3-[[4-[[4-[ethyl[(4-sulphophenyl)methyl]amino]phenyl]azo]-1-naphthyl]azo]benzenesulphonic acid, sodium salt

3-[[4-[[4-[Ethyl[(4-sulfophenyl)methyl]amino]phenyl]azo]-1-naphthalenyl]azo]benzenesulfonic acid/sodium,(1:x) salt