4-hydroxy-5-[(2-hydroxy-1-naphthyl)azo]-3-[(2-hydroxy-3-nitro-5-sulphophenyl)azo]naphthalene-2,7-disulphonic acid, sodium salt

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