| 摘要 |
of the disclosure HOE 89/F 358 Process for the continuous preparation of 3,3'-dichloro-benzidine dihydrochloride A process for the continuous preparation of 3,3'-di-chlorobenzidine dihydrochloride from 2,2'-dichlorohydra-zobenzene by treatment with aqueous sulfuric acid, which comprises treating the 2,2'-dichlorohydrazobenzene, dissolved in a water-immiscible aromatic solvent, continuously at temperatures of from about 20 to about 50.degree.C in the presence of an alkali metal salt of an alkyl (C8-C23)polyglycol ether sulfate, with such an amount of from about 50 to about 80 % strength aqueous sulfuric acid that the suspension formed remains conveyable, subsequently diluting the suspension emerging from the reaction zone with water, again continuously, and subsequently heating the suspension to a temperature of from about 90 to about 95.degree.C until a solution is obtained, separating off the aromatic solvent from the hot, sulfuric acid aqueous phase, and precipitating the 3,3'-di-chlorobenzidine dihydrochloride by adding hydrochloric acid to the sulfuric acid solution which remains and filtering off this product.
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