Synonyms: calcium bis[2-chloro-5-[(2-hydroxy-1-naphthyl)azo]toluene-4-sulphonate];Pigment Red 53:2;5-chloro-2-[(2-hydroxy-1-naphthalenyl)azo]-4-methyl-benzenesulfonic aci cal;5-chloro-2-[(2-hydroxy-1-naphthalenyl)azo]-4-methyl-benzenesulfonic aci calcium salt;Benzenesulfonic acid, 5-chloro- 2-[(2-hydroxy-1-naphthalenyl)azo]-4-methyl-, calcium salt;Benzenesulfonic acid, 5-chloro-2-[(2-hydroxy-1-naphthalenyl)azo]- 4-methyl, calcium salt;Benzenesulfonic acid,5-chloro-2-[(2-hydroxy-1-naphthalenyl)azo]-4-methyl,calcium salt;Benzenesulfonic acid,5-chloro-2-[(2-hydroxy-1-naphthalenyl)azo]-4-methyl-,calcium salt