2,2'-[(2,4-dihydroxy-1,3-phenylene)bis(azo-4,1-phenyleneimino)]bis[5-nitro-Benzenesulfonic acid

2,2'-[(2,4-dihydroxy-1,3-phenylene)bis(azo-4,1-phenyleneimino)]bis(5-nitrobenzenesulphonic) acid