Definition of chlorine trioxide in US English:

chlorine trioxide


  • 1An oxide of chlorine (dichlorine trioxide), Cl₂O₃, which is a brown crystalline substance at low temperatures and is explosively unstable.

  • 2A dark red oxide of chlorine formed by the reaction of chlorine dioxide and ozone, existing as a dimeric gas, Cl₂O₆, or as an ionic liquid or solid, [ClO₂ +ClO₄ −] (dichlorine hexoxide.).


Mid 19th century.