13011-56-8 2,7-Naphthalenedisulfonic acid, 4-((4-((4-amino-1-naphthalenyl)azo)-1-naphthalenyl)azo)-, disodium salt 4-((4-((4-Amino-1-naphthyl)azo)-1-naphthyl)azo)-2,7-naphthalenedisulfonic acid, disodium salt