Congo Red 696.084 696.667 An indicator dye that is blue-violet at pH 3.0 and red at pH 5.0. Beilstein:3894858 Beilstein:741468 C1=CC(C2=CC=C(N=NC3=CC(=C4C(=C3N)C=CC=C4)S([O-])(=O)=O)C=C2)=CC=C1N=NC5=CC(=C6C(=C5N)C=CC=C6)S([O-])(=O)=O.[Na+].[Na+] C32H22N6Na2O6S2 C32H22N6O6S2.2Na CAS:573-58-0 CHEBI:34653 Congo red Direct red 28 Gmelin:135213 IQFVPQOLBLOTPF-UHFFFAOYSA-L InChI=1S/C32H24N6O6S2.2Na/c33-31-25-7-3-1-5-23(25)29(45(39,40)41)17-27(31)37-35-21-13-9-19(10-14-21)20-11-15-22(16-12-20)36-38-28-18-30(46(42,43)44)24-6-2-4-8-26(24)32(28)34;;/h1-18H,33-34H2,(H,39,40,41)(H,42,43,44);;/q;2*+1/p-2 KEGG:C14078 Kongorot Sodium diphenyldiazo-bis-alpha-naphthylaminesulfonate chebi_ontology disodium 3,3'-((1,1'-biphenyl)-4,4'-diylbis(azo))bis(4-aminonaphthalene-1-sulphonate) disodium 3,3'-(biphenyl-4,4'-diyldidiazene-2,1-diyl)bis(4-aminonaphthalene-1-sulfonate) azo compound