2,7-Naphthalenedisulfonic acid, 4,5-dihydroxy-3-[(4-nitrophenyl)azo]-, disodium salt 548-80-1 C.I. 16575 C.I. Acid Red 176 C.I. Acid Red 176, disodium salt Chromatrope 2B Chromotrope 2B Chromotrope Red 4B Khromotrop 2B NSC45542 Naphtocard Fast Red 3B p-Nitrobenzeneazochromotropic acid sodium salt