disodium 4-hydroxy-3-[[2-methoxy-5-[[2-(sulphonatooxy)ethyl]sulphonyl]phenyl]azo]naphthalenesulphonate

4-Hydroxy-3-[[2-methoxy-5-[[2-(sulfooxy)ethyl]sulfonyl]phenyl]azo]-1-naphthalenesulfonic acid disodium salt