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{{Short description|Ionic compound (KCl)}} | ||
{{Distinguish|Potassium chlorate}} | |||
{{redirect|KCl|3=KCL (disambiguation)}} | |||
{{About|the salt|the use of potassium chloride as a medication|Potassium chloride (medical use)|the use of potassium in biology|Potassium in biology}} | |||
{{chembox | {{chembox | ||
| Verifiedfields = changed | | Verifiedfields = changed | ||
| Watchedfields = changed | |||
| verifiedrevid = 464362321 | |||
| verifiedrevid = 477162807 | |||
| ImageFile = Potassium chloride.jpg | | ImageFile = Potassium chloride.jpg | ||
| ImageFile1 = Potassium-chloride-3D-ionic.png | | ImageFile1 = Potassium-chloride-3D-ionic.png | ||
| OtherNames = ] |
| OtherNames = {{Unbulleted list|]|Muriate of potash}} | ||
| |
|Section1={{Chembox Identifiers | ||
| UNII_Ref = {{fdacite|correct|FDA}} | | UNII_Ref = {{fdacite|correct|FDA}} | ||
| UNII = 660YQ98I10 | | UNII = 660YQ98I10 | ||
Line 30: | Line 34: | ||
| PubChem = 4873 | | PubChem = 4873 | ||
| RTECS = TS8050000 | | RTECS = TS8050000 | ||
| ATCCode_prefix = A12 | |||
| ATCCode_suffix = BA01 | |||
| ATC_Supplemental = {{ATC|B05|XA01}} | |||
}} | }} | ||
| |
|Section2={{Chembox Properties | ||
| Formula = KCl | | Formula = KCl | ||
| MolarMass = 74. |
| MolarMass = 74.555 g·mol<sup>−1</sup> | ||
| Appearance = white crystalline solid | | Appearance = white crystalline solid | ||
| Odor = odorless | | Odor = odorless | ||
| Density = 1.984 g/cm<sup>3</sup> | | Density = 1.984 g/cm<sup>3</sup> | ||
| Solubility = |
| Solubility = 27.77 g/100mL (0 °C) <br> 33.97 g/100mL (20 °C) <br> 54.02 g/100mL (100 °C) | ||
| SolubleOther = |
| SolubleOther = Soluble in ], ]es <br> Slightly soluble in ] Insoluble in ]<ref>{{cite web | url = http://www.inchem.org/documents/pims/pharm/potasscl.htm | title = Potassium chloride (PIM 430) | at = 3.3.1 Properties of the substance | publisher = ] | access-date = 2011-01-17 | archive-date = 2010-12-04 | archive-url = https://web.archive.org/web/20101204104016/http://www.inchem.org/documents/pims/pharm/potasscl.htm | url-status = live }}</ref> | ||
| |
| Solvent1 = ethanol | ||
| Solubility1 = 0.288 g/L (25 °C)<ref>{{cite web |title=periodic-table-of-elements.org |url=https://periodic-table-of-elements.org/SOLUBILITY/potassium_chloride |access-date=4 October 2019 |format=website shows values in g/100ml |archive-date=29 October 2020 |archive-url=https://web.archive.org/web/20201029075558/https://periodic-table-of-elements.org/SOLUBILITY/potassium_chloride |url-status=dead }}</ref> | |||
| BoilingPt = 1420 °C | |||
| MeltingPtC = 770 | |||
| MeltingPt_notes = | |||
| BoilingPtC = 1420 | |||
| RefractIndex = 1.4902 (589 nm) | | RefractIndex = 1.4902 (589 nm) | ||
| pKa = ~7 | | pKa = ~7 | ||
| MagSus = −39.0·10<sup>−6</sup> cm<sup>3</sup>/mol | |||
}} | }} | ||
| |
|Section3={{Chembox Structure | ||
| CrystalStruct = ] | | CrystalStruct = ] | ||
| SpaceGroup = Fm{{overline|3}}m, No. 225 | |||
| LattConst_a = 629.2 pm<ref>{{cite book | vauthors = Sirdeshmukh DB, Sirdeshmukh L, Subhadra KG |title=Alkali Halides: A Handbook of Physical Properties |date=2001 |publisher=Springer |location=Berlin |isbn=978-3-540-42180-1}}</ref> | |||
| Coordination = Octahedral (K<sup>+</sup>)<br />Octahedral (Cl<sup>−</sup>) | |||
}} | }} | ||
| |
|Section5={{Chembox Thermochemistry | ||
| |
| DeltaHf = −436 kJ·mol<sup>−1</sup><ref name="Zumdahl-2009">{{cite book| vauthors = Zumdahl SS |title =Chemical Principles 6th Ed.| publisher = Houghton Mifflin Company| year = 2009| isbn = 978-0-618-94690-7|page=A22}}</ref> | ||
| |
| Entropy = 83 J·mol<sup>−1</sup>·K<sup>−1</sup><ref name="Zumdahl-2009"/> | ||
}} | }} | ||
| |
|Section6={{Chembox Pharmacology | ||
| ATCCode_prefix = A12 | |||
| ExternalMSDS = | |||
| ATCCode_suffix = BA01 | |||
| EUIndex = Not listed | |||
| ATC_Supplemental = {{ATC|B05|XA01}} | |||
| AdminRoutes = Oral, IV, IM | |||
| Bioavail = | |||
| Excretion = ]: 90%; Fecal: 10%<ref>{{cite web | url = https://pubchem.ncbi.nlm.nih.gov/compound/4873 | title = Compound Summary for Potassium Chloride | id = CID 4873 | work = PubChem | publisher = U.S. National Library of Medicine | access-date = 17 October 2015 | archive-date = 2 August 2023 | archive-url = https://web.archive.org/web/20230802100708/https://pubchem.ncbi.nlm.nih.gov/compound/4873 | url-status = live }}</ref> | |||
| HalfLife = | |||
| Metabolism = | |||
| ProteinBound = | |||
| Dependence_liability = | |||
}} | |||
|Section7={{Chembox Hazards | |||
| ExternalSDS = | |||
| FlashPt = Non-flammable | | FlashPt = Non-flammable | ||
| NFPA-H = 1 | | NFPA-H = 1 | ||
| NFPA-F = 0 | | NFPA-F = 0 | ||
| NFPA-R = 0 | | NFPA-R = 0 | ||
| NFPA- |
| NFPA-S = | ||
| LD50 = 2600 mg/kg (oral, rat)<ref>{{cite web|url=https://chem.nlm.nih.gov/chemidplus/rn/7447-40-7 | archive-url = https://web.archive.org/web/20150715234607/https://chem.nlm.nih.gov/chemidplus/rn/7447-40-7 | archive-date = 15 July 2015 | work = ChemIDplus | title = 7447-40-7 - WCUXLLCKKVVCTQ-UHFFFAOYSA-M - Potassium chloride | vauthors = Chambers M | publisher = U.S. National Library of Medicine |access-date=22 December 2017}}</ref> | |||
| LD50 = 2.6 g/kg (oral/rat), 0.142 g/kg (intravenous/rat)<ref>{{Cite book|title = Material Safety Data Sheet – Potassium Chloride|publisher = Sigma–Aldrich|date = July 2001}}</ref> | |||
}} | }} | ||
| |
|Section8={{Chembox Related | ||
| OtherAnions = ]<br/>]<br/>] | | OtherAnions = ]<br />]<br />] | ||
| OtherCations = ]<br/>]<br/>]<br/>] | | OtherCations = ]<br />]<br />]<br />]<br />] | ||
| |
| OtherCompounds = ]<br>]<br>]<br />] | ||
}} | }} | ||
}} | }} | ||
'''Potassium chloride''' ('''KCl''', or '''potassium salt''') is a ] ] composed of ] and ]. It is ]less and has a white or ]less ] ] appearance. The solid dissolves readily in water, and its ]s have a ]-like taste. Potassium chloride can be obtained from ancient dried lake deposits.<ref>{{Cite book| vauthors = Rayner-Canham G, Overton T |title=Descriptive inorganic chemistry|date=22 December 2013|isbn=978-1-4641-2557-7|edition=Sixth|location=New York, NY|oclc=882867766|publisher=W. H. Freeman}}</ref> KCl is used as a fertilizer,<ref>{{Cite web|url=http://extension.psu.edu/agronomy-guide/cm/sec2/sec28c|title=Potassium Fertilizers (Penn State Agronomy Guide)|website=Penn State Agronomy Guide (Penn State Extension)|access-date=2016-12-10|archive-url=https://web.archive.org/web/20161220172926/http://extension.psu.edu/agronomy-guide/cm/sec2/sec28c|archive-date=2016-12-20|url-status=dead}}</ref> in ], in scientific applications, domestic ]s (as a substitute for ] salt), and in ], where it may be known as ] additive '''E508'''. | |||
It occurs naturally as the ] ], which is named after salt's historical designations ''sal degistivum ]'' and ''sal febrifugum Sylvii'',<ref>{{Cite book |last=Watts |first=Henry |url=https://books.google.com/books?id=d-bkUHqUZ5AC&pg=PA147 |title=A Dictionary of Chemistry and the Allied Branches of Other Sciences |date=1883 |publisher=Longmans, Green, and Company |language=en}}</ref> and in combination with ] as ].<ref name=Ullmann/> | |||
The ] '''potassium chloride''' (KCl) is a ] ] ] composed of ] and ]. In its pure state, it is ]less and has a white or ]less ] ] appearance, with a ] that cleaves easily in three directions. Potassium chloride crystals are ]. Potassium chloride was historically known as "] of potash," this name is occasionally still encountered in association with its use as a ]. ] varies in color from pink or red to white depending on the ] and recovery process used. White potash, sometimes referred to as soluble potash, is usually higher in analysis and is used primarily for making liquid starter ]s. KCl is used in ], scientific applications, and ]. It occurs naturally as the ] ] and in combination with ] as ]. | |||
==Uses== | |||
===Fertilizer=== | |||
]The majority of the potassium chloride produced is used for making ], called ], since the growth of many ]s is limited by potassium availability.<ref>{{cite book|isbn=978-93-5606-271-9|title=The Nature and Properties of Soils|first1=Ray|last1=Weil|first2=Nyle|last2=Brady|year=2022|publisher=Pearson Education}}</ref><ref>{{cite journal|doi=10.1051/agro/2009023 |title=Mineral sources of potassium for plant nutrition. A review |date=2010 |last1=Manning |first1=David A.C. |journal=Agronomy for Sustainable Development |volume=30 |issue=2 |pages=281–294 |bibcode=2010AgSD...30..281M }}</ref> The term "potash" refers to various mined and manufactured salts that contain potassium in water-soluble form. Potassium chloride sold as fertilizer is known as "muriate of potash"—it is the common name for potassium chloride ({{chem|K|Cl}}) used in agriculture.<ref>{{cite book|isbn=978-93-325-7034-4 |title=Soil Fertility and Fertilizers: An Introduction to Nutrient Management |last1=Havlin |first1=John L. |last2=Tisdale |first2=Samuel L. |last3=Nelson |first3=Werner L. |last4=Beaton |first4=James D. |date=2016 |publisher=Pearson }}</ref><ref>{{cite book|url=http://potassium.ipni.net/ipniweb/region/potassium.nsf/0/58AFA539CC03133085258178006F5140/$FILE/NSS-03%20PotassiumChloride.pdf|title=Nutrient Source Specifics: Potassium Chloride. Ref. No. 17 #13075|publisher=International Plant Nutrition Institute (IPNI)|access-date=2024-11-24|archive-date=2024-04-14|archive-url=https://web.archive.org/web/20240414005645/http://potassium.ipni.net/ipniweb/region/potassium.nsf/0/58AFA539CC03133085258178006F5140/%24FILE/NSS-03%20PotassiumChloride.pdf|url-status=live}}</ref><ref>{{cite book |last1=Havlin |first1=John L. |last2=Tisdale |first2=Samuel L. |last3=Nelson |first3=Werner L. |last4=Beaton |first4=James D. |title=Soil Fertility and Fertilizers |edition=8th |publisher=Pearson Education |year=2014 |isbn=978-0-13-503373-9 |pages=186–188 |chapter=Potassium |url=https://www.pearson.com/us/higher-education/program/Havlin-Soil-Fertility-and-Fertilizers-8th-Edition/PGM334285.html}}</ref><ref name="Manning-2010">{{cite journal |last1=Manning |first1=David A. C. |title=Mineral sources of potassium for plant nutrition. A review |journal=Agronomy for Sustainable Development |volume=30 |issue=2 |year=2010 |pages=281–294 |doi=10.1051/agro/2009023 |bibcode=2010AgSD...30..281M |url=https://link.springer.com/article/10.1051/agro/2009023 |access-date=2024-11-24 |archive-date=2024-02-28 |archive-url=https://web.archive.org/web/20240228002627/https://link.springer.com/article/10.1051/agro/2009023 |url-status=live |url-access=subscription }}</ref> The vast majority of potash fertilizer worldwide is sold as muriate of potash.<ref>{{cite book|url=https://pubs.usgs.gov/periodicals/mcs2024/mcs2024-potash.pdf|series=United States Geological Survey (USGS)|title=Mineral Commodity Summaries: Potash|publisher=U.S. Department of the Interior.|access-date=2024-11-24|archive-date=2024-11-12|archive-url=https://web.archive.org/web/20241112131501/https://pubs.usgs.gov/periodicals/mcs2024/mcs2024-potash.pdf|url-status=live}}</ref><ref>{{cite book|url=https://openknowledge.fao.org/server/api/core/bitstreams/b66da618-027b-4124-a5c7-f870cd671484/content|title=FAO Fertilizer and Plant Nutrition Bulletin.|chapter=Fertilizer Use by Crop|publisher=Food and Agriculture Organization of the United Nations|access-date=2024-11-24|archive-date=2024-09-02|archive-url=https://web.archive.org/web/20240902213631/https://openknowledge.fao.org/server/api/core/bitstreams/b66da618-027b-4124-a5c7-f870cd671484/content|url-status=live}}</ref> The dominance of muriate of potash in the fertilizer market is due to its high potassium content (approximately 60% {{chem|K|2|O}} equivalent) and relative affordability compared to other potassium sources like sulfate of potash (]).<ref name="Manning-2010"/><ref>{{cite book |last1=Roy |first1=Ram N. |last2=Finck |first2=Arnold |last3=Blair |first3=Graeme J. |last4=Tandon |first4=H.L.S. |title=Plant Nutrition for Food Security: A Guide for Integrated Nutrient Management |series=FAO Fertilizer and Plant Nutrition Bulletin 16 |publisher=Food and Agriculture Organization of the United Nations |year=2006 |isbn=92-5-105490-8|pages=141–142 |url=http://www.fao.org/3/a0443e/a0443e00.htm |access-date=2024-11-24 |archive-date=2023-01-02 |archive-url=https://web.archive.org/web/20230102211021/https://www.fao.org/3/a0443e/a0443e00.htm |url-status=live }}</ref> Potassium is one of the three primary macronutrients essential for plant growth, alongside nitrogen and phosphorus. Potassium plays a vital role in various plant physiological processes, including enzyme activation, photosynthesis, protein synthesis, and water regulation.<ref>{{cite book |last1=Brady |first1=Nyle C. |last2=Weil |first2=Ray R. |title=The Nature and Properties of Soils |edition=15th |publisher=Pearson Education |year=2016 |isbn=978-0-13-325448-8 |pages=594–595 |chapter=Plant Nutrients and Nutrient Uptake |url=https://www.pearson.com/us/higher-education/program/Brady-Nature-and-Properties-of-Soils-The-15th-Edition/PGM203380.html}}</ref><ref>{{cite journal |last1=Römheld |first1=Volker |last2=Kirkby |first2=Ernest A. |title=Research on potassium in agriculture: needs and prospects |journal=Plant and Soil |volume=335 |issue=1 |year=2010 |pages=155–180 |doi=10.1007/s11104-010-0520-1 |bibcode=2010PlSoi.335..155R |url=https://link.springer.com/article/10.1007/s11104-010-0520-1 |access-date=2024-11-24 |archive-date=2024-07-09 |archive-url=https://web.archive.org/web/20240709175824/https://link.springer.com/article/10.1007/s11104-010-0520-1 |url-status=live |url-access=subscription }}</ref> For watering plants, a moderate concentration of potassium chloride (KCl) is used to avoid potential toxicity: 6 mM (millimolar) is generally effective and safe for most plants, that is approximately {{convert|0.4|g}} per liter of water.<ref>{{cite journal|doi=10.3389/fpls.2020.00904|doi-access=free |title=Effects of Potassium Levels on Plant Growth, Accumulation and Distribution of Carbon, and Nitrate Metabolism in Apple Dwarf Rootstock Seedlings |date=2020 |last1=Xu |first1=Xinxiang |last2=Du |first2=Xin |last3=Wang |first3=Fen |last4=Sha |first4=Jianchuan |last5=Chen |first5=Qian |last6=Tian |first6=Ge |last7=Zhu |first7=Zhanling |last8=Ge |first8=Shunfeng |last9=Jiang |first9=Yuanmao |journal=Frontiers in Plant Science |volume=11 |page=904 |pmid=32655607 |pmc=7325393 }}</ref><ref>{{cite journal|doi=10.1371/journal.pone.0066259|doi-access=free |title=Optimisation of Potassium Chloride Nutrition for Proper Growth, Physiological Development and Bioactive Component Production in Prunella vulgaris L |date=2013 |last1=Chen |first1=Yuhang |last2=Yu |first2=Manman |last3=Zhu |first3=Zaibiao |last4=Zhang |first4=Lixia |last5=Guo |first5=Qiaosheng |journal=PLOS ONE |volume=8 |issue=7 |pages=e66259 |pmid=23874390 |pmc=3706589 |bibcode=2013PLoSO...866259C }}</ref> | |||
===Medical use=== | |||
{{Main|Potassium chloride (medical use)}} | |||
Potassium is vital in the ], and potassium chloride by mouth is the standard means to treat ], although it can also be given intravenously. It is on the ].<ref name="WHO21st">{{cite book | vauthors = ((World Health Organization)) | title = World Health Organization model list of essential medicines: 21st list 2019 | year = 2019 | hdl = 10665/325771 | author-link = World Health Organization | publisher = World Health Organization | location = Geneva | id = WHO/MVP/EMP/IAU/2019.06. License: CC BY-NC-SA 3.0 IGO | hdl-access=free }}</ref> It is also an ingredient in ] (ORT)/solution (ORS) to reduce hypokalemia caused by diarrhoea.<ref name="who-new-ors-2006">{{cite book |last1=World Health Organization |url=https://apps.who.int/iris/bitstream/handle/10665/69227/WHO_FCH_CAH_06.1.pdf |title=Oral rehydration salts: production of the new ORS |last2=Unicef |publisher= |year=2006 |series=WHO/FCH/CAH/06.1 |hdl=10665/69227 |id= |author-link=World Health Organization |author-link2=UNICEF |access-date=2024-11-14 |archive-date=2023-06-03 |archive-url=https://web.archive.org/web/20230603021940/https://apps.who.int/iris/bitstream/handle/10665/69227/WHO_FCH_CAH_06.1.pdf |url-status=live }}</ref> This is another medicine on the ].<ref name="WHO21st"/> | |||
Potassium chloride contains 52% of elemental potassium by mass.<ref>{{cite journal|doi=10.1088/1755-1315/648/1/012185 |title=Applications of guano and K<sub>2</sub>CO<sub>3</sub> on soil potential-P, potential-K on Andisols |date=2021 |last1=Zakiah |first1=K. |last2=Maulana |first2=M. R. |last3=Widowati |first3=L. R. |last4=Mutakin |first4=J. |journal=IOP Conference Series: Earth and Environmental Science |volume=648 |issue=1 |page=012185 |bibcode=2021E&ES..648a2185Z |doi-access=free }}</ref> | |||
Overdose causes ] which can disrupt cell signaling to the extent that the heart will stop, reversibly in the case of some ].<ref name="pmid29679302">{{cite journal |vauthors=Hoppe LK, Muhlack DC, Koenig W, Carr PR, Brenner H, Schöttker B |title=Association of Abnormal Serum Potassium Levels with Arrhythmias and Cardiovascular Mortality: a Systematic Review and Meta-Analysis of Observational Studies |journal=Cardiovasc Drugs Ther |volume=32 |issue=2 |pages=197–212 |date=20 April 2018 |pmid=29679302 |doi=10.1007/s10557-018-6783-0}}</ref><ref name="pmid37046560">{{cite journal |vauthors=Simon G |title=Detection of Fatal Potassium Overdose: A Case Report and Review of the Literature |journal=Diagnostics (Basel) |volume=13 |issue=7 |date=4 April 2023 |page=1339 |pmid=37046560 |pmc=10093193 |doi=10.3390/diagnostics13071339|doi-access=free }}</ref><ref name="pmid38195532">{{cite journal |vauthors=Fan Y, Wu M, Li X, Zhao J, Shi J, Ding L, Jiang H, Li Z, Zhang W, Ma T, Wang D, Ma L |title=Potassium levels and the risk of all-cause and cardiovascular mortality among patients with cardiovascular diseases: a meta-analysis of cohort studies |journal=Nutr J |volume=23 |issue=1 |pages=8 |date=10 January 2024 |pmid=38195532 |pmc=10777575 |doi=10.1186/s12937-023-00888-z|doi-access=free }}</ref> | |||
===Culinary use=== | |||
Potassium chloride can be used as a ] for ], but due to its weak, bitter, unsalty ], it is often mixed with ordinary table salt (sodium chloride) to improve the ], to form ]. The addition of 1 ppm of ] considerably reduces this bitterness.<ref>{{cite book | vauthors = Lorient D, Linden G |title=New ingredients in food processing: biochemistry and agriculture |url=https://archive.org/details/newingredientsfo00lind |url-access=limited |publisher=CRC Press |location=Boca Raton |year=1999 |page= |isbn=978-1-85573-443-2 |quote=... in dietary food containing potassium chloride, thaumatin added in the ratio of 1 ppm considerably reduces the sensation of bitterness. ... }}</ref> Complaints of bitterness or a chemical or metallic taste are also reported with potassium chloride used in food.<ref>{{cite journal | vauthors = Sinopoli DA, Lawless HT | title = Taste properties of potassium chloride alone and in mixtures with sodium chloride using a check-all-that-apply method | journal = Journal of Food Science | volume = 77 | issue = 9 | pages = S319–S322 | date = September 2012 | pmid = 22901084 | doi = 10.1111/j.1750-3841.2012.02862.x }}</ref> | |||
===Execution=== | |||
In the United States, potassium chloride is used as the final drug in the three-injection sequence of ] as a form of ]. It induces ], ultimately killing the inmate.<ref>{{Cite web |title=Overview of Lethal Injection Protocols |url=https://deathpenaltyinfo.org/executions/lethal-injection/overview-of-lethal-injection-protocols |access-date=2024-02-28 |website=Death Penalty Information Center |language=en-US |archive-date=2024-08-06 |archive-url=https://web.archive.org/web/20240806224149/https://deathpenaltyinfo.org/executions/lethal-injection/overview-of-lethal-injection-protocols |url-status=live }}</ref> | |||
===Industrial=== | |||
{{More citations needed section|date=September 2022}} | |||
As a chemical ], the salt is used for the ] of ] and ] metal. It is also used in medicine, ]s, ] applications, ], ]s, and as a sodium-free substitute for ] for people concerned about the health effects of sodium.{{citation needed|date=November 2024}} | |||
It is used as a supplement in animal feed to boost the potassium level in the feed. As an added benefit, it is known to increase milk production.{{citation needed|date=November 2024}} | |||
It is sometimes used in solution as a ] fluid in ] and ] operations, as well as being an alternative to ] in household ] units.{{citation needed|date=November 2024}} | |||
Glass manufacturers use granular potash as a ], lowering the temperature at which a mixture melts. Because potash imparts excellent clarity to glass, it is commonly used in eyeglasses, glassware, televisions, and computer monitors.{{citation needed|date=November 2024}} | |||
Because natural potassium contains a tiny amount of the isotope ], potassium chloride is used as a ] source to calibrate ]. It also emits a relatively low level of 511 keV gamma rays from positron annihilation, which can be used to calibrate medical scanners.{{citation needed|date=November 2024}} | |||
Potassium chloride is used in some ] products designed to be safer for pets and plants, though these are inferior in melting quality to ]. It is also used in various brands of ].{{citation needed|date=November 2024}} | |||
Potassium chloride was once used as a ], and in portable and wheeled ]s. Known as Super-K dry chemical, it was more effective than ]-based dry chemicals and was compatible with ]. This agent fell out of favor with the introduction of ] (]) dry chemical in the late 1960s, which was much less ], as well as more effective. It is rated for B and C fires.{{citation needed|date=November 2024}} | |||
Along with ] and ], potassium chloride is used as a ] for the ] of ].{{citation needed|date=November 2024}} | |||
Potassium chloride is also an optical crystal with a wide transmission range from 210 nm to 20 μm. While cheap, KCl crystals are ]. This limits its application to protected environments or short-term uses such as prototyping. Exposed to free air, KCl optics will "rot". Whereas KCl components were formerly used for ] ], they have been entirely replaced by much tougher crystals such as ].{{citation needed|date=November 2024}} | |||
Potassium chloride is used as a ] with designation P10 in ]s, e.g. in the ].{{citation needed|date=November 2024}} | |||
==Toxicity== | |||
The typical amounts of potassium chloride found in the diet appear to be generally safe.<ref>{{cite web | author = Center for Food Safety and Applied Nutrition|title=GRAS Substances (SCOGS) Database - Select Committee on GRAS Substances (SCOGS) Opinion: Potassium chloride|url=https://www.fda.gov/Food/IngredientsPackagingLabeling/GRAS/SCOGS/ucm261000.htm|archive-url=https://wayback.archive-it.org/7993/20171031064321/https://www.fda.gov/Food/IngredientsPackagingLabeling/GRAS/SCOGS/ucm261000.htm|url-status=dead|archive-date=31 October 2017|website=www.fda.gov|access-date=21 July 2019|language=en}}</ref> In larger quantities, however, potassium chloride is toxic. The {{LD50}} of orally ingested potassium chloride is approximately 2.5 g/kg, or {{convert|190|g|oz}} for a body mass of {{convert|75|kg|lb}}. In comparison, the {{LD50}} of ] (table salt) is 3.75 g/kg. | |||
Intravenously, the {{LD50}} of potassium chloride is far smaller, at about 57.2 mg/kg to 66.7 mg/kg; this is found by dividing the lethal concentration of positive potassium ions (about 30 to 35 mg/kg)<ref>{{cite journal | vauthors = Bhatkhande CY, Joglekar VD | title = Fatal poisoning by potassium in human and rabbit | journal = Forensic Science | volume = 9 | issue = 1 | pages = 33–36 | date = 1977-01-01 | pmid = 838413 | doi = 10.1016/0300-9432(77)90062-0 }}</ref> by the proportion by mass of potassium ions in potassium chloride (about 0.52445 mg K<sup>+</sup>/mg KCl).<ref>{{Cite web|url=https://www.convertunits.com/molarmass/KCl|title=Molecular weight of KCl|website=www.convertunits.com|access-date=2018-11-04|archive-date=2018-11-05|archive-url=https://web.archive.org/web/20181105012256/https://www.convertunits.com/molarmass/KCl|url-status=live}}</ref> | |||
==Chemical properties== | ==Chemical properties== | ||
In ] and ], it is a very commonly used standard, for example as a ] standard solution in measuring ] of (ionic) solutions, since carefully prepared KCl solutions have well-reproducible and well-repeatable measurable properties. | |||
===Solubility=== | |||
<div style="float:left; margin:5px;"> | |||
KCl is soluble in a variety of polar solvents. | |||
{| class="toccolours" border="1" style="margin: 1em; border-collapse: collapse;" | |||
{| class="wikitable" style="margin: 1em;" | |||
! {{chembox header}}|Solubility of KCl in various solvents<br/ >(g KCl / 1 kg of solvent at 25°C)<ref>{{cite book|author=Burgess, J.|title=Metal Ions in Solution|publisher=Ellis Horwood|place=New York|year=1978|isbn=0-85312-027-7}}</ref> | |||
|+ Solubility<ref>{{cite book| vauthors = Burgess J |title=Metal Ions in Solution|publisher=Ellis Horwood|place=New York|year=1978|isbn=978-0-85312-027-8}}{{page needed|date=July 2015}}</ref> | |||
! Solvent !! Solubility<br>(g/kg of solvent at 25 °C) | |||
|- | |||
| ] || 360 | |||
|- | |- | ||
| ] || 360 | |||
|- | |||
| ] || 0.4 | | ] || 0.4 | ||
|- | |- | ||
Line 87: | Line 155: | ||
|- | |- | ||
| ] || 5.3 | | ] || 5.3 | ||
|- | |||
| ] || 0.37 | |||
|- | |- | ||
| ] || 192 | | ] || 192 | ||
Line 102: | Line 172: | ||
| ] || 0.17–0.5 | | ] || 0.17–0.5 | ||
|} | |} | ||
</div> | |||
Solutions of KCl are common standards, for example for ] of the ] of (ionic) solutions, since KCl solutions are stable, allowing for reproducible measurements. In ], it is essentially fully ionized into solvated {{chem2|K+}} and {{chem2|Cl-}} ions. | |||
Potassium chloride can react as a source of ] ]. As with any other ] ionic chloride, it will precipitate insoluble chloride ]s when added to a ] of an appropriate metal ion: | |||
===Redox and the conversion to potassium metal=== | |||
:KCl(]) + ](aq) → ](]) + KNO<sub>3</sub>(aq) | |||
Although potassium is more ] than ], KCl can be reduced to the metal by reaction with metallic sodium at 850 °C because the more volatile potassium can be removed by distillation (see ]): | |||
:<chem>KCl_{(l)}{} + Na_{(l)} <=> NaCl_{(l)}{} + K_{(g)}</chem> | |||
This method is the main method for producing metallic potassium. ] (used for sodium) fails because of the high solubility of potassium in molten KCl.<ref name=Ullmann>{{cite book | vauthors = Burkhardt ER |chapter=Potassium and Potassium Alloys |year=2006 |title=Ullmann's Encyclopedia of Industrial Chemistry |doi=10.1002/14356007.a22_031.pub2|isbn=978-3-527-30673-2 }}</ref> | |||
Although potassium is more ] than ], KCl can be reduced to the metal by reaction with metallic sodium at 850°C because the potassium is removed by distillation (see ]): | |||
{{clear}} | |||
===Other potassium chloride stoichiometries=== | |||
:KCl(l) + Na(l) ⇌ NaCl(l) + K(g) | |||
Potassium chlorides with formulas other than KCl have been predicted to become stable under pressures of 20 GPa or more.<ref>{{Cite journal|last1=Zhang|first1=Weiwei|last2=Oganov|first2=Artem R.|last3=Zhu|first3=Qiang|last4=Lobanov|first4=Sergey S.|last5=Stavrou|first5=Elissaios|last6=Goncharov|first6=Alexander F.|title=Stability of numerous novel potassium chlorides at high pressure|journal=Sci Rep|volume=6|page=26265|date=23 May 2016|doi=10.1038/srep26265|pmid=27211847 |pmc=4876327|bibcode=2016NatSR...626265Z }}</ref> Among these, two phases of KCl<sub>3</sub> were synthesized and characterized. At 20-40 GPa, a trigonal structure containing K<sup>+</sup> and Cl<sub>3</sub><sup>−</sup> is obtained; above 40 GPa this gives way to a phase isostructural with the intermetallic compound Cr<sub>3</sub>Si.{{cn|date=December 2024}} | |||
==Physical properties== | |||
This method is the main method for producing metallic potassium. ] (used for sodium) fails because of the high solubility of potassium in molten KCl. | |||
] potassium chloride!", an ad above a highway in a banana-growing district of ], ], China]] | |||
Under ambient conditions, the crystal structure of potassium chloride is like that of NaCl. It adopts a face-centered cubic structure known as the B1 phase with a ] constant of roughly 6.3 Å. Crystals cleave easily in three directions. Other polymorphic and hydrated phases are adopted at high pressures.<ref>{{cite journal | vauthors = Yamashita K, Komatsu K, Kagi H | title = Crystal structure of potassium chloride monohydrate: water intercalation into the B1 structure of KCl under high pressure | journal = Acta Crystallographica Section C | volume = 78 | issue = Pt 12 | pages = 749–754 | date = December 2022 | pmid = 36468558 | pmc = 9720884 | doi = 10.1107/S2053229622011135 | bibcode = 2022AcCrC..78..749Y }}</ref> | |||
Some other properties are | |||
As with other compounds containing potassium, KCl in powdered form gives a lilac ] result. | |||
* Transmission range: 210 nm to 20 μm | |||
* ] = 92% at 450 nm and rises linearly to 94% at 16 μm | |||
* Refractive index = 1.456 at 10 μm | |||
* Reflection loss = 6.8% at 10 μm (two surfaces) | |||
* d''N''/d''T'' (expansion coefficient)= −33.2×10<sup>−6</sup>/°C | |||
* d''L''/d''T'' (refractive index gradient)= 40×10<sup>−6</sup>/°C | |||
* Thermal conductivity = 0.036 W/(cm·K) | |||
* ] (Newman and Novak): 4 GW/cm<sup>2</sup> or 2 J/cm<sup>2</sup> (0.5 or 1 ns pulse rate); 4.2 J/cm<sup>2</sup> (1.7 ns pulse rate Kovalev and Faizullov) | |||
As with other compounds containing potassium, KCl in powdered form gives a lilac ]. | |||
==Physical properties== | |||
Potassium chloride has a crystalline structure like many other salts. Its structure is face-centered cubic. Its ] constant is roughly 630 ]s. Some other properties are | |||
*Transmission range: 210 nm to 20 µm | |||
*] = 92% at 450 nm and rises linearly to 94% at 16 µm | |||
*Refractive index = 1.456 at 10 µm | |||
*Reflection Loss = 6.8% at 10 µm (two surfaces) | |||
*d''N''/d''T'' (expansion coefficient)= −33.2×10<sup>−6</sup>/°C | |||
*d''L''/d''T'' (refractive index gradient)= 40×10<sup>−6</sup>/°C | |||
*Thermal conductivity = 0.036 W/(cm·K) | |||
*Damage threshold (Newman & Novak): 4 GW/cm<sup>2</sup> or 2 J/cm<sup>2</sup> (0.5 or 1 ns pulse rate); 4.2 J/cm<sup>2</sup> (1.7 ns pulse rate Kovalev & Faizullov) | |||
==Production== | ==Production== | ||
] | ] | ||
] | ] | ||
Potassium chloride |
Potassium chloride is extracted from minerals ], ], and ]. It is also extracted from ] and can be manufactured by crystallization from solution, ] or ] separation from suitable minerals. It is a by-product of the production of ] from ] and ]. | ||
Most potassium chloride is produced as agricultural and industrial-grade potash in ], Russia, and Belarus. Saskatchewan alone accounted for over 25% of the world's potash production in 2017.<ref>{{Cite web | publisher = U.S. Geological Survey | title = Mineral Commodity Summaries | date = January 2018 |url=https://minerals.usgs.gov/minerals/pubs/commodity/potash/mcs-2018-potas.pdf | archive-url = https://web.archive.org/web/20190110210319/https://minerals.usgs.gov/minerals/pubs/commodity/potash/mcs-2018-potas.pdf | archive-date = 10 January 2019 }}</ref> | |||
==Uses== | |||
The majority of the potassium chloride produced is used for making ], since the growth of many ]s is limited by their potassium intake. As a chemical ], it is used for the ] of ] and ] metal. It is also used in medicine, ]s, ] applications, ], and as a sodium-free substitute for ] (sodium chloride). | |||
===Laboratory methods=== | |||
It is sometimes used in ] as a ] fluid in ] and ] operations, as well as being an alternative to ] in household ] units. KCl is useful as a ] source for ] of ], because natural potassium contains 0.0118% of the ] <sup>40</sup>K. One ] of KCl yields 16350 ]s of ] consisting of 89.28% beta and 10.72% ] with 1.46083 MeV. Potassium chloride is used in some ] products that are designed to be safer for pets and plants, though these are inferior in melting quality to ] (lowest usable temperature {{convert|0|F|C}} v. {{convert|-25|F|C}}). It is also used in various brands of ], as well as in bulk quantities for ] ] purposes. | |||
Potassium chloride is inexpensively available and is rarely prepared intentionally in the laboratory. It can be generated by treating ] (or other potassium bases) with ]: | |||
:<chem>KOH + HCl -> KCl + H2O</chem> | |||
This conversion is an ]. The resulting salt can then be purified by recrystallization. Another method would be to allow potassium to burn in the presence of chlorine gas, also a very exothermic reaction: | |||
Potassium chloride was once used as a ], used in portable and wheeled ]s. Known as Super-K dry chemical, it was more effective than ]-based dry chemicals and was compatible with ]. This agent fell out of favor with the introduction of ] (]) dry chemical in the late 1960s, which was much less ] and more effective. It is rated for B and C fires. | |||
:<chem>2 K + Cl2 -> 2 KCl</chem> | |||
== References == | |||
Along with ] and ], potassium chloride is used as a ] for the ] of ]. | |||
{{Reflist}} | |||
== Further reading == | |||
Potassium chloride is also an optical crystal with a wide transmission range from 210 nm to 20 µm. While cheap, KCl crystal is ]. This limits its application to protected environments or short term uses such as prototyping. Exposed to free air, KCl optics will "rot". Whereas KCl components were formerly used for ], it has been entirely replaced by much tougher crystals like ]. | |||
{{refbegin}} | |||
* {{RubberBible86th|name-list-style=vanc}} <!--Specify page. The citation wasn't the 71st ed. Does the 86th ed. contain the appropriate verification --> | |||
* {{Greenwood&Earnshaw1st|name-list-style=vanc}} <!--Specify page --> | |||
{{refend}} | |||
== External links == | |||
Potassium chloride has also been used to create ] which employ ] ]s,<ref>{{US patent|3874504}}</ref> but these are no longer being created due to cheaper and more efficient methods, such as the oxidation of metals ('Hot Hands', one time use products) or the ] of ] (multiple use products). | |||
Potassium chloride is used as a ] with designation '''P10''' in ]s, e.g. in the ]. | |||
==Biological and medical properties== | |||
Potassium is vital in the ], and oral potassium chloride is the common means to replenish it, although it can also be diluted and given ]. It can be used as a ] for ], but due to its weak, bitter, unsalty ], it is usually mixed with ordinary salt (sodium chloride) for this purpose to improve the ]. The addition of 1 ppm of ] considerably reduces this bitterness.<ref>{{cite book |author=Lorient, Denis; Linden, G. |title=New ingredients in food processing: biochemistry and agriculture |publisher=CRC Press |location=Boca Raton |year=1999 |page=357 |isbn=1-85573-443-5 |quote=... in dietary food containing potassium chloride, thaumatin added in the ratio of 1 ppm considerably reduces the sensation of bitterness. ... |accessdate=2010 Aug 7}}</ref> Medically, it is used in the treatment of ] and associated conditions, for ] ]ing, and as an ] replenisher.<ref>. Emedicine.medscape.com. Retrieved on 2012-02-16.</ref> Brand names include K-Dur, Klor-Con, Micro-K, Slow-K and Kaon Cl. Side effects can include ] discomfort including ] and ], ] and ] of the digestive tract. ]s cause ], which can lead to ], ] conduction blocks, ], ], and ].<ref>. Emedicine.medscape.com. Retrieved on 2012-02-16.</ref> Prescription ] (the potassium naturally found in fruits and vegetables) can be prescribed as an alternative to potassium chloride. Slow-K is a 1950s development where the medicine is formulated to enter the bloodstream at delayed intervals. It was first only prescribed to British military forces to balance their diets while serving in Korea.<ref>{{cite journal|doi=10.1161/01.HYP.0000158264.36590.19|title=Effect of Short-Term Supplementation of Potassium Chloride and Potassium Citrate on Blood Pressure in Hypertensives|year=2005|last1=He|first1=F. J.|journal=Hypertension|volume=45|pages=571–4|pmid=15723964|last2=Markandu|first2=ND|last3=Coltart|first3=R|last4=Barron|first4=J|last5=MacGregor|first5=GA|issue=4}}</ref> | |||
Some ] procedures cannot be carried out on the beating heart. For these procedures, the surgical team will bypass the heart with a ] and inject potassium chloride into the heart muscle to stop the heartbeat. | |||
The lethal effects of potassium chloride overdoses have led to its use in ], | |||
as the third of a three-drug combination. Additionally, KCl is used (albeit rarely) in fetal intracardiac injections in second- and third-trimester ]s.<ref>{{cite journal |author=Stubblefield PG |title=Methods for induced abortion |journal=Obstetrics and Gynecology |volume=104 |issue=1 |pages=174–85 |year=2004 |month=July |pmid=15229018 |doi=10.1097/01.AOG.0000130842.21897.53 |last2=Carr-Ellis |first2=S |last3=Borgatta |first3=L}}</ref><ref>. Americanpregnancy.org (2011-09-20). Retrieved on 2012-02-16.</ref> ]'s ] machine injected a lethal dose of potassium chloride into the patient, which caused the heart to stop functioning, after a ]-induced coma was achieved. A similar device, the ] 'Perfusor', also uses potassium chloride as a suicide aid.<ref>{{cite news | |||
|last = Boyes | |||
|first = Roger | |||
|title = Death for hire – suicide machine lets you push final button | |||
|publisher = The Times | |||
|date = 2008-03-29 | |||
|url = http://www.timesonline.co.uk/tol/news/world/europe/article3641866.ece | |||
|accessdate = 2008-04-25}}</ref><ref>{{cite web | |||
|title = Perfusor compact | |||
|url = http://en.bbraun.bg/doc/doc_download_ir.cfm?uuid=0551260D063AB25B1F5ACC3803CA73A2 | |||
|format = PDF | |||
}}</ref> | |||
==Precautions== | |||
Orally, potassium chloride is toxic in excess; the {{LD50}} is around 2.5 g/kg (meaning that a lethal dose for 50% of people weighing 75 kg (165 ]) is about 190 g (6.7 ]s)). Intravenously, this is reduced to just over 30 mg/kg,<ref> Forensic Sci. vol. 9(1) p. 33-6, 1977.</ref> but of more concern are its severe effects on the cardiac ]s: high doses can cause ] and rapid ], thus the aforementioned use as the third and final drug delivered in the lethal injection process. | |||
==References== | |||
{{reflist|35em}} | |||
*{{RubberBible86th}} <!--Specify page. The citation was the 71st ed. Does the 86th ed. contain the appropriate verification --> | |||
*{{Greenwood&Earnshaw1st}} <!--Specify page --> | |||
{{Potassium compounds}} | {{Potassium compounds}} | ||
{{Chlorides}} | |||
{{Mineral supplements}} | |||
{{Molecules detected in outer space}} | |||
{{Salt topics}} | |||
{{Portal bar | Medicine}} | |||
{{Authority control}} | |||
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Latest revision as of 12:37, 27 December 2024
Ionic compound (KCl) Not to be confused with Potassium chlorate. "KCl" redirects here. For other uses, see KCL (disambiguation). This article is about the salt. For the use of potassium chloride as a medication, see Potassium chloride (medical use). For the use of potassium in biology, see Potassium in biology.Names | |
---|---|
Other names
| |
Identifiers | |
CAS Number | |
3D model (JSmol) | |
ChEBI | |
ChEMBL | |
ChemSpider | |
DrugBank | |
ECHA InfoCard | 100.028.374 |
E number | E508 (acidity regulators, ...) |
KEGG | |
PubChem CID | |
RTECS number |
|
UNII | |
CompTox Dashboard (EPA) | |
InChI
| |
SMILES
| |
Properties | |
Chemical formula | KCl |
Molar mass | 74.555 g·mol |
Appearance | white crystalline solid |
Odor | odorless |
Density | 1.984 g/cm |
Melting point | 770 °C (1,420 °F; 1,040 K) |
Boiling point | 1,420 °C (2,590 °F; 1,690 K) |
Solubility in water | 27.77 g/100mL (0 °C) 33.97 g/100mL (20 °C) 54.02 g/100mL (100 °C) |
Solubility | Soluble in glycerol, alkalies Slightly soluble in alcohol Insoluble in ether |
Solubility in ethanol | 0.288 g/L (25 °C) |
Acidity (pKa) | ~7 |
Magnetic susceptibility (χ) | −39.0·10 cm/mol |
Refractive index (nD) | 1.4902 (589 nm) |
Structure | |
Crystal structure | face centered cubic |
Space group | Fm3m, No. 225 |
Lattice constant | a = 629.2 pm |
Coordination geometry | Octahedral (K) Octahedral (Cl) |
Thermochemistry | |
Std molar entropy (S298) |
83 J·mol·K |
Std enthalpy of formation (ΔfH298) |
−436 kJ·mol |
Pharmacology | |
ATC code | A12BA01 (WHO) B05XA01 (WHO) |
Routes of administration |
Oral, IV, IM |
Pharmacokinetics: | |
Excretion | Kidney: 90%; Fecal: 10% |
Hazards | |
NFPA 704 (fire diamond) | 1 0 0 |
Flash point | Non-flammable |
Lethal dose or concentration (LD, LC): | |
LD50 (median dose) | 2600 mg/kg (oral, rat) |
Safety data sheet (SDS) | ICSC 1450 |
Related compounds | |
Other anions | Potassium fluoride Potassium bromide Potassium iodide |
Other cations | Lithium chloride Sodium chloride Rubidium chloride Caesium chloride Ammonium chloride |
Related compounds | Potassium hypochlorite Potassium chlorite Potassium chlorate Potassium perchlorate |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa). N verify (what is ?) Infobox references |
Potassium chloride (KCl, or potassium salt) is a metal halide salt composed of potassium and chlorine. It is odorless and has a white or colorless vitreous crystal appearance. The solid dissolves readily in water, and its solutions have a salt-like taste. Potassium chloride can be obtained from ancient dried lake deposits. KCl is used as a fertilizer, in medicine, in scientific applications, domestic water softeners (as a substitute for sodium chloride salt), and in food processing, where it may be known as E number additive E508.
It occurs naturally as the mineral sylvite, which is named after salt's historical designations sal degistivum Sylvii and sal febrifugum Sylvii, and in combination with sodium chloride as sylvinite.
Uses
Fertilizer
The majority of the potassium chloride produced is used for making fertilizer, called potash, since the growth of many plants is limited by potassium availability. The term "potash" refers to various mined and manufactured salts that contain potassium in water-soluble form. Potassium chloride sold as fertilizer is known as "muriate of potash"—it is the common name for potassium chloride (KCl) used in agriculture. The vast majority of potash fertilizer worldwide is sold as muriate of potash. The dominance of muriate of potash in the fertilizer market is due to its high potassium content (approximately 60% K
2O equivalent) and relative affordability compared to other potassium sources like sulfate of potash (potassium sulfate). Potassium is one of the three primary macronutrients essential for plant growth, alongside nitrogen and phosphorus. Potassium plays a vital role in various plant physiological processes, including enzyme activation, photosynthesis, protein synthesis, and water regulation. For watering plants, a moderate concentration of potassium chloride (KCl) is used to avoid potential toxicity: 6 mM (millimolar) is generally effective and safe for most plants, that is approximately 0.4 grams (0.014 oz) per liter of water.
Medical use
Main article: Potassium chloride (medical use)Potassium is vital in the human body, and potassium chloride by mouth is the standard means to treat low blood potassium, although it can also be given intravenously. It is on the World Health Organization's List of Essential Medicines. It is also an ingredient in Oral Rehydration Therapy (ORT)/solution (ORS) to reduce hypokalemia caused by diarrhoea. This is another medicine on the WHO's List of Essential Medicines.
Potassium chloride contains 52% of elemental potassium by mass.
Overdose causes hyperkalemia which can disrupt cell signaling to the extent that the heart will stop, reversibly in the case of some open heart surgeries.
Culinary use
Potassium chloride can be used as a salt substitute for food, but due to its weak, bitter, unsalty flavor, it is often mixed with ordinary table salt (sodium chloride) to improve the taste, to form low sodium salt. The addition of 1 ppm of thaumatin considerably reduces this bitterness. Complaints of bitterness or a chemical or metallic taste are also reported with potassium chloride used in food.
Execution
In the United States, potassium chloride is used as the final drug in the three-injection sequence of lethal injection as a form of capital punishment. It induces cardiac arrest, ultimately killing the inmate.
Industrial
This section needs additional citations for verification. Please help improve this article by adding citations to reliable sources in this section. Unsourced material may be challenged and removed. (September 2022) (Learn how and when to remove this message) |
As a chemical feedstock, the salt is used for the manufacture of potassium hydroxide and potassium metal. It is also used in medicine, lethal injections, scientific applications, food processing, soaps, and as a sodium-free substitute for table salt for people concerned about the health effects of sodium.
It is used as a supplement in animal feed to boost the potassium level in the feed. As an added benefit, it is known to increase milk production.
It is sometimes used in solution as a completion fluid in petroleum and natural gas operations, as well as being an alternative to sodium chloride in household water softener units.
Glass manufacturers use granular potash as a flux, lowering the temperature at which a mixture melts. Because potash imparts excellent clarity to glass, it is commonly used in eyeglasses, glassware, televisions, and computer monitors.
Because natural potassium contains a tiny amount of the isotope potassium-40, potassium chloride is used as a beta radiation source to calibrate radiation monitoring equipment. It also emits a relatively low level of 511 keV gamma rays from positron annihilation, which can be used to calibrate medical scanners.
Potassium chloride is used in some de-icing products designed to be safer for pets and plants, though these are inferior in melting quality to calcium chloride. It is also used in various brands of bottled water.
Potassium chloride was once used as a fire extinguishing agent, and in portable and wheeled fire extinguishers. Known as Super-K dry chemical, it was more effective than sodium bicarbonate-based dry chemicals and was compatible with protein foam. This agent fell out of favor with the introduction of potassium bicarbonate (Purple-K) dry chemical in the late 1960s, which was much less corrosive, as well as more effective. It is rated for B and C fires.
Along with sodium chloride and lithium chloride, potassium chloride is used as a flux for the gas welding of aluminium.
Potassium chloride is also an optical crystal with a wide transmission range from 210 nm to 20 μm. While cheap, KCl crystals are hygroscopic. This limits its application to protected environments or short-term uses such as prototyping. Exposed to free air, KCl optics will "rot". Whereas KCl components were formerly used for infrared optics, they have been entirely replaced by much tougher crystals such as zinc selenide.
Potassium chloride is used as a scotophor with designation P10 in dark-trace CRTs, e.g. in the Skiatron.
Toxicity
The typical amounts of potassium chloride found in the diet appear to be generally safe. In larger quantities, however, potassium chloride is toxic. The LD50 of orally ingested potassium chloride is approximately 2.5 g/kg, or 190 grams (6.7 oz) for a body mass of 75 kilograms (165 lb). In comparison, the LD50 of sodium chloride (table salt) is 3.75 g/kg.
Intravenously, the LD50 of potassium chloride is far smaller, at about 57.2 mg/kg to 66.7 mg/kg; this is found by dividing the lethal concentration of positive potassium ions (about 30 to 35 mg/kg) by the proportion by mass of potassium ions in potassium chloride (about 0.52445 mg K/mg KCl).
Chemical properties
Solubility
KCl is soluble in a variety of polar solvents.
Solvent | Solubility (g/kg of solvent at 25 °C) |
---|---|
Water | 360 |
Liquid ammonia | 0.4 |
Liquid sulfur dioxide | 0.41 |
Methanol | 5.3 |
Ethanol | 0.37 |
Formic acid | 192 |
Sulfolane | 0.04 |
Acetonitrile | 0.024 |
Acetone | 0.00091 |
Formamide | 62 |
Acetamide | 24.5 |
Dimethylformamide | 0.17–0.5 |
Solutions of KCl are common standards, for example for calibration of the electrical conductivity of (ionic) solutions, since KCl solutions are stable, allowing for reproducible measurements. In aqueous solution, it is essentially fully ionized into solvated K and Cl ions.
Redox and the conversion to potassium metal
Although potassium is more electropositive than sodium, KCl can be reduced to the metal by reaction with metallic sodium at 850 °C because the more volatile potassium can be removed by distillation (see Le Chatelier's principle):
This method is the main method for producing metallic potassium. Electrolysis (used for sodium) fails because of the high solubility of potassium in molten KCl.
Other potassium chloride stoichiometries
Potassium chlorides with formulas other than KCl have been predicted to become stable under pressures of 20 GPa or more. Among these, two phases of KCl3 were synthesized and characterized. At 20-40 GPa, a trigonal structure containing K and Cl3 is obtained; above 40 GPa this gives way to a phase isostructural with the intermetallic compound Cr3Si.
Physical properties
Under ambient conditions, the crystal structure of potassium chloride is like that of NaCl. It adopts a face-centered cubic structure known as the B1 phase with a lattice constant of roughly 6.3 Å. Crystals cleave easily in three directions. Other polymorphic and hydrated phases are adopted at high pressures.
Some other properties are
- Transmission range: 210 nm to 20 μm
- Transmittivity = 92% at 450 nm and rises linearly to 94% at 16 μm
- Refractive index = 1.456 at 10 μm
- Reflection loss = 6.8% at 10 μm (two surfaces)
- dN/dT (expansion coefficient)= −33.2×10/°C
- dL/dT (refractive index gradient)= 40×10/°C
- Thermal conductivity = 0.036 W/(cm·K)
- Damage threshold (Newman and Novak): 4 GW/cm or 2 J/cm (0.5 or 1 ns pulse rate); 4.2 J/cm (1.7 ns pulse rate Kovalev and Faizullov)
As with other compounds containing potassium, KCl in powdered form gives a lilac flame.
Production
Potassium chloride is extracted from minerals sylvite, carnallite, and potash. It is also extracted from salt water and can be manufactured by crystallization from solution, flotation or electrostatic separation from suitable minerals. It is a by-product of the production of nitric acid from potassium nitrate and hydrochloric acid.
Most potassium chloride is produced as agricultural and industrial-grade potash in Saskatchewan, Canada, Russia, and Belarus. Saskatchewan alone accounted for over 25% of the world's potash production in 2017.
Laboratory methods
Potassium chloride is inexpensively available and is rarely prepared intentionally in the laboratory. It can be generated by treating potassium hydroxide (or other potassium bases) with hydrochloric acid:
This conversion is an acid-base neutralization reaction. The resulting salt can then be purified by recrystallization. Another method would be to allow potassium to burn in the presence of chlorine gas, also a very exothermic reaction:
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Further reading
- Lide DR, ed. (2005). CRC Handbook of Chemistry and Physics (86th ed.). Boca Raton, Florida: CRC Press. ISBN 0-8493-0486-5.
- Greenwood NN, Earnshaw A (1984). Chemistry of the Elements. Oxford: Pergamon Press. ISBN 978-0-08-022057-4.
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