DIRECT MEASUREMENT OF HENRYS 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 o f pesticide partition coefficients, including Henry's constant (H-c); however accurate data are lacking. In this experiment, the batch air s tripping 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 wa s 0.0107, 11 times greater than indirectly estimated values reported i n the literature. The measured heat of volatilization for EPTC, used t o 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.