tetrasodium 4,4'-bis[[2-methoxy-5-methyl-4-[(4-sulphonatophenyl)azo]phenyl]-N,N,O-azoxy]stilbene-2,2'-disulphonate

2,2'-(1,2-Ethenediyl)bis[5-[[2-methoxy-5-methyl-4-[(4-sulfophenyl)azo]phenyl]-NNO-azoxy]benzenesulfonic acid]tetrasodium salt