Sodium chlorite (NaClO
2) is a chemical compound used in the manufacturing of
paper
Paper is a thin sheet material produced by mechanically or chemically processing cellulose fibres derived from wood, Textile, rags, poaceae, grasses, Feces#Other uses, herbivore dung, or other vegetable sources in water. Once the water is dra ...
and as a
disinfectant
A disinfectant is a chemical substance or compound used to inactivate or destroy microorganisms on inert surfaces. Disinfection does not necessarily kill all microorganisms, especially resistant bacterial spores; it is less effective than ...
.
Use
The main application of sodium chlorite is the generation of
chlorine dioxide
Chlorine dioxide is a chemical compound with the formula ClO2 that exists as yellowish-green gas above 11 °C, a reddish-brown liquid between 11 °C and −59 °C, and as bright orange crystals below −59 °C. It is usually ...
for bleaching and stripping of
textile
Textile is an Hyponymy and hypernymy, umbrella term that includes various Fiber, fiber-based materials, including fibers, yarns, Staple (textiles)#Filament fiber, filaments, Thread (yarn), threads, and different types of #Fabric, fabric. ...
s,
pulp, and paper. It is also used for disinfection of 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 (such as
chloroform
Chloroform, or trichloromethane (often abbreviated as TCM), is an organochloride with the formula and a common solvent. It is a volatile, colorless, sweet-smelling, dense liquid produced on a large scale as a precursor to refrigerants and po ...
) are not produced from organic contaminants.
Chlorine dioxide
Chlorine dioxide is a chemical compound with the formula ClO2 that exists as yellowish-green gas above 11 °C, a reddish-brown liquid between 11 °C and −59 °C, and as bright orange crystals below −59 °C. It is usually ...
generated from sodium chlorite is approved by
FDA under some conditions for disinfecting water used to wash fruits, vegetables, and poultry.
Sodium chlorite, NaClO
2, sometimes in combination with
zinc chloride
Zinc chloride is an Inorganic chemistry, inorganic chemical compound with the chemical formula, formula ZnCl2·''n''H2O, with ''n'' ranging from 0 to 4.5, forming water of hydration, hydrates. Zinc chloride, anhydrous and its hydrates, are colo ...
, also finds application as a component in therapeutic rinses, mouthwashes,
toothpaste
Toothpaste is a paste or gel dentifrice that is used with a toothbrush to clean and maintain the aesthetics of Human tooth, teeth. Toothpaste is used to promote oral hygiene: it is an abrasive that aids in removing dental plaque and food from th ...
s and gels, mouth sprays, as preservative in eye drops, 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).
Chemical reagent
In
organic synthesis
Organic synthesis is a branch of chemical synthesis concerned with the construction of organic compounds. Organic compounds are molecules consisting of combinations of covalently-linked hydrogen, carbon, oxygen, and nitrogen atoms. Within the gen ...
, sodium chlorite is frequently used as a reagent in the
Pinnick oxidation for the oxidation of
aldehydes to
carboxylic acid
In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an Substituent, R-group. The general formula of a carboxylic acid is often written as or , sometimes as with R referring to an organyl ...
s. The reaction is usually performed in
monosodium phosphate buffered solution in the presence of a chlorine scavenger (usually
2-methyl-2-butene).
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.
Acidified sodium chlorite
Mixing sodium chlorite solution with a weak food-grade acid solution (commonly
citric acid
Citric acid is an organic compound with the formula . It is a Transparency and translucency, colorless Weak acid, weak organic acid. It occurs naturally in Citrus, citrus fruits. In biochemistry, it is an intermediate in the citric acid cycle, ...
), 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
The chlorite ion, or chlorine dioxide anion, is the halite (oxyanion), halite with the chemical formula of . A chlorite (compound) is a compound that contains this group, with chlorine in the oxidation state of +3. Chlorites are also known as s ...
; more acidic solutions result in a higher proportion of chlorous acid. Chlorous acid breaks down to
chlorine dioxide
Chlorine dioxide is a chemical compound with the formula ClO2 that exists as yellowish-green gas above 11 °C, a reddish-brown liquid between 11 °C and −59 °C, and as bright orange crystals below −59 °C. It is usually ...
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. ASC also is used as a teat dip for control of
mastitis in dairy cattle.
Use in public crises
The
U.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 best
biocide
A biocide is defined in the European legislation as a chemical substance or microorganism intended to destroy, deter, render harmless, or exert a controlling effect on any harmful organism. The US Environmental Protection Agency (EPA) uses a sli ...
s available for combating contaminants ranging from benign microbes and food pathogens to Category A
Bioterror agents.
In the weeks after the
9/11 attacks when
anthrax was sent in letters to public officials, hazardous materials teams used
ClO2 to decontaminate the Hart Senate Office Building, and the Brentwood Postal Facility.
In addressing the COVID-19 pandemic, the
U.S. Environmental Protection Agency has posted a list of many
disinfectant
A disinfectant is a chemical substance or compound used to inactivate or destroy microorganisms on inert surfaces. Disinfection does not necessarily kill all microorganisms, especially resistant bacterial spores; it is less effective than ...
s that meet its criteria for use in environmental measures against the causative
coronavirus
Coronaviruses are a group of related RNA viruses that cause diseases in mammals and birds. In humans and birds, they cause respiratory tract infections that can range from mild to lethal. Mild illnesses in humans include some cases of the comm ...
. Some are based on sodium chlorite that is activated into
chlorine dioxide
Chlorine dioxide is a chemical compound with the formula ClO2 that exists as yellowish-green gas above 11 °C, a reddish-brown liquid between 11 °C and −59 °C, and as bright orange crystals below −59 °C. It is usually ...
, though differing formulations are used in each product. Many other products on the EPA list contain
sodium hypochlorite, which is similar in name but should not be confused with sodium chlorite because they have very different modes of chemical action.
Safety
Sodium chlorite, like many
oxidizing 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. It also easily ignites by friction if combined with a
reducing agent
In chemistry, a reducing agent (also known as a reductant, reducer, or electron donor) is a chemical species that "donates" an electron to an (called the , , , or ).
Examples of substances that are common reducing agents include hydrogen, carbon ...
like powdered sugar, sulfur or red phosphorus.
Toxicity
Sodium chlorite is a strong
oxidant
An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or "Electron acceptor, accepts"/"receives" an electron from a (called the , , or ''electr ...
and can therefore be expected to cause clinical
symptoms similar to the well known
sodium chlorate:
methemoglobinemia
Methemoglobinemia, or methaemoglobinaemia, is a condition of elevated methemoglobin in the blood. Symptoms may include headache, dizziness, shortness of breath, nausea, poor muscle coordination, and blue-colored skin (cyanosis). Complications ma ...
,
hemolysis
Hemolysis or haemolysis (), also known by #Nomenclature, several other names, is the rupturing (lysis) of red blood cells (erythrocytes) and the release of their contents (cytoplasm) into surrounding fluid (e.g. blood plasma). Hemolysis may ...
,
kidney failure. A dose of 10-15 grams of
sodium chlorate can be lethal.
Methemoglobemia had been demonstrated in rats and cats, and recent studies by the
EMEA have confirmed that the clinical symptomatology is very similar to the one caused by
sodium chlorate in rats, mice, rabbits, and
green monkeys.
There is only one human case in the medical literature of
chlorite
The chlorite ion, or chlorine dioxide anion, is the halite (oxyanion), halite with the chemical formula of . A chlorite (compound) is a compound that contains this group, with chlorine in the oxidation state of +3. Chlorites are also known as s ...
poisoning. It seems to confirm that the
toxicity
Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacteria, bacterium, or plant, as well as the effect o ...
is equal to
sodium chlorate. From the analogy with sodium chlorate, even small amounts of about 1 gram can be expected to cause
nausea
Nausea is a diffuse sensation of unease and discomfort, sometimes perceived as an urge to vomit. It can be a debilitating symptom if prolonged and has been described as placing discomfort on the chest, abdomen, or back of the throat.
Over 30 d ...
,
vomiting
Vomiting (also known as emesis, puking and throwing up) is the forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose.
Vomiting can be the result of ailments like food poisoning, gastroenteritis, pre ...
and even life-threatening
hemolysis
Hemolysis or haemolysis (), also known by #Nomenclature, several other names, is the rupturing (lysis) of red blood cells (erythrocytes) and the release of their contents (cytoplasm) into surrounding fluid (e.g. blood plasma). Hemolysis may ...
in
glucose-6-phosphate dehydrogenase deficient persons.
The EPA has set a maximum contaminant level of 1 milligram of chlorite per liter (1 mg/L) in drinking water.
Sellers of “
Miracle Mineral Solution”, a mixture of sodium chlorite and citric acid also known as "MMS" that is promoted as a
cure-all
A panacea () is any supposed wiktionary:remedy, remedy that is claimed (for example) to cure all diseases and Immortality, prolong life indefinitely. Named after the Greek goddess of universal remedy Panacea, it was in the past sought by alchemy, ...
have been convicted, fined, or otherwise disciplined in multiple jurisdictions around the world. MMS products were variously referred to as
snake oil and
complete quackery. The U.S.
Food and Drug Administration
The United States Food and Drug Administration (FDA or US FDA) is a List of United States federal agencies, federal agency of the United States Department of Health and Human Services, Department of Health and Human Services. The FDA is respo ...
has issued multiple warnings against consuming MMS.
Manufacture
The free acid,
chlorous acid, HClO
2, is only stable at low concentrations. Since it cannot be concentrated, it is not a commercial product. However, the corresponding sodium salt, sodium chlorite, NaClO
2 is stable and inexpensive enough to be commercially available. The corresponding salts of heavy metals (
Ag+, Hg
+, Tl
+, Pb
2+, and also Cu
2+ and NH
4+) decompose explosively with heat or shock.
Sodium chlorite is derived indirectly from
sodium chlorate, NaClO
3. First, sodium chlorate is reduced to
chlorine dioxide
Chlorine dioxide is a chemical compound with the formula ClO2 that exists as yellowish-green gas above 11 °C, a reddish-brown liquid between 11 °C and −59 °C, and as bright orange crystals below −59 °C. It is usually ...
, typically in a strong acid solution using reducing agents such as
sodium sulfite,
sulfur dioxide
Sulfur dioxide (IUPAC-recommended spelling) or sulphur dioxide (traditional Commonwealth English) is the chemical compound with the formula . It is a colorless gas with a pungent smell that is responsible for the odor of burnt matches. It is r ...
, or
hydrochloric acid
Hydrochloric acid, also known as muriatic acid or spirits of salt, is an aqueous solution of hydrogen chloride (HCl). It is a colorless solution with a distinctive pungency, pungent smell. It is classified as a acid strength, strong acid. It is ...
. This intermediate is then absorbed into a solution of aqueous
sodium hydroxide
Sodium hydroxide, also known as lye and caustic soda, is an inorganic compound with the formula . It is a white solid ionic compound consisting of sodium cations and hydroxide anions .
Sodium hydroxide is a highly corrosive base (chemistry), ...
where another reducing agent converts it to sodium chlorite. Even
hydrogen peroxide
Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscosity, viscous than Properties of water, water. It is used as an oxidizer, bleaching agent, and antiseptic, usua ...
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.
General references
*"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
References
External links
International Chemical Safety Card 1045
{{DEFAULTSORT:Sodium chlorite
Sodium compounds
Chlorites
Oxidizing agents