2-Naphthalenesulfonic acid, 4-hydroxy-6-(methylamino)-3-[[4-(sulfomethyl)phenyl]azo]-, disodium salt

(4-Aminophenyl)methanesulfonic acid??diazo, in alkaline conditions and 4-Hydroxy-6-(methylamino)naphthalene-2-sulfonic acid coupling.

Dark time Soluble in water and ethanol is brown. The strong sulfuric acid for dark orange-red, diluted into palm orange. In water solution to join strong hydrochloric acid for olive brown; Add thick sodium hydroxide solution by red brown into wine red.