Gamma benzene hexachloride dusts

Dusting-powder of Gamma Benzene Hexachloride and Pyrethrum, J5.P.C. Contains 2 per cent of extract and is assayed for pyrethrins by the method given below for Dusting-powder of Pyrethrum. 

LaClair (43) has employed the dehydrohalogenation reaction to determine the gamma isomer of benzene hexachloride in the technical product and in dust mixtures. Two identical samples are dissolved in 95% ethyl alcohol and treated with 1 N ethanolic potassium hydroxide at 0° C. for 15 and 50 minutes, respectively. The 15-minute period is sufficient to dehydrochlorinate most of the alpha and the delta isomers without appreciably affecting the gamma. In 50 minutes the gamma isomer is also dehydrochlorinated. The beta isomer does not react under these conditions, and usually the epsilon isomer is present in quantities too small to interfere seriously. 

It was also established in laboratory work that this product could be readily formulated into dusts, wettable powder, or liquid formulations. Liquid formulations were more readily made with this than with the commercial benzene hexachloride, because of the higher concentration of the gamma isomer. 

The residual toxicity of the pure gamma isomer was found to be equivalent to that of ordinary commercial benzene hexachloride. Commercial usage has shown that the residual action is effective for a longer time with dust or wettable powder spray applications than with emulsive solvent-type formulations. The over-all residual life of the chemical is on the order of 4 to 8 days as compared to 14 to 21 days for DDT. This is, of course, adequate residual life for good insect control in most cases and the shorter... 

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