3-[[4-[(4-amino-7-sulpho-1-naphthyl)azo]-7-sulpho-1-naphthyl]azo]naphthalene-1,5-disulphonic acid, sodium salt

3-[[4-[(4-Amino-7-sulfo-1-naphthalenyl)azo]-7-sulfo-1-naphthalenyl]azo]-1,5-naphthalenedisulfonic acid/sodium,(1:x) salt