6-[[[2-(diethylamino)ethyl]sulphonyl]methylamino]-4-hydroxy-3-[(4-methoxy-2-sulphophenyl)azo]naphthalene-2-sulphonic acid, sodium salt

6-[[[2-(Diethylamino)ethyl]sulfonyl]methylamino]-4-hydroxy-3-[(4-methoxy-2-sulfophenyl)azo]-2-naphthalenesulfonic acid/sodium,(1:x) salt