Chlorine dioxide

Chlorine dioxide

Names
IUPAC name Chlorine dioxide
Preferred IUPAC name Chlorine dioxide
Systematic IUPAC name Chlorine dioxide
Other names Chlorine(IV) oxide Chlorine peroxide Chloroperoxyl
Identifiers
Jmol-3D images	Image
SMILES O=Cl=O
Properties
Chemical formula	ClO2
Molar mass	67.45 g/mol
Appearance	Yellow to orange gas
Odor	Acrid
Density	2.757 g/L
Melting point	−59 °C (−74 °F; 214 K)
Boiling point	11 °C (52 °F; 284 K)
Solubility in water	8 g/L (at 20 °C)
Solubility	Soluble in alkaline and sulfuric acid solutions
Vapor pressure	>1 atm
Acidity (pKa)	3.0(5)
Thermochemistry
Std molar entropy (So298)	257.22 J·K−1·mol−1
Std enthalpy of formation (ΔfHo298)	104.60 kJ/mol
Hazards
Safety data sheet	Ecosense Company
Flash point	Non-flammable
Lethal dose or concentration (LD, LC):
LD50 (Median dose)	292 mg/kg (oral, rat)
LC50 (Median concentration)	260 ppm (rat, 2 hr)
Related compounds
Related compounds	Dichlorine heptoxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Chlorine dioxide is a chemical compound with the formula ClO₂.

Properties

Chemical

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.

Physical

Chlorine dioxide is a yellowish gas, with an acrid odor, very reactive, very soluble in water.

Availability

Chlorine dioxide is not sold and has to be made in situ.

Preparation

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

The 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

Chlorine dioxide can also be prepared also by reaction of potassium chlorate with oxalic acid:

2 KClO₃ + 2 H₂C₂O₄ → K₂C₂O₄ + 2 ClO₂ + 2 CO₂ + H₂O

2 KClO₃ + H₂C₂O₄ + 2 H₂SO₄ → 2 KHSO₄ + 2 ClO₂ + 2 CO₂ + 2 H₂O

Projects

• Bleaching of wood pulp
• Disinfection (water chlorination)
• Oxidizer
• Light sensitive reaction demonstration

Handling

Safety

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.

Storage

Chlorine dioxide cannot be safely stored. However, it can be easily made from sodium chlorite and acid.

Disposal

The gaseous form should be released in the air in remote areas. Solutions can be neutralized with a reducing agent.

References

Relevant Sciencemadness threads

• Chlorine dioxide, production and ignition of this colorful gas
• Stabilized Chlorine Dioxide
• Scared of ClO2
• ClO2 as a health product
• A word on Chlorine dioxide
• can ClO2 oxidize Cl2 ?
• Chlorine Dioxide bleaching of paper
• Acidified Sodium Chlorite (Chlorine Dioxide)