PURPOSE:To purify the titled compound useful in dye industry, in high purity, with simple method, without lowering the yield, by adding concentrated sulfuric acid to a reaction mixture containing the titled compound to extract and separate the objective material, diluting the extract with water, and separating the precipitated crystals. CONSTITUTION:A reaction mixture obtained by sulfonating 1,4-diaminoanthraquinone in an inert organic solvent is mixed with concentrated or fuming sulfuric acid to extract and separate 1,4-diaminoanthraquinone-2-sulfonic acid to the sulfuric acid layer. The concentration of the sulfuric acid and that of the fuming sulfuric acid used in the extraction are pref. 80-100wt% and =10wt%, respectively. The extracted liquid is diluted with water or dilute sulfuric acid to lower the sulfuric acid concentration to 15-75%, and the precipitated crystals are filtered to obtain the titled compound in high purity.
展开▼
