2,7-Naphthalenedisulfonicacid,4-amino-3-[2-[4'-[2-(2,4-diaminophenyl)diazenyl]-3,3'-dimethyl[1,1'-biphenyl]-4-yl]diazenyl]-5-methyl-6-[2-(4-sulfophenyl)diazenyl]-,sodium salt (1:3)