The chlorite ion

The chlorite ion is ClO2. A chlorite (compound) is a compound that contains this group, with chlorine in oxidation state +3. Chlorites are also known as salts of chlorous acid.


Oxidation states

Chlorine can assume oxidation states of −1, +1, +3, +5, or +7 within the corresponding anions Cl, ClO, ClO2, ClO3, or ClO4, known commonly and respectively as chloride, hypochlorite, chlorite, chlorate, and perchlorate. An additional oxidation state of +4 is seen in the neutral compound chlorine dioxide ClO2, which has the same structure as chlorite ClO2 and the cation chloryl (ClO2+).

oxidation state −1 +1 +3 +5 +7
anion named chloride hypochlorite chlorite chlorate perchlorate
formula Cl- ClO ClO2 ClO3 ClO4
structure The chloride ion The hypochlorite ion The chlorite ion The chlorate ion The perchlorate ion

Some chlorite compounds


The free acid, chlorous acid, HClO2, is only stable at low concentrations. Since it cannot be concentrated, it is not a commercial product. However, the corresponding sodium salt, sodium chlorite, NaClO2 is stable and inexpensive enough to be commercially available. The corresponding salts of heavy metals (Ag+, Hg+, Tl+, Pb2+, and also Cu2+ and NH4+) decompose explosively with heat or shock.

Sodium chlorite is derived indirectly from sodium chlorate, NaClO3. First, the explosively unstable gas chlorine dioxide, ClO2 is produced by reducing sodium chlorate in a strong acid solution with a suitable reducing agent (for example, sodium chloride, sulfur dioxide, or hydrochloric acid).

H2SO4(aq) + NaClO3(s) → NaHSO4(aq) + HClO3(aq)
3HClO3(aq) → 2ClO2(g) + HClO4(aq) + H2O(l)

(Other routes for the preparation of chlorine dioxide are available depending on the initial salt).

The chlorine dioxide is then absorbed into an alkaline solution and reduced with hydrogen peroxide, H2O2 yielding sodium chlorite (NaClO2). (Sodium, Na+, spectator ions are not shown in the following equations).

2ClO2(g) + 2OH- → ClO2-(aq) + ClO3-(aq) + H2O(l)
ClO3-(aq) + H2O2(l) → ClO2-(aq) + H2O(l) + O2(g)


The main application of sodium chlorite is the generation of chlorine dioxide for bleaching and stripping of textiles, pulp, and paper. It is also used for disinfection in a few municipal water treatment plants after conversion to chlorine dioxide. An advantage in this application, as compared to the more commonly used chlorine, is that trihalomethanes are not produced from organic contaminants. In the European Union however, the use of Sodium chlorite has been phased out by 24-10-2009 for use as certain types of biocides: Product-type(PT) 2: Private area and public health area disinfectants and other biocidal products, PT 3: Veterinary hygiene biocidal products, PT 4: Food and feed area disinfectants and PT 5: Drinking water disinfectants.[1] Since September 2006, its application as molluscicide (PT 16) is forbidden as well. Sodium chlorite, NaClO2 also finds application as a component of contact lens cleaning solution under the trade name purite.


Health related information: see sodium chlorite. Sodium chlorite, like many oxidizers, should be protected from inadvertent contamination by organic materials to avoid the formation of an explosive mixture.


  1. ^ Commission Decision of 14 October 2008 concerning the non-inclusion of certain substances in Annex I, IA or IB to Directive 98/8/EC of the European Parliament and of the Council concerning the placing of biocidal products on the market (notified under document number C(2008) 5894)(Text with EEA relevance)(2008/809/EC) [1]
  • Chemistry of the Elements, N.N. Greenwood and A. Earnshaw, Pergamon Press, 1984.
  • Kirk-Othmer Concise Encyclopedia of Chemistry, Martin Grayson, Editor, John Wiley & Sons, Inc., 1985

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  • chlorite — [ klɔrit ] n. m. • 1831; de chlore ♦ Chim. Sel de l acide chloreux. Minér. Au plur. Famille de silicates naturels de fer et de magnésium, comprenant notamment la biotite. ● chlorite nom masculin Sel de l acide chloreux. ● chlorite nom féminin… …   Encyclopédie Universelle

  • Chlorite —   [k ] Plural,    1) Chemie: Chlorverbindungen.    2) Mineralogie: Sammelbezeichnung für eine zu den Tonmineralen gehörende Gruppe grünliche Schichtsilikatminerale mit sehr ähnlicher chemischer Zusammensetzung (magnesium und eisenhaltige… …   Universal-Lexikon

  • Chlorite — Chlo rite, n. [Gr. ? (sc. ?), fr. chlwro s light green.] (Min.) The name of a group of minerals, usually of a green color and micaceous to granular in structure. They are hydrous silicates of alumina, iron, and magnesia. [1913 Webster] {Chlorite… …   The Collaborative International Dictionary of English

  • Chlorite — Chlo rite, n. [Chlorous + ite.] (Chem.) Any salt of chlorous acid; as, chlorite of sodium. [1913 Webster] …   The Collaborative International Dictionary of English

  • Chlorite — Chlorite, wasserhaltige Magnesiatonerdesilikate, in denen MgO auch durch FeO, Al2O3 durch Fe2O3 vertreten sein kann. Sie sind sehr leicht spaltbar, beinahe wie Glimmer, aber die einzelnen Blättchen sind nicht so elastisch wie dieser. Die Farbe… …   Lexikon der gesamten Technik

  • Chlorite — Chlorīte, Salze der chlorigen Säure, s. Chlor …   Kleines Konversations-Lexikon

  • chlorite — chlorite1 [klôr′īt΄] n. a salt of chlorous acid containing the monovalent, negative radical ClO2 chlorite2 [klôr′īt΄] n. [L chloritis < Gr chlōritis < chlōros, pale green] any of a group of usually greenish, soft, monoclinic minerals,… …   English World dictionary

  • chlorite — chlorite1 chloritic /klaw rit ik, kloh /, adj. /klawr uyt, klohr /, n. a group of minerals, hydrous silicates of aluminum, ferrous iron, and magnesium, occurring in green platelike crystals or scales. [1595 1605; CHLOR 1 + ITE1] chlorite2 /klawr… …   Universalium

  • Chlorite — Pour les articles homonymes, voir chlorite (homonymie). L anion chlorite Les ions chlorites (ClO2 …   Wikipédia en Français

  • Chlorite — Als Chlorite bezeichnet man in der Chemie die Salze der chlorigen Säure, siehe Chlorite (Stoffgruppe) in der Mineralogie kurz eine Gruppe chemisch ähnlicher Minerale, siehe Chloritgruppe Diese Seite ist eine Begriffsklärung zur Unt …   Deutsch Wikipedia

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