5-[[2-Methoxy-5-methyl-4-[(4-sulfophenyl)azo]phenyl]-NNO-azoxy]-2-[2-(4-nitro-2-sulfophenyl)ethenyl]benzenesulfonic acid trisodium salt

trisodium 5-[[2-methoxy-5-methyl-4-[(4-sulphonatophenyl)azo]phenyl]-N,N,O-azoxy]-2-[2-(4-nitro-2-sulphonatophenyl)vinyl]benzenesulphonate