tetrasodium 5,5'-[thiobis[(3-sulphonato-p-phenylene)azo]]disalicylate

2-(2-Sulfo-4-aminophenylthio)-5-aminobenzenesulfonic acid double nitriding, and 2-Hydroxybenzoic acid (2 Moore) coupled.

red light yellow. Soluble in water for red light yellow to orange, soluble in ethanol. In the strong sulfuric acid to red, yellow for green light after diluted. The dye solution to join strong hydrochloric acid for olive brown, have precipitation; Add thick sodium hydroxide solution for orange brown.