PRESERVATION OF COUMAPHOS IN CATTLE DIPPING VATS

A method to prevent the formation of potasan in coumaphos suspensions was tested in cattle dipping vats near the Texas-Mexico border. The su spensions were acidified to below pH 5.5 by the addition of triple sup erphosphate fertilizer (TSP) al the initial charging and the vats were then operated in the usual manner. A vat in Falcon, TX, was used to d ip 4,325 head of cattle over a 396-d period and a vat in Zapata, TX, w as used to dip 2,733 cattle over a 681-d period before they needed to be cleaned and recharged. Potasan, a toxic by-product of coumaphos pro duced by microbial activity, was not formed in either vat. In another study, potasan formed in vats after the addition of TSP was discontinu ed, allowing the pH to increase. Addition of TSP to reduce the pH of t he vat contents to below pH 5.5 quickly prevented further potasan form ation. Although the use of TSP in dipping vats containing coumaphos in creased the rate of sedimentation of active ingredient in freshly made material, this problem was not considered unmanageable and was allevi ated as vats were used.