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



Methods of Analysis 



The total-chlorine determination as described for DDT (p. 5) may 

 also be used for the assay of benzene hexachloride, although it is of 

 value only when it is known that this is the only chlorine compound 

 present. The total-chlorine determination does not give any indi- 

 cation as to the gamma-isomer content. However, it may be used 

 for the determination of lindane under the same conditions as for 

 BHC — i. e., it is not specific. The factor for total BHC and for 

 lindane from the total-chlorine content is 1.3665. 



The labile, or hydrolyzable, chlorine determination as reported for 

 DDT (p. 5) may also be used for BHC and lindane, although again 

 the method is not specific. The factor for calculating BHC and 

 lindane is 2.7330. 



An infrared spectrometric method (Daasch 4) may be used to 

 determine the gamma-isomer content, as well as that of the other 

 isomers in technical BHC in the absence of more than very small 

 quantities of other chlorinated cyclohexanes. 



The gamma-isomer content of technical BHC and of formulations 

 containing it is determined by the partition-chromatographic method 

 (Harris 7), in which this isomer is separated from the other com- 

 ponents by passing a hexane-nitromethane solution of the sample 

 through a silicic acid column. The BHC isomers are eluted with 

 the hexane-nitromethane solution. The solvent is removed by 

 evaporation from that portion of the eluate containing the gamma 

 isomer, and the gamma isomer is weighed. 



The gamma isomer may also be determined by polarography 

 (Dragt 6). This is the only isomer that is reduced at the dropping- 

 mercury electrode under the conditions stipulated in the methods 

 used. 



A simple cryoscopic method (Toops and Riddick 14) for deter- 

 mining the gamma-isomer content of BHC has been refined, and since 

 it has an accuracy of ±0.05 percent it is of value for the character- 

 ization and determination of lindane. 



A sensitive colorimetric method (Schechter and Hornstein 12) for 

 determining small quantities of BHC has been devised. It is based 

 on the dechlorination of this compound to benzene by means of zinc 

 and acetic acid with subsequent nitration of the benzene and reaction 

 with 2-butanone in the presence of strong alkali to give a violet-red 

 color that may be measured photometrically. The method is not 

 specific for lindane. 



CHLORDANE AND HEPTACHLOR 

 Properties 



The effectiveness of chlordane as an insecticide was announced by 

 Kearns and associates (10) in 1945. It was referred to as 1068 from 

 its molecular formula Ci H 6 Cl 8 . It has also been called Octa-Klor. 

 Its chemical name is l,2,4,5,6,7,8,8-octachloro-2,3,3a,4,7,7a-hexa- 

 liv(li'o-4,7-methanoindene. Technical chlordane contains 60 to 70 

 percent of chlordane and 25 to 40 percent of related compounds 

 occurring in the normal manufacturing processes. 



Chlordane is a viscous amber liquid, with a boiling point of 175° C. 

 at 2-mm. pressure. The technical product has a specific gravity of 



