disodium 4-[[2,4-dihydroxy-3,5-bis(phenylazo)phenyl]azo]-5-hydroxynaphthalene-2,7-disulphonate

4-[[2,4-Dihydroxy-3,5-bis(phenylazo)phenyl]azo]-5-hydroxy-2,7-naphthalenedisulfonic acid disodium salt