2,7-Naphthalenedisulfonic acid, 4,5-dihydroxy-3-((8-hydroxy-3,6-disulfo-1-naphthalenyl)azo)-, tetrasodium salt 51053-00-0 51550-25-5 EINECS 257-273-6 Tetrasodium 4,5-dihydroxy-3-((8-hydroxy-3,6-disulphonato-1-naphthyl)azo)naphthalene-2,7-disulphonate