3-[(4-Formylphenyl)azo]-4,5-dihydroxy-2,7-naphthalenedisulfonic acid disodium salt

4-Aminobenzaldehyde diazo, and 4,5-Dihydroxynaphthalene-2,7-disulfonic acid?coupling.

colourful red blue light. Soluble in water is red. The strong sulfuric acid in blue, diluted into red; In the bright red precipitation appear in the hydrochloric acid; Sodium hydroxide solution for deep in the red.

Standard	Light Fastness	Soaping		Persperation Fastness	Oxygen bleaching		Fastness to seawater
		Fading	Stain		Fading	Stain	Fading	Stain
ISO	5	3	3	2	4-5