4-chloro-5-hydroxynaphthalene-2,7-disulphonic acid 8-chloro-1-naphthol-3,6-disulfonic acid 4-Chloro-5-hydroxy-2,7-naphthalenedisulfonic acid 4-chloro-5-hydroxy-naphthalene-2,7-disulfonic acid 4-chloro-5-hydroxynaphthalene-2,7-disulfonic acid 2,7-Naphthalenedisulfonic acid, 4-chloro-5-hydroxy-