On prolonged chlorination of phthalic anhydride at 170-265'in the presence of ferric chloride'a weight increase greater than that corresponding to the formation of the tetrachloro derivative is observed, and finally the weight decreases again, while carbon dioxide and phosgene (identified as diphenylurea) are being evolved. The final product, obtained in 95% yield, is hexachlorobenzene. The formation of hexachlorobenzene from unsym- ...
