2,7-Naphthalenedisulfonicacid,4-amino-3-[2-[4′-[2-(2,4-dihydroxyphenyl)diazenyl]-3,3′-dimethyl[1,1′-biphenyl]-4-yl]diazenyl]-5-hydroxy-6-[2-(4-sulfophenyl)diazenyl]-