Potassium arsenite

{{chembox | Verifiedfields = changed | Watchedfields = changed | verifiedrevid = 426161462 | ImageFile= KAsO2.svg | ImageSize= | IUPACName= | OtherNames= |Section1={{Chembox Identifiers | index_label = meta | index1_label = ortho | CASNo1_Ref = {{cascite|changed|CAS}} | CASNo = <!--10124-50-2 varies in number of hydrogen and oxygen atoms--> <!--13464-35-2 mixture of acid and potassium--> | CASNo1 = 36267-15-9 | ChemSpiderID = 55524 | ChemSpiderID1 = 132377 | EC_number1 = 236-680-2 | UNII_Ref = {{fdacite|changed|FDA}} | UNII = HQE48MPP30 | UNII1 = K2P7R33YLY | PubChem=61616 | PubChem1 = 150167 | StdInChI=1S/AsHO2.K/c2-1-3;/h(H,2,3);/q;+1/p-1 | StdInChIKey = HEQWEGCSZXMIJQ-UHFFFAOYSA-M | SMILES=[O-][As]=O.[K+] | SMILES1 = [K+].[K+].[K+].[O-][As]([O-])[O-] | InChI1=1S/AsO3.3K/c2-1(3)4;;;/q-3;3*+1 | InChIKey1 = OZYUYLWHROWIFJ-UHFFFAOYSA-N }} |Section2={{Chembox Properties | Formula=AsKO₂ | MolarMass=146.019 g/mol | Appearance= white hygroscopic powder | Density= 8.76 g/cm³{{dubious|date=July 2025}} | MeltingPt= ~ | MeltingPtC= 300 | MeltingPt_notes = (decomposes) | BoilingPt= | Solubility= slightly soluble }} |Section3={{Chembox Hazards | MainHazards= | FlashPt= | AutoignitionPt = | LD50 = 14 mg/kg (oral, rat)<ref>[https://pubchem.ncbi.nlm.nih.gov/#tab/sidsrcname=ChemIDplus&query=10124-50-2&input_type=text nih.gov] </ref> | IDLH = Ca [5 mg/m³ (as As)]<ref name=PGCH>{{PGCH|0038}}</ref> | REL = Ca C 0.002 mg/m³ [15-minute]<ref name=PGCH/> | PEL = [1910.1018] TWA 0.010 mg/m³<ref name=PGCH/> }} }} '''Potassium arsenite''' (KAsO₂) is an inorganic compound that exists in two forms, potassium meta-arsenite (KAsO₂) and potassium ortho-arsenite (K₃AsO₃). It is composed of arsenite ions (AsO₃³⁻ or AsO₂⁻) with arsenic always existing in the +3 oxidation state.<ref name=":0">{{cite book |author=Lide, D. R. |title=CRC Handbook Chemistry & Physics 74th Edition |year=1993 |publisher=CRC-Press |isbn=0-8493-0474-1}}</ref> Like many other arsenic containing compounds, potassium arsenite is highly toxic and carcinogenic to humans. Potassium arsenite forms the basis of Fowler’s solution, which was historically used as a medicinal tonic, but was removed from market due to serious adverse effects.<ref name=":1">{{cite journal | author = Jolliffe, D. M. | title = The history of the use of arsenicals in man | journal = Journal of the Royal Society of Medicine | year = 1993 | volume = 86 | issue = 5 | pages = 287–289 | doi = 10.1177/014107689308600515 | pmc = 1294007 | pmid=8505753}}</ref><ref>{{cite journal |author1=Lander J.J. |author2=Stanley R.J. |author3=Sumner H.W. |author4=Boswell D.C. |author5=Aach R.D. | title = Angiosarcoma of the Liver associated with Fowler's Solution (Potassium Arsenite) |journal = Gastroenterology | year = 1975 | volume = 68 | issue = 6 | pages = 1582–1586 |doi=10.1016/S0016-5085(75)80148-X | pmid = 1169181 |doi-access = free }}</ref> Potassium arsenite is still, however, used as a rodenticide.<ref name=":2">Potassium Arsenite. http://nj.gov/health/eoh/rtkweb/documents/fs/1557.pdf</ref>

==Properties== Potassium arsenite is an inorganic salt that exists as an odorless white solid. It is largely soluble in water and only slightly soluble in alcohol. Solutions of potassium arsenite contain moderate concentrations of hydroxide, and are thus slightly basic.<ref name=":3">{{cite journal|last1=U.S. Dept. of Health and Human Services, Public Health Service|title=Arsenic and Inorganic Arsenic Compounds|journal=Report on Carcinogens, Thirteenth Edition|date=October 2, 2014|url=https://ntp.niehs.nih.gov/sites/default/files/ntp/roc/content/profiles/arsenic.pdf}}</ref> While potassium arsenite is noncombustible, heating it results in its decomposition and the formation of toxic fumes that include arsine, arsenic oxides, and potassium oxides. Potassium arsenite also reacts with acids to yield toxic arsine gas.<ref name=":2" />

The structure was determined by X-ray crystallography. As found for related As(III) compounds, the arsenic is pyramidal. The {{chem2|[AsO3]-}} subunits are connected by two bridging oxides.<ref>{{cite journal |last1=Emmerling |first1=Franziska |last2=Röhr |first2=Caroline |title=Die neuen Oxoarsenate(III) AAsO₂ (A = Na, K, Rb) und Cs₃As₅O₉. Darstellung, Kristallstrukturen und Raman-Spektren / The New Oxoarsenates(III) AAsO2 (A = Na, K, Rb) and Cs3As5O9. Synthesis, Crystal Structures and Raman Spectra |journal=Zeitschrift für Naturforschung B |date=2003 |volume=58 |issue=7 |pages=620–626 |doi=10.1515/znb-2003-0704}}</ref>

==Preparation== Aqueous potassium arsenite, more commonly known as Fowler’s solution, can be prepared by heating arsenic trioxide (As₂O₃) with potassium hydroxide (KOH) in the presence of water.<ref>{{cite book|last1=Caspari|first1=Charles|title=A Treatise on Pharmacy for Students and Pharmacists|date=1901|publisher=Lea Brothers and Co.|location=Philadelphia|edition=2nd|url=https://archive.org/stream/atreatiseonphar04caspgoog#page/n6/mode/2up}}</ref><ref>{{cite journal|last1=Tinwell|first1=H.|last2=Stephens|first2=S. C.|last3=Ashby|first3=J.|title=Arsenite as the probable active species in the human carcinogenicity of arsenic: mouse micronucleus assays on Na and K arsenite, orpiment, and Fowler's solution|journal=Environmental Health Perspectives|date=1991|volume=95|pages=205–210|doi=10.2307/3431125|pmc=1568403|pmid=1821373|jstor=3431125}}</ref> The reaction is shown below :As₂O₃ (aq) + 2 KOH (aq) → 2 KAsO₂ (aq) + H₂O

==Uses== In the eighteenth century English physician Thomas Fowler (1736–1801)<ref name=Doyle>{{cite journal | author = Doyle, Derek | title = Notoriety to respectability: a short history of arsenic prior to its present day use in haematology | journal = British Journal of Haematology | year = 2009 | volume = 145 | issue = 3 | pages = 309–317 | doi = 10.1111/j.1365-2141.2009.07623.x | pmid = 19298591 | s2cid = 6676910 | doi-access = free }}</ref> utilized potassium arsenite to remedy a number of conditions including anemia, rheumatism, psoriasis, eczema, dermatitis, asthma, cholera, and syphilis. Furthermore, in 1865 the potential uses of potassium arsenite expanded as Fowler’s solution was used as the first chemotherapeutic agent to treat leukemia, however the effects were only temporary. Surprisingly enough, this specific use was inspired by potassium arsenite’s role in improving digestion and producing a smoother coat in horses.<ref name=":1" /> Potassium arsenite is also a key inorganic component of certain wood preservatives, rodenticides, insecticides, and herbicides.<ref name=":3" />

==Health effects== The toxicity of potassium arsenite arises from arsenic’s high affinity for sulfhydryl groups. The formation of these arsenite-sulfur bonds impairs the functionality of certain enzymes such as glutathione reductase, glutathione peroxidases, thioredoxin reductase, and thioredoxin peroxidase. These enzymes are all closely affiliated with the defense of free radicals and the metabolism of pyruvate. Thus, exposure to potassium arsenite and other arsenite containing compounds results in the production of damaging oxygen free radicals and the arrest of cellular metabolism.<ref>{{cite journal|last1=Chen|first1=Sai-Juan|last2=Zhou|first2=Guang-Biao|last3=Zhang|first3=Xiao-Wei|last4=Mao|first4=Jian-Hua|last5=The ́|first5=Hugues de|last6=Chen|first6=Zhu|title=From an old remedy to a magic bullet: molecular mechanisms underlying the therapeutic effects of arsenic in fighting leukemia|journal=Blood|date=16 June 2011|volume=117|issue=24|pages=6425–37|doi=10.1182/blood-2010-11-283598|pmid=21422471|pmc=3123014|url=}}</ref>

Additionally, arsenite containing compounds have also been labeled carcinogens. The carcinogenicity of potassium arsenite arises from its ability to inhibit DNA repair and methylation. This impairment of the cellular machinery can lead to cancer because the cells can no longer repair or arrest mutations and a tumor results.<ref>{{cite journal|last1=Xiong|first1=Lei|last2=Wang|first2=Yinsheng|title=Quantitative Proteomic Analysis Reveals the Perturbation of Multiple Cellular Pathways in HL-60 Cells Induced by Arsenite Treatment|journal=Journal of Proteome Research|date=5 February 2010|volume=9|issue=2|pages=1129–1137|doi=10.1021/pr9011359|pmid=20050688|pmc=2819029}}</ref> All of these conditions exhibit the hazardous nature of potassium arsenite and other arsenite containing compounds. This is evidenced by a LD₅₀ of 14&nbsp;mg/kg for rats and a TDL of 74&nbsp;mg/kg for humans.<ref>{{cite web|title=Potassium arsenite|url=https://pubchem.ncbi.nlm.nih.gov/#tab/sidsrcname=ChemIDplus&query=10124-50-2&input_type=text|website=TOXNET: Toxicology Data Network|access-date=6 December 2014}}</ref>

== Notes == <references />{{Potassium compounds}}

Category:Arsenites Category:Potassium compounds Category:Withdrawn drugs