sodium 3-[[2,2'-dimethyl-4'-[[4-[(phenylsulphonyl)oxy]phenyl]azo][1,1'-biphenyl]-4-yl]azo]-4-hydroxynaphthalene-2,7-disulphonate

3-[[2,2'-Dimethyl-4'-[[4-[(phenylsulfonyl)oxy]phenyl]azo][1,1'-biphenyl]-4-yl]azo]-4-hydroxy-2,7-naphthalenedisulfonic acid/sodium,(1:x) salt