4,5-dihydroxy-3,6-bis[2-(2-sulfophenyl)diazen-1-yl]naphthalene-2,7-disulfonic acid, 3,6-bis(o-sulfophenylazo)-4,5-dihydroxynaphthalene-2,7-disulfonic acid, 3,6-Bis(o-sulphophenylazo)-4,5-dihydroxynaphthalene-2,7-disulphonic acid, 2,7-Bis-(o-sulfophenylazo)-chromotropsaeure, EINECS 217-089-9,