2,7-Naphthalenedisulfonic acid, 4-((3-((3-amino-4-nitrophenyl)azo)-2,4-dihydroxyphenyl)azo)-5-hydroxy-, disodium salt 5-((3-((3-Amino-4-nitrophenyl)azo)-2,4-dihydroxyphenyl)azo)-4-hydroxy-2,7-naphthalenedisulfonic acid, disodium salt 72894-23-6