Substance profile
Chlorine Dioxide
Chlorine Dioxide is a yellowish-brown gas with an unpleasant odor similar to chlorine and nitric acid.
01 · Identification
What Chlorine Dioxide is
Chlorine Dioxide is a yellowish-brown gas with an unpleasant odor similar to chlorine and nitric acid. Its molecular formula is ClO2 and its molecular weight is 67.45 g/mol. It boils at 11 °C, melts at -59 °C.
Under the GHS it carries the signal word Danger. It is classed as flammable agents - 4th degree.
02 · GHS classification
Hazards and label elements
Harmonised classification under CLP Annex VI. This is the legally binding classification in the EU; other jurisdictions may differ.
| Code | Hazard statement |
|---|---|
| H270 | May cause or intensify fire; oxidiser. |
| H330 | Fatal if inhaled. |
| H314 | Causes severe skin burns and eye damage. |
| H400 | Very toxic to aquatic life. |
Precautionary statements: P260, P271, P273, P280, P301, P304, P310, P331, P391, P501
03 · Physical and chemical properties
Chlorine Dioxide properties
Every value is shown with the conditions it was measured under and the source it came from. Where sources disagree, all values are listed rather than one being picked — the difference is usually a different form of the substance, not an error.
| Property | Value | Conditions | Source |
|---|---|---|---|
| Boiling point | 11 °C (51.8 °F) | HSDB | |
| 11.11 °C (52 °F) | NIOSH | ||
| 11.11 °C (52 °F) | at 760 mmHg | CAMEO | |
| Melting point | -59 °C (-74.2 °F) | HSDB | |
| -58.89 °C (-74 °F) | NIOSH | ||
| Density | 1.77 g/cm³ | HSDB | |
| 3.09 g/cm³ | at 11 °C | DOE PAC | |
| 1.642 g/cm³ | at 0 °C, liq | HSDB | |
| Solubility | 2000 cc (gas) in 100 cc cold water | HSDB | |
| In water, 1.823X10-2 at 298.15 K | HSDB | ||
| Soluble in water | HSDB | ||
| Vapor pressure | 757.562 mmHg | at 20 °C | HSDB |
| 760 mmHg | above this value | NIOSH | |
| Flash point | NA (Gas) ? (Liquid) | NIOSH | |
| Vapor density | 2.3 (air = 1) | HSDB | |
| 2.33 (air = 1) | CAMEO | ||
| Odor threshold | Odor Threshold Low: 0.1 [ppm] | Haz-Map | |
| Odor Threshold High: 15.0 [ppm] | Haz-Map | ||
| [ACGIH] Odor threshold from NJ "Hazardous Substance Fact Sheet" | Haz-Map | ||
| Critical temperature and pressure | Critical temperature: 465K; critical pressure: 8621.6 kPa | HSDB |
Values compiled from PubChem Laboratory Chemical Safety Summary. Temperatures converted to Fahrenheit for reference.
04 · Fire and explosion
Fire and explosion behaviour of Chlorine Dioxide
These are descriptions rather than measured values, so they are kept out of the table above and quoted here with the source that reported them.
Fire and explosion
/Chlorine dioxide/ is explosive above 45 °C even in absence of light, and subject to long induction periods due to formation of intermediate dichlorine trioxide.
Source: HSDB
With over 10% chlorine dioxide in air at pressures from 0.1 to 1.0 atmosphere, chlorine dioxide is violently explosive. Explosion may be initiated by almost any form of energy such as sunlight, heat, or sparks.
Source: HSDB
A powerful explosive sensitive to spark, impact, sunlight, or heating rapidly to 100 °C. ... Concentrations of greater than 10% in air are explosive. Explodes on mixing with carbon monoxide, hydrocarbons (e.g., butadiene, ethane, ethylene, methane, propane), fluoramines (e.g. difluoramine, trifluoramine). Mixtures with hydrogen explode with sparking or contact with platinum. Explodes on contact with mercury, potassium hydroxide, phosphorous pentachloride + chlorine. Ignites or explodes on contact with non-metals (e.g., phosphorous, sulfur, sugar).
Source: HSDB
05 · Handling and storage
Storing and handling Chlorine Dioxide
Storage conditions
Store separately from all other flammable materials. Prior to working with chlorine dioxide you should be trained on its proper handling and storage. This chemical is a powerful oxidizer, and is shock-, light- and heat sensitive. It is violently explosive in air at concentrations over 10%. Keep frozen when not in use. Store in tightly closed containers in a cool, dark, well-ventilated area at temperatures well below 130 °C. Gas explosions may occur above 130 °C. Use only nonsparking tools and equipment, especially when opening and closing containers of this chemical. Sources of ignition, such as smoking and open flames, are prohibited where this chemical is used, handled, or stored in a manner that could create a potential fire or explosion hazard. Use explosion-proof electrical equipment and fittings in storage area.
Source: Hazardous Substances Data Bank (HSDB)
Incompatible materials
Explodes on mixing with carbon monoxide, hydrocarbons (e.g., butadiene, ethane, ethylene, methane, propane), fluoramines (e.g. difluoramine, trifluoramine). Mixtures with hydrogen explode with sparking or contact with platinum. Explodes on contact with mercury, potassium hydroxide, phosphorous pentachloride + chlorine. Ignites or explodes on contact with non-metals (e.g., phosphorous, sulfur, sugar). Reacts violently with /fluorine/, NHF2. Reacts with water or steam to produce toxic and corrosive fumes of /hydrochloric acid/.
Source: Hazardous Substances Data Bank (HSDB)
Planning storage for a mix of chemicals? Check Chlorine Dioxide in the storage compatibility matrix →