4-[[4-[(2-hydroxy-1-naphthyl)azo]phenyl]azo]benzenesulphonic acid

4-[[4-[(2-Hydroxynaphthalen-1-yl)azo]phenyl]azo]benzenesulfonic acid

4-[[4-[(2-Hydroxy-1-naphthalenyl)azo]phenyl]azo]benzenesulfonic acid