tetrasodium 5,5'-[vinylenebis[(3-sulphonato-4,1-phenylene)azo]]bis(salicylate)

Preparation

1,2-Bis(4-amino-2-sulfophenyl)ethene double nitriding, and 2-Hydroxybenzoic acid (2 Moore) coupled.

Properties and Applications

dark red light yellow to orange. Soluble in water for yellow orange, slightly soluble in alcohol. The strong sulfuric acid to red light purple, dilute for dark brown or black after; In nitric acid solution for light yellow, with gray precipitation. The dye solution to join strong hydrochloric acid for dark brown, have precipitation; Add thick sodium hydroxide solution in red.