Preparation
2-Amino-5-methylbenzene-1,4-disulfonic acid diazo, and 5-Aminonaphthalene-2-sulfonic acid and 8-Aminonaphthalene-2-sulfonic acid coupling, again diazo, and Naphthalen-1-amine coupling, its product to diazo, in alkaline conditions and 4-Hydroxy-7-(phenylamino)naphthalene-2-sulfonic acid coupling.
