3-[[3,3'-dimethyl-4'-[[4-[[(p-tolyl)sulphonyl]oxy]phenyl]azo][1,1'-biphenyl]-4-yl]azo]-4-hydroxynaphthalene-2,7-disulphonic acid, sodium salt

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