Critical Micelle Concentration and Surface Tension of Surfactant in Liquid Insecticides

The surface tension of 30 insecticides with conventional concentration was measured with the method in national standard(GB 5549 90)in laboratory and the critical micelle concentration(CMC) of surfactant of each insecticide was measured according to the change of surface tension of the insecticide.The CMC of surfactant 885,and the changes of the surface tension of the same concentration of 885 with the area of gas liquid were measured,too.The surfactant did not reach the CMC in most liquid insecticides with conventional concentration,and the concnetration of some insecticides was 10 times more than conventional concentration when the surfactant was the same as the CMC.The CMC was changed as the area of gas liquid was increased largely,at the same time,the surface tension was inhanced.For good effectiveness to pests,the concentration of surfactant in the liquid insecticides with conventional concentration must be more than the CMC.