disodium 6-hydroxy-5-[(3-sulphonatophenyl)azo]naphthalene-2-sulphonate

3-Aminobenzenesulfonic acid diazo, and 6-Hydroxynaphthalene-2-sulfonic acid coupling.

bright orange. Soluble in water for golden brown, slightly soluble in ethanol for light golden brown. The strong sulfuric acid in orange, orange for gold after diluted. The dye solution to join strong hydrochloric acid for golden brown; Add thick sodium hydroxide solution for red light orange brown.