tetrasodium 4,4'-[carbonylbis[imino(5-dimethoxy-2-methyl-4,1-phenylene)azo]]bisnaphthalene-2,7-disulphonate

4,4'-[Carbonylbis[imino(5-methoxy-2-methyl-4,1-phenylene)azo]]bis[2,7-naphthalenedisulfonic acid]tetrasodium salt