Dichlorine hexoxide is the chemical compound with the molecular formula Cl2O6, which is correct for its gaseous state. However, in liquid or solid form, this chlorine oxide ionizes into the dark red ionic compound chloryl perchlorate [ClO2]+[ClO4]−, which may be thought of as the mixed anhydride of chloric and perchloric acids. It is produced by reaction between chlorine dioxide and excess ozone: 2 ClO2 + 2 O3 → 2 ClO3 + 2 O2 → Cl2O6 + 2 O2