5-amino-4-hydroxy-3-[(2-hydroxy-3-nitro-5-sulphophenyl)azo]naphthalene-2,7-disulphonic acid, sodium salt

5-Amino-4-hydroxy-3-[(2-hydroxy-3-nitro-5-sulfophenyl)azo]-2,7-naphthalenedisulfonic acid/sodium,(1:x) salt