16589-20-1 2,7-Naphthalenedisulfonic acid, 5-amino-3-((4-((1,8-dihydroxy-3,6-disulfo-2-naphthalenyl)azo)phenyl)azo)-4-hydroxy-, tetrasodium salt 2,7-Naphthalenedisulfonic acid, 5-amino-4,4',5'-trihydroxy-3,3'-(p-phenylenebis(azo))di-, tetrasodium salt Hydrotypic Blue