7,7'-Iminobis(4-hydroxy-2-naphthalenesulfonic acid) 5,5'-dihydroxy-2,2'-dinaphthylamine-7,7'-disulphonic acid 4,4'-Dihydroxy-7,7'-iminodi(naphthalene-2-sulfonic acid) Rhoduline acid 4,4'-dihydroxy-7,7'-iminodi(naphthalene-2-sulphonic acid) N,N-Bis(5-naphthol-7-sulfonic acid)amine 6,6'-Iminobis(1-hydroxynaphthalene-3-sulfonic acid) 4-hydroxy-7-[(5-hydroxy-7-sulfo-2-naphthyl)amino]naphthalene-2-sulfonic acid