Acid Red 231

N-(4-aminophenyl)acetamide diazo, and 6-Amino-4-hydroxynaphthalene-2-sulfonic acid? in acid conditions coupled.

dark blue light red. Soluble in water for orange, red for the strong sulfuric acid in purple, diluted red for blue-ray. In aqueous solution to join strong hydrochloric acid, a red brown precipitation; In the thick sodium hydroxide solution of color.