Chlorine dioxide
Identifiers
CAS number	[10049-04-4&c=0&v= [10049-04-4]]
EINECS number	233-162-8
Properties
Molecular formula	ClO2
Molar mass	67.45 g/mol
Melting point	−59°C Image File history File links Download high resolution version (1100x504, 19 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Chlorine dioxide ... Image File history File links Download high resolution version (1100x851, 170 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Chlorine dioxide ... Image File history File links Download high resolution version (1100x847, 374 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Chlorine dioxide ... CAS registry numbers are unique numerical identifiers for chemical compounds, polymers, biological sequences, mixtures and alloys. ... The EINECS number (for European Inventory of Existing Chemical Substances) is a registry number given to each chemical substance commercially available in the European Union between 1 January 1971 and 18 September 1981. ... A chemical formula is a concise way of expressing information about the atoms that constitute a particular chemical compound. ... Molar mass is the mass of one mole of a chemical element or chemical compound. ... The melting point of a crystalline solid is the temperature range at which it changes state from solid to liquid. ...
Boiling point	10°C Italic text This article is about the boiling point of liquids. ...
Solubility in other solvents	Hydrolysis
Thermochemistry
Std enthalpy of formation ΔfHo298	+104.60 kJ/mol
Standard molar entropy So298	257.22 J K−1 mol−1
Hazards
EU classification	Oxidant (O) Very toxic (T+) Dangerous for the environment (N)
R-phrases	R6, R8, R24, R36, R50
S-phrases	S1/2, S23, S26, S28, S36/37/39, S38, S45, S61
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

Chlorine dioxide is a chemical compound with the formula ClO₂. This greenish-yellow gas crystallizes as orange crystals at −59 °C. As one of several oxides of chlorine, it is a potent and useful oxidizing agent used in water treatment and in bleaching. Solubility is a chemical property referring to the ability for a given substance, the solute, to dissolve in a solvent. ... The standard enthalpy of formation or standard heat of formation of a compound is the change of enthalpy that accompanies the formation of 1 mole of a substance in its standard state from its constituent elements in their standard states (the most stable form of the element at 1 atmosphere... In chemistry, the standard molar entropy is the entropy content of one mole of substance, under conditions of standard temperature and pressure. ... Council Directive 67/548/EEC of 27 June 1967 on the approximation of laws, regulations and administrative provisions relating to the classification, packaging and labelling of dangerous substances (as amended) is the main European Union law concerning chemical safety. ... An oxidizing agent is a substance that oxidizes another substance in electrochemistry or redox chemical reactions in general. ... Toxic redirects here, but this is also the name of a song by Britney Spears; see Toxic (song) Look up toxic and toxicity in Wiktionary, the free dictionary. ... R-phrases are defined in Annex III of European Union Directive 67/548/EEC: Nature of special risks attributed to dangerous substances and preparations. ... S-phrases are defined in Annex IV of European Union Directive 67/548/EEC: Safety advice concerning dangerous substances and preparations. ... The plimsoll symbol as used in shipping In chemistry, the standard state of a material is its state at 1 bar (100 kilopascals exactly). ... A chemical compound is a chemical substance of two or more different chemically bonded chemical elements, with a fixed ratio determining the composition. ... For other uses, see Gas (disambiguation). ... An oxide is a chemical compound containing an oxygen atom and other elements. ... General Name, symbol, number chlorine, Cl, 17 Chemical series halogens Group, period, block 17, 3, p Appearance yellowish green Standard atomic weight 35. ...

Handling properties

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At concentrations greater than 15% volume in air at STP, ClO₂ explosively decomposes into chlorine and oxygen. The decomposition is initiated by light. Thus, it is never handled in concentrated form, but is almost always used as a dissolved gas in water in a concentration range of 0.5 to 10 grams per liter. Its solubility increases at lower temperatures: it is thus common to use chilled water (5 °C or 41 °F) when storing at concentrations above 3 grams per liter. In many countries, such as the USA, chlorine dioxide gas may not be transported at any concentration and is almost always produced at the application site using a chlorine dioxide generator. In some countries, chlorine dioxide solution below 3 grams per liter in concentration may be transported by land, but are relatively unstable and deteriorate quickly. Image File history File links Emblem-contradict. ... Temperature and air pressure can vary from one place to another on the Earth, and can also vary in the same place with time. ... General Name, symbol, number chlorine, Cl, 17 Chemical series halogens Group, period, block 17, 3, p Appearance yellowish green Standard atomic weight 35. ... General Name, symbol, number oxygen, O, 8 Chemical series nonmetals, chalcogens Group, period, block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Standard atomic weight 15. ... For the connotation of the term relating to chemistry, see Solvation. ...

A number of products are marketed as "stabilized chlorine dioxide" (SCD). These are not actually solutions of chlorine dioxide but solutions of buffered sodium chlorite. A weak acid can be added to SCD to "activate" it and make chlorine dioxide in-situ without a chlorine dioxide generator. The use of SCD is effective when the demand for chlorine dioxide is low and when impurities, such as small amounts of chlorine, can be tolerated. For application requiring above 5 kg day⁻¹ ClO₂, chlorine dioxide produced by a generator with either sodium chlorite or sodium chlorate is typically more economical. Sodium chlorite is a chemical compound used in the manufacture of paper. ... Sodium chlorite is a chemical compound used in the manufacture of paper. ... Sodium chlorate (NaClO3) is an oxidizing agent. ...

Uses

Chlorine dioxide is used primarily (>95%) for bleaching of wood pulp, but is also used for the bleaching of flour and for the disinfection of water. The Niagara Falls, New York water treatment plant first used chlorine dioxide for drinking water treatment in 1944 for phenol destruction. Chlorine dioxide was introduced as a drinking water disinfectant on a large scale in 1956, when Brussels, Belgium, changed from chlorine to chlorine dioxide. Its most common use in water treatment is as a pre-oxidant prior to chlorination of drinking water to reduce trihalomethanes which are a carcinogenic disinfection by-product associated with chlorination of naturally occurring organics in the raw water. Chlorine dioxide is also used in conjunction with ozone disinfection of water to reduce the formation of bromates which are regulated carcinogens. Chlorine dioxide is also superior to chlorine when operating above neutral pH, when ammonia is present and for the control of biofilms. Chlorine dioxide is used in many industrial water treatment applications as a biocide including cooling towers, process water and food processing. Chlorine dioxide is less corrosive than chlorine and superior for the control of legionella bacteria. Bleaching of wood pulp is the chemical processing carried out on various types of wood pulp to decrease the color of the pulp, so that it becomes whiter. ... This article is about the chemical whitener. ... For other uses, see Flour (disambiguation). ... This is an article about antimicrobial agents. ... For other uses, see Niagara Falls (disambiguation). ... Drinking water Mineral Water Drinking water is water that is intended to be ingested by humans. ... Phenol, also known under an older name of carbolic acid, is a colourless crystalline solid with a typical sweet tarry odor. ... For other places with the same name, see Brussels (disambiguation). ... An oxidizing agent is a substance that oxidizes another substance in electrochemistry or redox chemical reactions in general. ... Trihalomethanes (THMs) are chemical compounds in which three of the four hydrogen atoms of methane (CH4) are replaced by halogen atoms. ... It has been suggested that Ozone generator be merged into this article or section. ... The bromate ion is BrO3−. A bromate is a compound that contains this group. ... For other uses, see PH (disambiguation). ... A biocide is a chemical substance capable of killing different forms of living organisms used in fields such as medicine, agriculture, forestry, and mosquito control. ... Cooling towers are structures for cooling water or other working medium to near-ambient temperature. ... Species Legionella adelaidensis Legionella anisa Legionella beliardensis Legionella birminghamensis Legionella bozemanii Legionella brunensis Legionella busanensis Legionella cherrii Legionella cincinnatiensis Legionella donaldsonii Legionella drancourtii Legionella drozanskii Legionella erythra Legionella fairfieldensis Legionella fallonii Legionella feeleii Legionella geestiana Legionella gratiana Legionella gresilensis Legionella hackeliae Legionella israelensis Legionella jamestowniensis Legionella jordanis Legionella lansingensis Legionella...

It is more effective than chlorine against viruses, bacteria and protozoa – including the cysts of Giardia and the oocysts of Cryptosporidium. This article is about biological infectious particles. ... Phyla/Divisions Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Omnibacteria Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria (singular, bacterium) are a major group of living organisms. ... Wikisource has an original article from the 1911 Encyclopædia Britannica about: Protozoa Protozoa (in Greek proto = first and zoa = animals) are single-celled eukaryotes (organisms whose cells have nuclei) that commonly show characteristics usually associated with animals, most notably mobility and heterotrophy. ... A cyst (soft c, rhymes with list) is a closed sac having a distinct membrane and develosion on the nearby tissue. ... Binomial name (Kunstler, 1882) Giardia lamblia (synonymous with Lamblia intestinalis and Giardia duodenalis) is a flagellated protozoan parasite that colonises and reproduces in the small intestine, causing giardiasis. ... Cryptosporidium has a spore phase (oocyst) and in this state can survive for lengthy periods outside a host and also resist many common disinfectants, notably chlorine based disinfectants. ... Cryptosporidiosis is a parasitic disease affecting the intestines of mammals that is caused by Cryptosporidium, a protozoan parasite in the phylum Apicomplexa. ...

It can also be used for air disinfection, and was the principal agent used in the decontamination of buildings in the United States after the 2001 anthrax attacks. Recently, after the disaster of Hurricane Katrina in New Orleans, Louisiana and the surrounding Gulf Coast, chlorine dioxide has been used to eradicate dangerous mold from houses inundated by water from massive flooding. The 2001 anthrax attacks in the United States, also known as Amerithrax from its FBI case name, occurred over the course of several weeks beginning on September 18, 2001. ... This article is about the Atlantic hurricane of 2005. ... New Orleans is the largest city in the state of Louisiana, United States of America. ... This article is about the U.S. State. ... It has been suggested that Toxic mold be merged into this article or section. ...

Chlorine dioxide is used as an oxidant for phenol destruction in waste water streams, control of zebra mussels in water intakes and for odor control in the air scrubbers of animal byproduct (rendering) plants. Binomial name Dreissena polymorpha Pallas, 1771 The Zebra mussel (Dreissena polymorpha) is a bivalve mussel native to freshwater lakes of southeast Russia. ...

Stabilized chlorine dioxide can also be used in an oral rinse to treat oral disease and malodor.^[1]

Preparation

In the laboratory, ClO₂ is prepared by oxidation of sodium chlorite:^[2] Sodium chlorite is a chemical compound used in the manufacture of paper. ...

2NaClO₂ + Cl₂ → 2ClO₂ + 2 NaCl

ClO₂ can be produced with high efficiency by reducing sodium chlorate in a strong acid solution with a suitable reducing agent (for example, hydrogen peroxide, sulfur dioxide, or hydrochloric acid): Sodium chlorate (NaClO3) is an oxidizing agent. ... A reducing agent (also called a reductant or reducer) is the element or a compound in a redox (reduction-oxidation) reaction (see electrochemistry) that reduces another species. ... R-phrases , , , , S-phrases , , , ,, , , , Flash point Non-flammable Related Compounds Related compounds Water Ozone Hydrazine Except where noted otherwise, data are given for materials in their standard state (at 25 Â°C, 100 kPa) Infobox disclaimer and references Hydrogen peroxide (H2O2) is a very pale blue liquid which appears colourless in... Sulfur dioxide (or Sulphur dioxide) has the chemical formula SO2. ... The chemical compound hydrochloric acid is the aqueous (water-based) solution of hydrogen chloride gas (HCl). ...

2ClO₃⁻ + 2Cl⁻ + 4H⁺ → 2ClO₂ + Cl₂ + 2H₂O

Sodium chlorate reaction with hydrochloric acid: Sodium chlorate (NaClO3) is an oxidizing agent. ... The chemical compound hydrochloric acid is the aqueous (water-based) solution of hydrogen chloride gas (HCl). ...

2NaClO₃ + 4HCl → 2NaCl + 2ClO₂ + Cl₂ + 2H₂O

Over 95% of the chlorine dioxide produced in the world today is made via the sodium chlorate method for pulp bleaching.

A much smaller but important market for chlorine dioxide is for use as a disinfectant. Since 1999 a growing proportion of the chlorine dioxide made globally for water treatment and other small scale applications has been made using the chlorate, hydrogen peroxide and sulfuric acid method which can produce a chlorine free product at high efficiency.

Traditionally, chlorine dioxide for disinfection applications has been made by one of three methods using sodium chlorite or the sodium chlorite - hypochlorite method: The chlorite ion This discusses some chlorine compounds. ...

2NaClO₂ + 2HCl + NaOCl → 2ClO₂ + 3NaCl + H₂O

or the sodium chlorite - hydrochloric acid method:

5NaClO₂ + 4HCl → 5NaCl + 4ClO₂

All three sodium chlorite chemistries can produce chlorine dioxide with high chlorite conversion yield, but the chlorite-HCl method suffers from the requirement of 25% more chlorite to produce an equivalent amount of chlorine dioxide.

Catalytic chlorine dioxide generators produce extremely high conversion yields (>98.5%). With these systems sodium chlorite solution is passed through an ion exchange column. The process of ion exchange yields chlorous acid. This is then passed through a catalyst column which assists in the conversion to chlorine dioxide. The advantage of these systems is that low concentrations of chlorine dioxide can be produced directly at the point of application.

Chlorine dioxide can also be produced by electrolysis of a chlorite solution:

2NaClO₂ + 2H₂O   →   2ClO₂ + 2NaOH + H₂

High purity chlorine dioxide gas (7.7% in air or nitrogen) can be produced by the Gas:Solid method, which reacts dilute chlorine gas with solid sodium chlorite.

2NaClO₂ + Cl₂   →   2ClO₂ + 2NaCl

These processes and several slight variations have been reviewed.^[3]

References

1. ^ US patent 4689215
2. ^ Derby, R. I.; Hutchinson, W. S. "Chlorine(IV) Oxide" Inorganic Syntheses, 1953, IV, 152-158.
3. ^ White, G. C. "Handbook of Chlorination and Alternative Disinfectants", 4th Edition (Wiley, 1999).

• National Library of Medicine (US)
• WebElements
• NIST Standard Reference Database
• European Chemicals Bureau

External links

• Catalytic Chlorine Dioxide Generation and Applications
• Stabilized Chlorine Dioxide used for Oral Hygiene
• Chlorine Dioxide Applications
• National Pollutant Inventory - Chlorine dioxide
• An Interview with Chlorine Dioxide, Kevin McCue/The American Chemical Society