The apparent solubility in water of several organochlorine insecticides has been examined and found to vary, depending upon the rate of centrifugation of the samples prior to analysis. Samples centrifuged at rates calculated to produce equivalent particle diameters based on Stokes’ law of 0.01, 0.05 and 5.0 microns showed increases of the average concentration in solution for all compounds investigated. The tendency of these slightly soluble organic compounds to form colloidal aggregates and to accumulate at air water interfaces may be partly responsible for changes in concentration. This tendency may be important to physio-chemical and biological reactions that occur in the environment.

Of no less importance is the change in apparent solubility with temperature. As the temperature was increased from 15°C to 45°C, the apparent solubility increased for all compounds investigated. Three- to ten-fold increases in concentration were measured for some compounds when the temperature was increased from 15°C to 45°C. These changes in temperature and the corresponding changes in concentration are considered to have important implications relative to pesticide interactions with soil, water, and biological activity in the environment.