has role is protonated form of independent continuant azobenzenes benzamides naphthols naphthalenesulfonic acid bis(azo) compound fluorochrome poison histological dye environmental contaminant Sirius red 4B (acid form) CHEBI:88192 A naphthalenesulfonic acid that is 7-amino-4-hydroxy-3-({4-[(4-sulfophenyl)diazenyl]phenyl}diazenyl)naphthalene-2-sulfonic acid in which one of the amino hydrogens is replaced by a benzoyl group. The disodium salt is the histological dye 'Sirius red 4B'. Sirius red 4B(2-)