3-hydroxy-4-[[4-[[4-[(2-hydroxy-6-sulpho-1-naphthyl)azo]-o-tolyl]methyl]-m-tolyl]azo]naphthalene-2,7-disulphonic acid, sodium salt

2,7-Naphthalenedisulfonic acid, 3-hydroxy-4-4-4-(2-hydroxy-6-sulfo-1-naphthalenyl)azo-2-methylphenylmethyl-3-methylphenylazo-, sodium salt