4-Hydroxy-3-[(4-methoxy-2-sulfophenyl)azo]-6-[methyl[[2-(sulfooxy)ethyl]sulfonyl]amino]-2-naphthalenesulfonic acid trisodium salt

trisodium 4-hydroxy-3-[(4-methoxy-2-sulphonatophenyl)azo]-6-[methyl[[2-(sulphonatooxy)ethyl]sulphonyl]amino]naphthalene-2-sulphonate