Factors affecting the suspensibility of dieldrin water-dispersible powders.

Various dieldrin water-dispersible powder formulations have been subjected to elevated temperature storage and the effect on their suspensibilities compared. The Shell Chemical Company's 50% dieldrin formulation AC 1630 was recommended for use in the malaria control programmes of the International Cooperation Administration rather than its 50% formulation AC 1631, on the basis of superior performance after storage at 50 degrees C and 65 degrees C. In a similar series of tests on 75% dieldrin water-dispersible powders, Shell formulation AC 1621, which contains Hi-Sil as diluent, was judged better than AC 6621, which contains Micro-Cel as diluent. A series of samples of AC 1621 was subjected to temperatures of 90-120 degrees C for periods of 1-20 hours and the effect on suspensibility determined. Most samples withstood the treatment reasonably well at temperatures up to 110 degrees C for 20 hours.