tetralithium 7,7'-(carbonyldiimino)bis[4-hydroxy-3-[(6-sulphonato-2-naphthyl)azo]naphthalene-2-sulphonate]

7,7'-(Carbonyldiimino)bis[4-hydroxy-3-[(6-lithiooxysulfonyl-2-naphthalenyl)azo]-2-naphthalenesulfonic acid lithium] salt