1,5-Naphthalenedisulfonic acid, 2-((8-(((2,3-dichloro-6-quinoxalinyl)carbonyl)amino)-1-hydroxy-3,6-disulfo-2-naphthalenyl)azo)-, tetrasodium salt 4-(((2,3-Dichloro-6-quinoxalinyl)carbonyl)amino)-5-hydroxy-6-((1,5-disulfo-2-naphthyl)azo)-2,7-naphthalenedisulfonic acid, tetrasodium salt 72639-31-7