Potassium chloride
159292
225614952
2008-07-14T15:50:37Z
132.72.8.115
/* Precautions */
{{chembox new
| ImageFile = Potassium chloride.jpg
| ImageFile1 = Potassium-chloride-3D-ionic.png
| OtherNames = [[sylvite]] (mineral form); muriate of potash
| Section1 = {{Chembox Identifiers
| CASNo = 7447-40-7
}}
| Section2 = {{Chembox Properties
| Formula = KCl
| MolarMass = 74.551 [[g/mol]]
| Appearance = white crystalline [[solid]]
| Density = 1.987 g/cm<sup>3</sup>
| Solubility = 28.1 [[gram|g]]/100 [[centimetre|cm]]³ (0°C);
34.0 [[gram|g]]/100 [[cm³]] (20[[°C]]);
56.7 gram|g/100 cm³ (100°C);
| MeltingPt = 776 °C
}}
| Section3 = {{Chembox Structure
| Structure = [[crystal structure|Face-centred cubic]]
}}
| Section7 = {{Chembox Hazards
| LD50 = 2600 mg/kg (oral/rat), 142 mg/kg (intravenous/rat)<ref> ''Sigma Material Safety Data Sheet - Potassium Chloride''. Section 11. Sigma Chemical Company. Valid 7/2001.</ref>
}}
| Section8 = {{Chembox Related
| Function = Compounds
| OtherAnions = [[potassium fluoride]]; [[potassium bromide]]; [[potassium iodide]]
| OtherCations = [[sodium chloride]];[[rubidium chloride]]
}}
}}
The [[chemical compound]] '''potassium chloride''' (KCl) is a [[metal]] [[halide]] [[Salt (chemistry)|salt]] composed of [[potassium]] and [[chlorine]]. In its pure state it is [[odor]]less. It has a white or [[color]]less [[vitreous]] [[crystal]], with a [[crystal structure]] that cleaves easily in three directions. Potassium chloride crystals are face-centered cubic. Potassium chloride is also commonly known as "[[Muriate]] of Potash". [[Potash]] varies in color from pink or red to white depending on the [[mining]] 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 fertilizer]]s. KCl is used in [[medicine]], scientific applications, [[Food preservation|food processing]] and in judicial [[Execution (legal)|execution]] through [[lethal injection]]. It occurs naturally as the [[mineral]] [[sylvite]] and in combination with [[sodium chloride]] as [[sylvinite]].
==Chemical properties==
Potassium chloride can react as a source of [[chloride]] [[ion]]. As with any other [[Solubility|soluble]] ionic chloride, it will precipitate insoluble chloride [[salt]]s when added to a [[solution]] of an appropriate metal ion:
:KCl([[aqueous|aq]]) + [[silver nitrate|AgNO<sub>3</sub>]](aq) → [[silver(I) chloride|AgCl]]([[solid|s]]) + KNO<sub>3</sub>(aq)
Although potassium is more [[electropositive]] than [[sodium]], KCl can be reduced to the metal by reaction with metallic sodium at 850 °C because the potassium is removed by distillation (see [[Le Chatelier's principle]]):
:KCl(l) + Na(l) ⇌ NaCl(l) + K(g)
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.
As with other compounds containing potassium, KCl in powdered form gives a lilac [[flame test]] result.
==Manufacture/Extraction==
Potassium chloride occurs naturally as [[sylvite]], and it can be extracted from [[sylvinite]]. It is also extracted from [[Brine|salt water]] and can be manufactured by crystallization from [[solution]], [[flotation process|flotation]] or [[electrostatic]] separation from suitable minerals. It is a by-product of the making of [[nitric acid]] from [[potassium nitrate]] and [[hydrochloric acid]].
==Uses==
The majority of the potassium chloride produced is used for making [[fertilizer]], since the growth of many [[plant]]s is limited by their potassium intake. As a chemical [[feedstock]] it is used for the [[manufacture]] of [[potassium hydroxide]] and potassium metal. It is also used in medicine, [[Science|scientific]] applications, food processing, and as a sodium-free substitute for [[edible salt|table salt]] (sodium chloride). Potassium chloride is also used as the third of a three drug combination in [[judicial]] [[Execution (legal)|execution]] through [[lethal injection]]. It is sometimes used in [[water]] as a completion fluid in [[petroleum]] and [[natural gas]] operations, as well as being an alternative to sodium chloride in household [[water softener]] units. KCl is useful as a [[beta radiation]] source for calibration of [[radiation monitoring equipment]] because natural potassium contains 0.0118% of the [[isotope]] <sup>40</sup>K. One [[kilogram]] of KCl yields 16350 [[becquerel]]s of [[radiation]] consisting of 89.28% beta and 10.72% [[gamma ray|gamma]] with 1.46083 MeV. Potassium chloride makes up 70% of [[Ace Hardware]]'s [[pet]] and [[vegetarian]]-friendly "Ice Melt" though inferior in melting quality to calcium chloride (0[[°F]] v. -25°F). It is also used in [[Dasani|Dasani water]], as well as in bulk quantities for [[fossil fuel]] [[drilling]] purposes.
==Biological and medical properties==
Potassium is vital in the [[human body]] and oral potassium chloride is the common means to replenish it, although it can also be diluted and given [[Intravenous therapy|intravenously]] (of course, in concentrations much lower than those used in executions). It can be used as a [[salt substitute]] for [[food]], but due to its weak, bitter, unsalty [[flavor]], it is usually mixed with regular salt (sodium chloride), for this purpose to improve the [[taste]] (for example, in Morton Lite Salt<ref>{{cite web
| title = Lite Salt™ Mixture
| publisher = Morton Solt
| url = http://www.mortonsalt.com/products/foodsalts/Lite_Salt.htm
| accessdate = 2008-04-25}}</ref>). Medically it is used in the treatment of [[hypokalemia]] and associated conditions, for [[digitalis]] [[poison]]ing, and as an [[electrolyte]] replenisher. Brand names include K-Dur, Klor-Con, Micro-K, and Kaon Cl. Side effects can include [[gastrointestinal tract|gastrointestinal]] discomfort including [[nausea]] and [[vomiting]], [[diarrhea]] and [[bleeding]] of the digestive tract. [[Overdose]]s cause [[hyperkalemia]] which can lead to [[paresthesia]], [[Heart|cardiac]] conduction blocks, [[fibrillation]], [[Cardiac arrhythmia|arrhythmias]], and [[sclerosis]].
Dr. [[Jack Kevorkian]]'s [[thanatron]] machine injected a lethal dose of potassium chloride into the patient, which caused the heart to stop functioning, after a [[sodium thiopental]]-induced coma was achieved. A similar device, the [[Germany|German]] '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>
==Physical properties==
Potassium chloride has a crystalline structure like many other salts. Its structure is face-centered cubic. Its [[lattice]] constant is roughly 6.3 [[angstrom]]s.
In [[chemistry]] and [[physics]] it is a very commonly used as a standard, for example as a [[calibration]] standard solution in measuring [[electrical conductivity]] of (ionic) solutions, since carefully prepared KCl solutions have well-reproducible and well-repeatable measurable properties.
{| class="toccolours" border="1" style="margin: 1em; border-collapse: collapse;"
! {{chembox header}} | Solubility of KCl in various solvents<br/ >(g KCl / 100 g of solvent at 25 °C)
|-
| [[Water (molecule)|H<sub>2</sub>O]] || 36
|-
| [[Ammonia|Liquid ammonia]] || 0.04
|-
| [[Sulfur dioxide|Liquid sulfur dioxide]] || 0.041
|-
| [[Methanol]] || 0.53
|-
| [[Formic acid]] || 19.2
|-
| [[Sulfolane]] || 0.004
|-
| [[Acetonitrile]] || 0.0024
|-
| [[Acetone]] || 0.000091
|-
| [[Formamide]] || 6.2
|-
| [[Acetamide]] || 2.45
|-
| [[Dimethylformamide]] || 0.017 - 0.05
|-
| Colspan = 2| Reference:<br />Burgess, J. ''Metal Ions in Solution''<br />(Ellis Horwood, New York, 1978)<br />ISBN 0-85312-027-7
|}
==Precautions==
Orally it is toxic in excess; the [[LD50|LD<sub>50</sub>]] is around 2500 [[milligram]]/kg (meaning that a person weighing 75 kg (165 [[Pound (mass)|lb]]) would have to consume about 190 g (6.7 [[ounce]]s) which equivalent to 38 tea spoons; [[sodium chloride|table salt]] is about as toxic). Intravenously this is reduced to just over 100 mg/kg but of more concern are its severe effects on cardiac [[muscle]]s; high doses can cause [[cardiac arrest]] and rapid [[death]]. A massive overdose of intravenous potassium chloride is used to stop the heart in capital punishment by lethal injection.
==References==
<references />
* ''Handbook of Chemistry and Physics'', 71st edition, CRC Press, Ann Arbor, Michigan, 1990.
* N. N. Greenwood, A. Earnshaw, ''Chemistry of the Elements'', Pergamon Press, 1984. ISBN 0-08-022057-6
* "Sigma Material Safety Data Sheet - Potassium Chloride", Valid 7/2001.
<!--Categories-->
[[Category:Chlorides]]
[[Category:Dietary minerals]]
[[Category:Lethal injection components]]
[[Category:Metal halides]]
[[Category:Potassium compounds]]
[[Category:Edible salt]]
[[Category:Agricultural chemicals]]
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[[bg:Калиев хлорид]]
[[bs:Kalijum hlorid]]
[[ca:Clorur de potassi]]
[[cs:Chlorid draselný]]
[[de:Kaliumchlorid]]
[[es:Cloruro de potasio]]
[[fr:Chlorure de potassium]]
[[gl:Cloruro de potasio]]
[[he:אשלגן כלורי]]
[[it:Cloruro di potassio]]
[[lv:Kālija hlorīds]]
[[lt:Kalio chloridas]]
[[hu:Kálium-klorid]]
[[nl:Kaliumchloride]]
[[ja:塩化カリウム]]
[[no:Kaliumklorid]]
[[pl:Chlorek potasu]]
[[pt:Cloreto de potássio]]
[[ru:Хлорид калия]]
[[sr:Калијум хлорид]]
[[fi:Kaliumkloridi]]
[[sv:Kaliumklorid]]
[[tr:Potasyum klorür]]
[[uk:Хлорид калію]]
[[zh:氯化钾]]