C - Chemistry – Metallurgy – 07 – C
Patent
C - Chemistry, Metallurgy
07
C
260/597.7
C07C 87/50 (1980.01)
Patent
CA 1173460
-1- HOE 80/F 209 Abstract of the disclosure: The 3,3'-dichloro-4,4'-diamino-biphenyl sulfate obtained in the form of a sulfuric-acid-containing solution from the "benzidine rearrangement" can be converted with good yield to a very pure dihydrochloride by heating the nearly saturated aqueous solution of the sulfate to a temperature in the range of from above 100°C to reflux temperature while adding about 50 to about 70 % of the stoichiometric amount of a chloride-ion-yielding agent, especially hydrochloric acid, subsequently cooling to a temperature in the range of from about 90 to below 100°C, adding further chloride-ion-yielding agent, and cooling to about room temperature. It is especially advantageous to add first the remaining stoichiometric amount of precipitating agent or a slight excess thereof in the temperature range of from about 90 to below 100°C, and a larger excess of up to about twice the stoichiometric amount at a later moment. The dihydrochloride obtained in a well crystallized form is advantageously washed with hydrochloric acid; filtrate and washing water can be easily worked up to hydrochloric and sulfuric acid, respectively. The product is obtained in such a pure state that it can be directly processed to dyeing agents.
386089
Baessler Konrad
Habig Kurt
Fetherstonhaugh & Co.
Hoechst Aktiengesellschaft
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