and $\text{Log (VP)}\text{= 8.8316 ? (}\text{4021.4}\text{T}\text{)}$ for a sand incorporated with Matacil. The greatest vapour loss rates were from sand incorporated with fenitrothion, followed by vapour loss rates from glass surfaces; the least vapour loss rate was from leaf surfaces.