8-[4'-(p-Hydroxyphenylazo)-3,3'-dimethyl-4-biphenylylazo]-7-hydroxy-1,3-naphthalenedisulfonic acid

7-hydroxy-8-[[4'-[(4-hydroxyphenyl)azo]-3,3'-dimethyl[1,1'-biphenyl]-4-yl]azo]naphthalene-1,3-disulphonic acid