Direct measurement of Henry's constant for S-ethyl N,N-di-n-propylthiocarbamate

Many pesticides are susceptible to volatilization, which may result in decreased pest control and off-site deposition that may cause adverse environmental impacts. Prediction of such losses requires knowledge of pesticide partition coefficients, including Henry's constant (H-c); however accurate data are lacking. In this experiment, the batch air stripping technique was used to determine H-c for EPTC (S-ethyl N,N-di-n-propylthiocarbamate). At 25 degrees C, measured H-c in pure water was 0.0107, 11 times greater than indirectly estimated values reported in the literature. The measured heat of volatilization for EPTC, used to describe the temperature dependence of H-c, was 37.12 kJ mol(-1). H-c measured with soil extract was 7 times greater than that measured in pure water, presumably due to effects of dissolved salts and organic acids.