2,7-Naphthalenedisulfonic acid, 3-[(4-aminophenyl)azo]-4-hydroxy-5-[[(4-methylphenyl)sulfonyl]amino]-, disodium salt

(a) N-(3-aminophenyl)acetamide diazo, and 8-(4-Methylphenylsulfonamido)-1-naphthol-3,6-disulfonic acid coupling, hydrolysis acetyl groups; (b) 4-Nitrobenzenamine diazo, and 8-(4-Methylphenylsulfonamido)-1-naphthol-3,6-disulfonic acid coupling, and then will the nitro reduction.

red light blue. Soluble in water for red purple. The strong sulfuric acid for red, diluted the same color. In water solution to join strong hydrochloric acid for brick red; Add 10% sodium hydroxide solution for blu-ray red. The sun fastness medium.