3-hydroxy-4-[(4-sulphonaphthyl)azo]naphthalene-2,7-disulphonic acid 2-Hydroxy-(1,1'-azobisnaphthalene)-3,4',6-trisulfonic acid 3'-Hydroxy[1,4'-azobisnaphthalene]-2',4,7'-trisulfonic acid 3-Hydroxy-4-(4-sulfo-1-naphtylazo)-2,7-naphthalenedisulfonic acid 3-Hydroxy-4-[(4-sulfo-1-naphtyl)azo]naphthalene-2,7-disulfonic acid IRPXADUBAQAOKL-QURGRASLSA-N 2,7-Naphthalenedisulfonic acid, 3-hydroxy-4-[2-(4-sulfo-1-naphthalenyl)diazenyl]-