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| Names | |||
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| IUPAC name Sodium chlorite | |||
| Other names Chlorous acid, sodium salt Textone | |||
| Identifiers | |||
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3D model (JSmol) | |||
| ChEBI | |||
| ChemSpider |
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| ECHA InfoCard | 100.028.942 | ||
| EC Number |
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| KEGG |
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| RTECS number |
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| UNII |
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| UN number | 1496 | ||
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| Properties | |||
| NaClO2 | |||
| Molar mass | 90.442 g/mol (anhydrous) 144.487 g/mol (trihydrate) | ||
| Appearance | white solid | ||
| Odor | odorless | ||
| Density | 2.468 g/cm3, solid | ||
| Melting point | anhydrous decomposes at 180–200 °C trihydrate decomposes at 38 °C | ||
| 75.8 g/100 mL (25 °C) 122 g/100 mL (60 °C) | |||
| Solubility | slightly soluble inmethanol,ethanol | ||
| Acidity (pKa) | 10–11 | ||
| Structure | |||
| monoclinic | |||
| Thermochemistry | |||
Std enthalpy of formation(ΔfH⦵298) | −307.0 kJ/mol | ||
| Pharmacology | |||
| D03AX11 (WHO) | |||
| Hazards | |||
| Occupational safety and health (OHS/OSH): | |||
Ingestion hazards | Category 3 | ||
Inhalation hazards | Category 2 | ||
Eye hazards | Category 1 | ||
Skin hazards | Category 1B | ||
| GHS labelling: | |||
    | |||
| Danger | |||
| H272,H301,H310,H314,H330,H400 | |||
| P210,P220,P221,P260,P262,P264,P270,P271,P273,P280,P284,P301+P330+P331,P303+P361+P353,P305+P351+P338,P310,P361,P363,P370+P378,P391,P403+P233,P405,P501 | |||
| NFPA 704 (fire diamond) | |||
| Flash point | Non-flammable | ||
| Lethal dose or concentration (LD, LC): | |||
LD50 (median dose) | 350 mg/kg (rat, oral) | ||
| Safety data sheet (SDS) | SDS | ||
| Related compounds | |||
Otheranions | Sodium chloride Sodium hypochlorite Sodium chlorate Sodium perchlorate | ||
Othercations | Potassium chlorite Barium chlorite | ||
Related compounds | Chlorine dioxide Chlorous acid | ||
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |||
Sodium chlorite (NaClO2) is a chemical compound used in the manufacturing ofpaper and as adisinfectant.
The main application of sodium chlorite is the generation ofchlorine dioxide for bleaching and stripping oftextiles,pulp, and paper. It is also used for disinfection of municipal water treatment plants after conversion to chlorine dioxide.[1]: 2 An advantage in this application, as compared to the more commonly used chlorine, is thattrihalomethanes (such aschloroform) are not produced from organic contaminants.[1]: 25, 33 Chlorine dioxide generated from sodium chlorite is approved byFDA under some conditions for disinfecting water used to wash fruits, vegetables, and poultry.[2][full citation needed][3]
Sodium chlorite, NaClO2, sometimes in combination withzinc chloride, also finds application as a component in therapeutic rinses, mouthwashes,[4][5]toothpastes and gels, mouth sprays, as preservative in eye drops,[6] and in contact lens cleaning solution under the trade name Purite.
It is also used for sanitizing air ducts and HVAC/R systems and animal containment areas (walls, floors, and other surfaces).
Inorganic synthesis, sodium chlorite is frequently used as a reagent in thePinnick oxidation for the oxidation ofaldehydes tocarboxylic acids. The reaction is usually performed inmonosodium phosphate buffered solution in the presence of a chlorine scavenger (usually2-methyl-2-butene).[7]
In 2005, sodium chlorite was used as an oxidizing agent to convert alkyl furans to the corresponding 4-oxo-2-alkenoic acids in a simple one pot synthesis.[8]
Mixing sodium chlorite solution with a weak food-grade acid solution (commonlycitric acid), both stable, produces short-lived acidified sodium chlorite (ASC) which has potent decontaminating properties. Upon mixing the main active ingredient,chlorous acid is produced in equilibrium with chlorite anion. The proportion varies with pH, temperature, and other factors, ranging from approximately 5–35%chlorous acid with 65–95%chlorite; more acidic solutions result in a higher proportion of chlorous acid. Chlorous acid breaks down tochlorine dioxide which in turn breaks down to chlorite anion and ultimately chloride anion. ASC is used for sanitation of the hard surfaces which come in contact with food and as a wash or rinse for a variety of foods including red meat, poultry, seafood, fruits and vegetables. Because the oxo-chlorine compounds are unstable when properly prepared, there should be no measurable residue on food if treated appropriately.[9][10] ASC also is used as a teat dip for control ofmastitis in dairy cattle.[11]
TheU.S. Army Natick Soldier Research, Development, and Engineering Center produced a portable "no power required" method of generating chlorine dioxide gas (ClO2), a compound described as being one of the bestbiocides available for combating contaminants ranging from benign microbes and food pathogens to Category ABioterror agents. In the weeks after the9/11 attacks whenanthrax was sent in letters to public officials, hazardous materials teams usedClO2 to decontaminate the Hart Senate Office Building, and the Brentwood Postal Facility.[12]
In addressing the COVID-19 pandemic, theU.S. Environmental Protection Agency has posted a list of manydisinfectants that meet its criteria for use in environmental measures against the causativecoronavirus.[13][14] Some are based on sodium chlorite that is activated intochlorine dioxide, though differing formulations are used in each product. Many other products on the EPA list containsodium hypochlorite, which is similar in name but should not be confused with sodium chlorite because they have very different modes of chemical action.
Sodium chlorite, like manyoxidizing agents, should be protected from inadvertent contamination by organic materials to avoid the formation of an explosive mixture. The chemical is stable in pure form and does not explode on percussive impact, unless organic contaminants are present, such as on a greasy hammer striking the chemical on an anvil.[15] It also easily ignites by friction if combined with areducing agent like powdered sugar, sulfur or red phosphorus.
Sodium chlorite is a strongoxidant and can therefore be expected to cause clinicalsymptoms similar to the well knownsodium chlorate:methemoglobinemia,hemolysis,kidney failure.[16] A dose of 10–15 grams ofsodium chlorate can be lethal.[17]Methemoglobemia had been demonstrated in rats and cats,[18] and recent studies by theEMEA have confirmed that the clinical symptomatology is very similar to the one caused bysodium chlorate in rats, mice, rabbits, andgreen monkeys.[19]
There are only a few human cases in the medical literature ofchlorite poisoning as of 2025.[20] It seems to confirm that thetoxicity is equal tosodium chlorate. From the analogy with sodium chlorate, even small amounts of about 1 gram can be expected to causenausea,vomiting and even life-threateninghemolysis inglucose-6-phosphate dehydrogenase deficient persons. Renal damage and failure is also common. Typical treatment includes methylene blue administration and hemodialysis, and a full recovery is possible with prompt and intense medical care.
The EPA has set a maximum contaminant level of 1 milligram of chlorite per liter (1 mg/L) in drinking water.[21]
Sellers of "Miracle Mineral Solution", a mixture of sodium chlorite and citric acid also known as "MMS" that is promoted as acure-all have been convicted, fined, or otherwise disciplined in multiple jurisdictions around the world. MMS products were variously referred to assnake oil andcomplete quackery. The U.S.Food and Drug Administration has issued multiple warnings against consuming MMS.[22][23][24][25][26][27][28][29][30]
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 fromsodium chlorate, NaClO3. First, sodium chlorate is reduced tochlorine dioxide, typically in a strong acid solution using reducing agents such assodium sulfite,sulfur dioxide, orhydrochloric acid. This intermediate is then absorbed into a solution of aqueoussodium hydroxide where another reducing agent converts it to sodium chlorite. Evenhydrogen peroxide can be used as the reducing agent, giving oxygen gas as its byproduct rather than other inorganic salts or materials that could contaminate the desired product.[31]
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