b CIRCULAR 9 7 7, U. S. DEPARTMENT OF AGRICULTURE 



Methoxychlor is effective in space sprays and residual treatments 

 against house flies. It is less toxic than DDT to warm-blooded animals, 

 and is not stored in animal fat to the same extent. TDE has given 

 good results as a mosquito larvicide. It is slightly less toxic than 

 DDT to the larvae but is also less toxic to fish and mammals. Neither 

 of these insecticides is available as a military-issue item. 



BENZENE HEXACHLORIDE 

 Properties 



Benzene hexachloride (BHC) was first prepared by Michael Faraday 

 in 1825. Its insecticidal properties apparently were first investigated 

 in France in 1940 and in England in 1942. A French patent was issued 

 to A. Dupire in 1941. This chemical was designated in England as 

 666 from its molecular formula C 6 H 6 C1 6 . The chemical name is 

 1,2,3,4,5,6-hexachloroeyclohexane. It is prepared by the chlorination 

 of benzene in the presence of ultraviolet light. 



The crude material contains five known stereoisomers. The gamma 

 isomer, which is the most toxic to insects, constitutes only about 12 

 percent of the product and the alpha isomer 60 to 70 percent. Partly 

 refined products containing from 36 to 90 percent of the gamma isomer 

 are available, and also a refined product consisting of nearly pure 

 gamma. 



Gammexane is a proprietary name that originated in England and 

 has appeared in European literature for the gamma isomer. Lindane 

 is the common name that has been approved by the U. S. Interdepart- 

 mental Committee on Pest Control for a product containing not less 

 than 99 percent of the gamma isomer. It is considerably more 

 expensive to produce than the partly refined material but is coming 

 into extensive use because of its high toxicity to many economic 

 species. 



The crude and partly refined materials have a pronounced musty 

 odor. In the pure gamma isomer, however, the odor is much reduced, 

 and the product is emploj'ed in household sprays in many countries, 

 including the United States. 



Gamma benzene hexachloride is a white crystalline material, is 

 very stable to oxidation, and has a melting point of 112.5° C. It 

 has the following structural formula: 



ci 



ii 



ci 



H 



It is nearly insoluble in water and is less soluble than DDT in most 

 petroleum oils and other solvents. Its solubilities in some common 

 solvents are as follows: 



