7-Hydroxy-8-[[2-methoxy-4-[(4-sodiosulfophenyl)azo]phenyl]azo]naphthalene-1-sulfonic acid sodium salt

2-Aminobenzenesulfonic acid diazo, and O-Anisidine coupling, then the water with sulfonic acid base, again diazotization and with 7-Hydroxynaphthalene-1-sulfonic acid coupling.

blue-ray red. Soluble in water for product red, soluble in ethanol for red orange. The strong sulfuric acid for green light blue, diluted into pink. Adding strong hydrochloric acid in aqueous solution for the red light purple; Add thick sodium hydroxide solution for purple.