| IUPAC name
| Preferred IUPAC name
| Systematic IUPAC name
| Other names
|Molar mass||67.45 g/mol|
|Appearance||Yellow to orange gas|
|Melting point||−59 °C (−74 °F; 214 K)|
|Boiling point||11 °C (52 °F; 284 K)|
|8 g/L (at 20 °C)|
|Solubility||Soluble in alkaline and sulfuric acid solutions|
|Vapor pressure||>1 atm|
Std enthalpy of
|Safety data sheet||Ecosense Company|
|Lethal dose or concentration (LD, LC):|
LD50 (Median dose)
|292 mg/kg (oral, rat)|
LC50 (Median concentration)
|260 ppm (rat, 2 hr)|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Chlorine dioxide is a chemical compound with the formula ClO2.
Chlorine dioxide does not hydrolyze when it is absorbed in water and remains a dissolved gas in solution. Chlorine dioxide is approximately 10 times more soluble in water than chlorine.
Chlorine dioxide has been known to spontaneously explode when exposed to sunlight/UV light. It lacks an upper explosive limit, so it can explode under any concentration.
Chlorine dioxide is a yellowish gas, with an acrid odor, very reactive, very soluble in water.
Chlorine dioxide is not sold and has to be made in situ.
Chlorine dioxide is a compound that can decompose extremely violently when separated from diluting substances. As a result, preparation methods that involve producing solutions of it without going through a gas-phase stage are often preferred.
In the laboratory, ClO2 can be prepared by oxidation of sodium chlorite with chlorine:
- 2 NaClO2 + Cl2 → 2 ClO2 + 2 NaCl
Addition of hydrochloric acid to sodium chlorite, in the presence of sodium hypochlorite also yields this compound. The reaction will also work if only sodium chlorite and HCl alone are used.
- 2 NaClO2 + 2 HCl + NaOCl → 2 ClO2 + 3 NaCl + H2O
- 5 NaClO2 + 4 HCl → 5 NaCl + 4 ClO2 + 2 H2O
- 2 KClO3 + 2 H2C2O4 → K2C2O4 + 2 ClO2 + 2 CO2 + H2O
- 2 KClO3 + H2C2O4 + 2 H2SO4 → 2 KHSO4 + 2 ClO2 + 2 CO2 + 2 H2O
- Bleaching of wood pulp
- Disinfection (water chlorination)
- Light sensitive reaction demonstration
Chlorine dioxide is highly reactive and corrosive. The gas can explode under the effect of sunlight, if present in a transparent container. The United States Environmental Protection Agency has set a maximum level of 0.8 mg/L for chlorine dioxide in drinking water.
Cannot be safely stored.
Gaseous form should be released in air in remote areas. Solutions can be neutralized with a reducing agent.