Synonyms: 3-[[4-[(7-Amino-1-hydroxy-3-sulfo-2-naphthalenyl)azo]-1-naphthalenyl]azo]-2,6-dihydroxybenzoic acid disodium salt;C.I.Direct Black 51;Direct Fast Grey BN;3-[4-[1-Hydroxy-3-(sodiooxysulfonyl)-7-aminonaphthalene-2-ylazo]naphthalene-1-ylazo]-2,6-dihydroxybenzoic acid sodium salt;c.i.direct black 51;