View source for Potassium chloride

{{chembox
| Watchedfields = changed
| verifiedrevid = 262759781
| ImageFile = Potassium chloride.jpg
| ImageFile1 = Potassium-chloride-3D-ionic.png
| OtherNames = [[Sylvite]]<br/>Muriate of potash
| Section1 = {{Chembox Identifiers
| CASNo = 7447-40-7
| CASNo_Ref = {{cascite}}
| ChemSpiderID = 4707
| PubChem = 4873
| RTECS = TS8050000
}}
| Section2 = {{Chembox Properties
| Formula = KCl
| MolarMass = 74.551 g/mol
| Appearance = white crystalline solid
| Odor = odorless
| Density = 1.984 g/cm<sup>3</sup>
| Solubility = 281 g/L (0 °C) <br> 344 g/L (20 °C) <br> 567 g/L (100 °C)
| SolubleOther = soluble in [[ether]], [[glycerol]], [[alkali]]es <br> slightly soluble in [[alcohol]]
| MeltingPt = 770 °C
| BoilingPt = 1420 °C (sublimes)
| RefractIndex = 1.33743
| pKa = ~7
}}
| Section3 = {{Chembox Structure
| CrystalStruct = [[Cubic crystal system#Rock-salt structure|face centered cubic]]
}}
| Section7 = {{Chembox Hazards
| ExternalMSDS = [http://www.ilo.org/public/english/protection/safework/cis/products/icsc/dtasht/_icsc14/icsc1450.htm ICSC 1450]
| EUIndex = Not listed
| FlashPt = Non-flammable
| NFPA-H = 1
| NFPA-F = 0
| NFPA-R = 0
| NFPA-O =
| LD50 = 2600 mg/kg (oral/rat), 142 mg/kg (intravenous/rat)<ref>{{Cite book|title = Material Safety Data Sheet - Potassium Chloride|publisher = Sigma–Aldrich|date = July 2001}}</ref>
}}
| Section8 = {{Chembox Related
| OtherAnions = [[Potassium fluoride]]<br/>[[Potassium bromide]]<br/>[[Potassium iodide]]
| OtherCations = [[Lithium chloride]]<br/>[[Sodium chloride]]<br/>[[Rubidium chloride]]<br/>[[Caesium 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 occasionally known as "[[muriate]] of potash," particularly when used as a [[fertilizer]]. [[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==
In [[chemistry]] and [[physics]] it is a very commonly used 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.

<div style="float:left; margin:5px;">
{| class="toccolours" border="1" style="margin: 1em; border-collapse: collapse;"
! {{chembox header}}|Solubility of KCl in various solvents<br/ >(g&nbsp;KCl&nbsp;/&nbsp;100&nbsp;g of solvent at 25&nbsp;°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>
|-
| [[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
|}
</div>

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&nbsp;°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.

==Physical properties==
Potassium chloride has a crystalline structure like many other salts. Its structure is face-centered cubic. Its [[Crystal structure|lattice]] constant is roughly 630 [[picometer]]s. Some other properties are
*Transmission range: 210&nbsp;nm to 20&nbsp;µm
*[[Transmittance|Transmittivity]] = 92% at 450&nbsp;nm and rises linearly to 94% at 16&nbsp;µm
*Refractive index = 1.456 at 10&nbsp;µm
*Reflection Loss = 6.8% at 10&nbsp;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==
[[File:Sylvin (aka).jpg|thumb|left|150px|Sylvite]]
[[File:Sylvinite.jpg|thumb|left|150px|Sylvinite]]
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 used as the third of a three-drug combination in [[lethal injection]]. Additionally, KCl is used (albeit rarely) in fetal intracardiac injections in second- and third-trimester [[induced abortion]]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>[http://www.americanpregnancy.org/unplannedpregnancy/abortionprocedures.html Types of Abortion Procedures]</ref>

It is sometimes used in [[water]] as a [[Completion (oil and gas wells)|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 vegetation-friendly "Ice Melt" though inferior in melting quality to [[calcium chloride]] ({{convert|0|F|C}} v. {{convert|-25|F|C}}). It is also used in various brands of [[bottled water]], as well as in bulk quantities for [[fossil fuel]] [[drilling]] purposes.

Potassium chloride was once used as a [[fire retardant|fire extinguishing agent]], used in portable and wheeled [[fire extinguisher]]s. Known as Super-K dry chemical, it was more effective than [[sodium bicarbonate]]-based dry chemicals and was compatible with [[fire fighting foam|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]] and more effective. It is rated for B and C fires.

Along with [[sodium chloride]] and [[lithium chloride]], potassium chloride is used as a [[Flux (metallurgy)|flux]] for the [[gas welding]] of [[aluminium]].

Potassium chloride is also an optical crystal with a wide transmission range from 210&nbsp;nm to 20&nbsp;µm. While cheap, KCl crystal is [[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]], it has been entirely replaced by much tougher crystals like [[Zinc selenide|ZnSe]].

Potassium chloride has also been used to create [[heating pad|heat packs]] which employ [[exothermic]] [[chemical reaction]]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 [[crystallization]] of [[sodium acetate]] (multiple use products).

Potassium chloride is used as a [[scotophor]] with designation '''P10''' in [[dark-trace CRT]]s, e.g. in the [[Skiatron]].

==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]]. 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]]. Medically it is used in the treatment of [[hypokalemia]] and associated conditions, for [[digitalis]] [[poison]]ing, and as an [[electrolyte]] replenisher.<ref>[http://emedicine.medscape.com/article/767448-treatment Hypokalemia: Treatment & Medication]</ref> Brand names include K-Dur, Klor-Con, Micro-K, Slow-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 (medicine)|sclerosis]].<ref>[http://emedicine.medscape.com/article/766479-overview Hyperkalemia]</ref> Prescription potassium citrate (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|pmid=15723964|last2=Markandu|first2=ND|last3=Coltart|first3=R|last4=Barron|first4=J|last5=MacGregor|first5=GA|issue=4}}</ref> 

The lethal effects of potassium chloride overdoses has led to its use in lethal injection. [[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>

==Precautions==
Orally, KCl is toxic in excess; the [[LD50|LD<sub>50</sub>]] is around 2.5 g/kg (meaning that a lethal dose for 50% of people weighing 75&nbsp;kg (165 [[Pound (mass)|lb]]) is about 190 g (6.7 [[ounce]]s). Intravenously this is reduced to just over 100&nbsp;mg/kg, but of more concern are its severe effects on the cardiac [[muscle]]s; high doses can cause [[cardiac arrest]] and rapid [[death]], ergo its aforementioned use as the third and final drug delivered in the lethal injection process.

==References==
{{reflist|2}}
*{{RubberBible86th}} <!--Specify page.  The citation was the 71st ed. Does the 86th ed. contain the appropriate verification -->
*{{Greenwood&Earnshaw1st}} <!--Specify page -->

{{Potassium compounds}}

<!--Categories-->
[[Category:Chlorides]]
[[Category:Dietary minerals]]
[[Category:Lethal injection components]]
[[Category:Metal halides]]
[[Category:Potassium compounds]]
[[Category:Edible salt]]
[[Category:Fertilizers]]
[[Category:World Health Organization essential medicines]]

<!--Other languages-->

[[ar:كلوريد البوتاسيوم]]
[[bs:Kalijum hlorid]]
[[bg:Калиев хлорид]]
[[ca:Clorur de potassi]]
[[cs:Chlorid draselný]]
[[de:Kaliumchlorid]]
[[et:Kaaliumkloriid]]
[[es:Cloruro de potasio]]
[[fa:پتاسیم کلرید]]
[[fr:Chlorure de potassium]]
[[gl:Cloruro de potasio]]
[[hr:Kalijev klorid]]
[[it:Cloruro di potassio]]
[[he:אשלגן כלורי]]
[[ka:კალიუმის ქლორიდი]]
[[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]]
[[th:โพแทสเซียมคลอไรด์]]
[[tr:Potasyum klorür]]
[[uk:Хлорид калію]]
[[zh:氯化钾]]
[[Category:2Fix]]