Patent GB-586464-A (GB)
Title: Improvements in or relating to the treatment of crude benzene hexachloride and to compositions containing such treated material
IPC: C07C17/389
Filed: 1944-09-28
Abstract: The objectionable odour associated with crude benzene hexachloride or a solid gammaisomer containing crude fraction thereof is reduced by maintaining the benzene hexachloride in a finely-divided condition in intimate contact with an adsorbent in a divided form, and subsequently separating the benzene hexachloride from the adsorbent solid.  Advantageously, the benzene hexachloride is first ground with a finely-divided inert solid to form a free flowing mixture and the resultant mixture is treated with the adsorbent solid.  Specified adsorbent solids are: silica gel, wood charcoal, animal charcoal, aluminium oxide gel and other amphoteric oxide gels such as stannic oxide gel. Specified inert solids are: water-insoluble solids such as gypsum, slate-dust, china-clay in a non-basic or slightly acidic water-soluble salt, preferably one able to form a solid hydrous material by adsorbing or combining with moisture in crude benzene hexachloride such as a non-basic water-soluble metal salt such as sodium sulphate salt cake, sodium bisulphate, sodium chloride. The preferred adsorbent solid, silica gel may be treated to remove material adsorbed in it by subjecting it to steam distillation or to a temperature of 300 DEG  to 400 DEG  C., or by extracting it with an organic solvent such as acetone, methanol, or carbon tetrachloride. In examples: (1) a mixture of crude benzene hexachloride and silica gel, coarse enough to be retained on such a sieve and preferably on a 20-mesh B.S.S. sieve, is agitated during one half to one day at 10 DEG  to 35 DEG  C.  (2) Wet, crude benzene hexachloride is mixed with from 3 to 5 times its weight of salt cake so as to combine with all the water present, the mixture is ground until it flows freely and all the water is combined with the salt cake; the mixture is agitated with between 5 to 20 per cent of its weight of granular silica gel; the product is sieved through a mesh which retains the silica gel and allows the mixture of benzene hexachloride and salt cake to pass; the salt cake is dissolved out from the mixture by water at either ordinary or elevated temperature, the benzene hexachloride is separated from the resulting sodium sulphate solution, washed and dried; (3) dry benzene hexachloride is treated as in (2) using as diluent either a water-soluble solid such as salt cake or an insoluble one such as gypsum, china clay or slate dust; in the latter event, the extraction step is omitted and the mixture after being sieved to remove adsorbent solid may be used directly in the production of powder - like materials.  Alternatively, the benzene hexachloride may be treated with two or more amounts of adsorbent in succession or in batch countercurrent succession and may be separated from the adsorbent after treatment by mechanical means other than sieving, such as air classification, gravity separation, using a non-solvent liquid intermediate in density between that of benzene hexachloride and silica gel. Specifications 573,689, 573,693, 582,042, [Group I], 586,433, [Group VI], 586,439, 586,442 and 586,450, [Group VI], are referred to.ALSO:Pest control compositions containing purified benzene hexachloride are obtained by the methods of Specifications 573,689, 582,042, [Group I], 586,433 and 586,450, the objectionable odour associated with the crude material having been reduced by maintaining it in a finely divided condition in intimate contact with an adsorbent in a divided form and subsequently separating the benzene hexachloride from the adsorbent solid.  In particular the purified benzene hexachloride may be mixed with an equal weight of dry "Goulac" (Registered Trade Mark) and milled with several times its weight of steel balls from 10 to 20 hours to form a relatively free flowing powder readily dispersible in water.  Prior to purification the material may be mixed with an insoluble diluent, e.g., gypsum, china clay or slate dust.  Specifications 573,693, 586,439 and 586,442, [all in Group IV], also are referred to.