Improvements in or relating to benzene hexachloride

Benzene hexachloride enriched in gamma isomer is made by additively chlorinating benzene in the liquid phase at a temperature not exceeding 70 DEG C. until a slurry is formed, in which at least 80 per cent by weight of the gamma isomer is in the liquid phase, raising the temperature to dissolve at least 2 per cent by weight of the solid phase, cooling at a rate not in excess of 12 DEG C. per hour, preferably at a rate between 2 DEG C. and 12 DEG C. per hour, to reprecipitate dissolved solids, but not beyond the point at which 20 per cent by weight of gamma isomer will precipitate, removing the solid phase from the cooled slurry, e.g. by centrifuging, and recovering gamma enriched benzene hexachloride from the liquid phase. In an example, benzene is chlorinated at 24-25 DEG C. under irradiation with actinic light, at the conclusion of the chlorine addition the temperature of the reaction slurry is allowed to rise to 51.5 DEG C., after 1-2 hours at this temperature the mixture is cooled to 15-19 DEG C. over a period of 4-7 hours, the solids are removed by centrifuging and the gamma enriched fraction is recovered from the liquid phase by distilling off the benzene.