View source for Sodium chloride

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{{about|the chemical compound|sodium chloride in the diet|Salt|sodium chloride as a mineral|Halite}}
{{chembox
| Watchedfields = changed
| verifiedrevid = 262758507
| Name = Sodium chloride
| ImageFile = Sodiumchloride crystal 01.jpg
| ImageFile1 = Sodium-chloride-3D-ionic.png
| IUPACName = Sodium chloride
| OtherNames = Common salt, [[halite]], [[table salt]], rock salt, saline, hyposaline, sodium monochloride, sodium chloric, saltex<ref>[http://webbook.nist.gov/cgi/cbook.cgi?ID=C7647145&Type=THZ-IR-SPEC&Index=1 National Institute of Standards and Technology: Sodium Chloride]</ref> 
| Section1 = {{Chembox Identifiers
| CASNo = 7647-14-5
| CASNo_Ref = {{cascite}}
| PubChem = 5234
| ChemSpiderID = 5044
| RTECS = VZ4725000
 }}
| Section2 = {{Chembox Properties
| Formula = [[Sodium|Na]][[Chlorine|Cl]]
| MolarMass = 58.443 g/mol
| Appearance = Colorless/white crystalline solid
| Odor = Odorless
| Solubility = 356 g/L (0 °C)<br/>359 g/L (25 °C)<br/>391 g/L (100 °C) 
| Solvent1 = methanol
| Solubility1 = 14.9 g/L
| Solvent2 = ammonia
| Solubility2 = 21.5 g/L
| SolubleOther = soluble in [[glycerol]], [[ethylene glycol]], [[formic acid]]<br/>insoluble in [[hydrochloric acid|HCl]]
| Density = 2.165 g/cm<sup>3</sup>
| MeltingPtC = 801 
| BoilingPtC = 1413
| RefractIndex = 1.5442 (589 nm)
| pKa = 6.7–7.3
 }}
| Section3 = {{Chembox Structure
| CrystalStruct = Face-centered cubic <br>(''see text''), [[Pearson symbol|cF8]]
| SpaceGroup = Fm{{overline|3}}m, No. 225
| Coordination = Octahedral (Na<sup>+</sup>)<br/>Octahedral (Cl<sup>–</sup>)
| LattConst_a = 564.02 pm
 }}
| Section7 = {{Chembox Hazards
| ExternalMSDS = 
| EUIndex = Not listed
| NFPA-H = 0
| NFPA-F = 0
| NFPA-R = 0
| FlashPt = Non-flammable
| RPhrases = 
| SPhrases = 
| LD50 = 3000–8000 mg/kg (oral in rats, mice, rabbits)<ref>{{Cite book|author = Martel, B.; Cassidy, K.|title = Chemical Risk Analysis: A Practical Handbook|publisher = Butterworth–Heinemann|year = 2004|page = 369|isbn = 1903996651|postscript = <!--None-->}}</ref>
 }}
| Section8 = {{Chembox Related
| OtherAnions = [[Sodium fluoride]]<br/>[[Sodium bromide]]<br/>[[Sodium iodide]]
| OtherCations = [[Lithium chloride]]<br/>[[Potassium chloride]]<br/>[[Rubidium chloride]]<br/>[[Caesium chloride]]
 }}
}}

'''Sodium chloride''', also known as '''salt''', ''' common salt''', '''table salt''', or [[halite]], is an [[ionic compound]] with the [[chemical formula|formula]] [[Sodium|Na]][[Chloride|Cl]]. Sodium chloride is the [[salt (chemistry)|salt]] most responsible for the salinity of the [[ocean]] and of the [[extracellular fluid]] of many multicellular [[organism]]s. As the major ingredient in [[edible salt]], it is commonly used as a [[condiment]] and food [[preservative]].

==Production and use==

[[Image:Salt mine 0096.jpg|thumb|left|Modern rock salt mine near [[Mount Morris, New York|Mount Morris]], [[New York]], [[United States]]]]
Salt is currently [[Mass production|mass-produced]] by [[evaporation]] of [[seawater]] or [[brine]] from other sources, such as [[brine well]]s and [[salt lake (geography)|salt lake]]s, and by [[salt mine|mining]] '''rock salt''', called [[halite]]. In 2009, world production was estimated at 260 million [[metric ton]]s, the top five producers (in million tonnes) being China (60.0), United States (46.0), Germany (16.5), India (15.8) and Canada (14.0).<ref>[http://minerals.usgs.gov/minerals/pubs/commodity/salt/mcs-2010-salt.pdf Salt], U.S. Geological Survey</ref>

As well as the familiar uses of salt in [[cooking]], salt is used in many applications, from [[manufacturing]] pulp and paper, to setting dyes in textiles and fabric, to producing [[soap]]s, [[detergent]]s, and other bath products. It is the major source of industrial chlorine and [[sodium hydroxide]], and used in almost every industry.

Sodium chloride is sometimes used as a cheap and safe [[desiccant]] because it appears to have [[hygroscopic]] properties, making [[Salting (food)|salting]] an effective method of [[food preservation]] historically; the salt draws water out of bacteria through [[osmotic pressure]], keeping it from reproducing, a major source of food spoilage. Even though more effective desiccants are available, few are safe for humans to ingest. 

{| class="toccolours" border="1" align="left" style="margin: 1em; border-collapse: collapse;"
! {{chembox header}}|Solubility of NaCl in various solvents<br/ >(g NaCl / 1 kg of solvent at 25 °C)<ref>Burgess, J. ''Metal Ions in Solution'' (Ellis Horwood, New York, 1978) ISBN 0-85312-027-7</ref>
|-
| [[Water (molecule)|H<sub>2</sub>O]] || 360
|-
| [[Ammonia|Liquid ammonia]] || 30.2
|-
| [[glycerin]] || 83
|-
| [[propylene glycol]] || 71
|-
| [[Methanol]] || 14
|-
| [[Ethanol]] || 0.65
|-
| [[1-propanol]] || 0.124
|-
| [[2-propanol]] || 0.03
|-
| [[1-butanol]] || 0.05
|-
| [[1-pentanol]] || 0.018
|-
| [[Sulfolane]] || 0.05
|-
| [[Formic acid]] || 52
|-
| [[Acetone]] || 0.00042
|-
| [[Formamide]] || 94
|-
| [[Acetonitrile]] || 0.003
|-
| [[Dimethylformamide]] || 0.4
|}

===Synthetic uses===
Uses of chlorine include [[Polyvinyl chloride|PVC]], [[pesticide]]s and [[epoxy]] [[resin]]s. Industrially, elemental chlorine is usually produced by the [[electrolysis]] of sodium chloride dissolved in water. Along with chlorine, this [[chloralkali process]] yields [[hydrogen]] gas and [[sodium hydroxide]], according to the [[chemical equation]]

:2 NaCl + 2 H<sub>2</sub>O → Cl<sub>2</sub> + H<sub>2</sub> + 2 NaOH

Sodium metal is produced commercially through the electrolysis of liquid sodium chloride. This is now done in a [[Downs Cell|Down's cell]] in which sodium chloride is mixed with [[calcium chloride]] to lower the melting point below 700 °C. As calcium is more electropositive than sodium, no calcium will be formed at the cathode. This method is less expensive than the previous method of electrolyzing sodium hydroxide. 

Sodium chloride is used in other chemical processes for the large-scale production of compounds containing sodium or chlorine. In the [[Solvay process]], sodium chloride is used for producing [[sodium carbonate]] and [[calcium chloride]]. In the [[Mannheim process]] and in the [[Hargreaves process]], it is used for the production of [[sodium sulfate]] and [[hydrochloric acid]].

===Biological uses===
Many [[micro organism]]s cannot live in an overly salty environment: water is drawn out of their [[cell (biology)|cells]] by [[osmosis]]. For this reason salt is used to [[Food preservation|preserve]] some foods, such as smoked bacon or fish. It can also be used to detach [[leeches]] that have attached themselves to feed. It is also used to disinfect wounds.

===Optical uses===
Pure NaCl crystal is an optical compound with a wide transmission range from 200&nbsp;nm to 20&nbsp;µm. It was often used in the infrared spectrum range and it is still used sometimes.

While inexpensive, NaCl crystal is soft and [[Hygroscopy|hygroscopic]]. When exposed to free air, NaCl optics gradually covers with "frost". This limits application of NaCl to protected environments or for short-term uses such as prototyping. 

Today tougher crystals like [[zinc selenide]] (ZnSe) are used instead of NaCl (for the IR spectral range).

===Optical data===

*Transmitivity: 92% (from 400&nbsp;nm to 13 μm)
* Refractive Index: 1.494 at 10 μm
* Reflection Loss: 7.5% at 10 μm (2 surfaces)
* dN/dT: −36.2×10<sup>−6</sup>/°C at 0.7 μm

===Household uses===
Since at least [[medieval]] times, people have used salt as a cleansing agent rubbed on household surfaces. It is also used in many brands of [[shampoo]], and popularly to de-ice driveways and patches of ice.

===Firefighting uses===
[[Image:Metlx.jpg|thumb|left|upright|A class D fire extinguisher for various metals]]
Sodium chloride is the principal extinguishing agent in fire extinguishers (Met-L-X, Super D) used on combustible metal fires such as magnesium, potassium, sodium, and NaK alloys (Class D). Thermoplastic powder is added to the mixture, along with waterproofing (metal stearates) and anti-caking materials (tricalcium phosphate) to form the extinguishing agent. When it is applied to the fire, the salt acts like a heat sink, dissipating heat from the fire, and also forms an oxygen-excluding crust to smother the fire. The plastic additive melts and helps the crust maintain its integrity until the burning metal cools below its ignition temperature. This type of extinguisher was invented in the late 1940s in the cartridge-operated type shown here, although stored pressure versions are now popular. Common sizes are 30&nbsp;lb. portable and 350&nbsp;lb. wheeled.

===In weather===
[[Image:Clouds from above.JPG|thumb|Clouds above the [[Pacific]]]]
Small particles of [[sea salt]] are the dominant [[cloud condensation nuclei]] well out at sea, which allow the formation of [[cloud]]s in otherwise non-polluted [[air]].<ref>{{cite journal|doi=10.1002/qj.49712757609|url=http://www3.interscience.wiley.com/journal/114028130/abstract|title=The role of sea-salt particles as cloud condensation nuclei over the remote oceans|author=B. J. Mason|journal=The Quarterly Journal of the Royal Meteorological Society|volume=127|issue=576|pages=2023–2032|date=2006-12-19|accessdate=2009-07-08}}</ref> [[Snow removal]] by addition of salt (salting) is done to make travel easier and safer, and decrease the long term impact of a heavy [[snow]]fall on human populations. This process is done by both individual households and by governments and institutions and utilizes salts to eliminate snow from road surfaces and sidewalks.<ref>{{cite book|url=http://books.google.com/?id=I3gxuwTE5_MC&pg=PA10&lpg=PA10&dq=effect+of+snowfall+on+infrastructure|title=Managing roadway snow and ice control operations|author=David A. Kuemmel|page=10|isbn=9780309056663|publisher=Transportation Research Board|year=1994|accessdate=2009-07-08}}</ref>

==Biological functions==
{{for|further information about sodium chloride in the diet|Salt}}
In humans, a high-salt intake has long been suspected to generally raise blood pressure. More recently, it was demonstrated to attenuate [[nitric oxide]] production. Nitric oxide (NO) contributes to vessel [[homeostasis]] by inhibiting vascular smooth muscle contraction and growth, platelet aggregation, and leukocyte adhesion to the [[endothelium]].<ref>[http://content.karger.com/ProdukteDB/produkte.asp?Aktion=ShowPDF&ProduktNr=223997&Ausgabe=228460&ArtikelNr=63555 Relationship between Salt Intake, Nitric Oxide and Asymmetric Dimethylarginine and Its Relevance to Patients with End-Stage]</ref><ref>{{Cite journal |first=David A. |last=McCarron |title=Dietary sodium and cardiovascular and renal disease risk factors: dark horse or phantom entry? |journal=Nephrol Dial Transplant |year=2008 |volume=23 |issue=7 |pages=2133–2137 |doi=10.1093/ndt/gfn312 |pmid=18587159 |pmc=2441768 |postscript=<!--None-->}}.</ref>

==Crystal structure==
[[Image:NaCl polyhedra.png|thumb|The crystal structure of sodium chloride. Each ion has six nearest neighbors, with [[octahedral geometry]].]]
[[Image:Close Up View Of Sodium Chloride Crystals.jpg|thumb|Close up view of NaCl crystals]]
{{main|Cubic crystal system}}
Sodium chloride forms [[crystal]]s with face-centered cubic [[symmetry]]. In these, the larger [[Chlorine|chloride]] [[ion]]s, shown to the right as green spheres, are arranged in a cubic [[close-packing]], while the smaller [[sodium]] ions, shown to the right as silver spheres, fill all the cubic gaps between them. Each ion is surrounded by six ions of the other kind; the surrounding ions are located at the vertices of a regular [[octahedron]]. 

This same basic structure is found in many other [[mineral]]s and is commonly known as the [[halite]] or rock-salt crystal structure. It can be represented as a face-centered cubic (fcc) lattice with a two atom basis. The first atom is located at each lattice point, and the second atom is located half way between lattice points along the fcc unit cell edge.

It is held together by an [[ionic bond]] which is produced by [[electrostatic force]]s arising from the difference in charge between the ions.

==Road salt==
While salt was once a scarce commodity in history, industrialized production has now made salt plentiful. Approximately 51% of world output is now used by cold countries to [[deicing|de-ice]] roads in winter, both in [[grit bin]]s and spread by [[winter service vehicle]]s. [[Calcium chloride]] is preferred over sodium chloride, since CaCl<sub>2</sub> releases energy upon forming a solution with water, heating any ice or snow it is in contact with. It also lowers the freezing point, depending on the concentration. NaCl does not release heat upon solution; however, it does lower the freezing point. Calcium chloride is thought to be more environmentally friendly than sodium chloride when used to de-ice roads, however a drawback is that it tends to promote corrosion (of vehicles) more so than sodium chloride. NaCl is also more readily available and does not have any special handling or storage requirements, unlike calcium chloride. The salinity (S) of water is measured as grams salt per kilogram of water, and the freezing temperatures are as follows. 
{| class="wikitable"
|-
| S (g/kg)
| 0
| 15
| 30
| 45
| 59
| 75
| 90
| 106
| 123
| 140
| 157
| 175
| 193
| 212
| 231
| 250
| 269
| 290
| 311
| 331
| 353
|-
| T (°C)
| 0
| −0.8
| −1.7
| −2.7
| −3.6
| −4.6
| −5.5
| −6.6 
| −7.8
| −9.1
| −10.4
| −11.8
| −13.2
| −14.6
| −16.2
| −17.8
| −19.4
| −21.1
| −17.3
| −11.1
| −2.7
|}

===Additives===
Most table salt sold for consumption today is not pure sodium chloride. In 1911, [[magnesium carbonate]] was first added to salt to make it flow more freely.<ref>{{cite web |title=Morton Salt FAQ |url=http://www.mortonsalt.com/faqs/index.html#q3 |accessdate = 2007-05-12}}</ref> In 1924 trace amounts of [[iodine]] in form of sodium iodide, [[potassium iodide]] or [[potassium iodate]] were first added, to reduce the incidence of simple [[Goitre|goiter]].<ref>{{cite journal |author=Markel H |title="When it rains it pours": endemic goiter, iodized salt, and David Murray Cowie, MD |journal=American journal of public health |volume=77 |issue=2 |pages=219–29 |year=1987|url = http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1646845|pmid=3541654 |doi=10.2105/AJPH.77.2.219 |pmc=1646845}}</ref>

Salt for de-icing in the United Kingdom predominantly comes from a single mine in Winsford in [[Salt in Cheshire|Cheshire]]. Prior to distribution it has an anti-caking agent added: [[Sodium ferrocyanide|sodium hexacyanoferrate(II)]] at less than 100 ppm. This treatment enables rock salt to flow freely out of the gritting vehicles despite being stockpiled prior to use. In recent years this additive has also been used in table salt.

===Environmental impact===
Road salt ends up in fresh water bodies and could harm aquatic plants and animals by disrupting their [[osmoregulation]] ability.<ref>[http://www.slate.com/id/2244156 Does road salt harm the environment?]</ref> An alternative is to spread rough sand on ice so the surface is not slippery.

The omnipresence of salt posts a problem in any coastal coating application, as trapped salts cause great problems in adhesion. Costs can reach staggering amounts. Naval authorities and ship builders keep a close eye on salt concentrations on surfaces during construction. Maximum salt concentrations on surfaces are dependent on the authority and application. The [[International Maritime Organization|IMO]] regulation is mostly used and sets salt levels to a maximum of 50&nbsp;mg/m2 soluble salts measured as sodium chloride. These measurements are done by means of a [[Bresle test]].

<gallery>
Image:Dead-Sea---Salt-Evaporation-Ponds.jpg| [[Israel]]i and [[Jordan]]ian salt evaporation ponds at the south end of the [[Dead Sea]].
Image:Piles of Salt Salar de Uyuni Bolivia Luca Galuzzi 2006 a.jpg|Mounds of salt, [[Salar de Uyuni]], [[Bolivia]].
Image:Aigues-Mortes2.jpg|Evaporation lagoons, [[Aigues-Mortes]], [[France]].
</gallery>

==See also==
{{Cookbook|Salt}}
*[[Biosalinity]]
*[[Kala Namak]]
*[[Halite]], the mineral form of sodium chloride
*[[Salinity]]
*[[Salt]]
*[[Soap]]
*[[Salting the earth]]

==References==
{{reflist|2}}

==Further reading==
#Kaufmann, Dale W., ''SODIUM CHLORIDE, The Production and Properties of Salt and Brine'', ACS Monograph 145, American Chemical Society, Washington, D.C., 1960, 743 pages. Library of Congress Catalog Card Number 79-50778. 
#Kurlansky, Mark, ''SALT, A World History'', Walker and Company, New York, 2002, 484 pages. ISBN 0-8027-1373-4

==External links==
{{Commons2|Sodium chloride}}
*[http://www.saltsense.co.uk/deicing-environ01.htm The Salt Manufacturers Association] website
*[http://www.saltinstitute.org Salt Institute] website
*[http://salt.org.il/news_arch.htm Salt Archive] website
*[http://minerals.usgs.gov/minerals/pubs/commodity/salt/ Salt] [[United States Geological Survey]] Statistics and Information
*[http://www.usroads.com/journals/p/rmj/9712/rm971202.htm US Road Management] website
*[http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8800478&dopt=Abstract Salt Intake in Cold Weather]
*[http://msds.chem.ox.ac.uk/SO/sodium_chloride.html Oxford MSDS]
*[http://www.jtbaker.com/msds/englishhtml/S3338.htm JtBaker MSDS]

{{Sodium compounds}}

[[Category:Granular materials]]
[[Category:Preservatives]]
[[Category:Antiseptics]]
[[Category:Snow removal]]
[[Category:Sodium compounds]]
[[Category:Chlorides]]
[[Category:World Health Organization essential medicines]]

[[am:ጨው]]
[[ar:كلوريد الصوديوم]]
[[az:Natrium Xlorid]]
[[bn:সোডিয়াম ক্লোরাইড]]
[[bs:Natrijum hlorid]]
[[bg:Натриев хлорид]]
[[ca:Clorur de sodi]]
[[cs:Chlorid sodný]]
[[cy:Halen]]
[[da:Natriumklorid]]
[[de:Natriumchlorid]]
[[et:Naatriumkloriid]]
[[es:Cloruro de sodio]]
[[eo:Natria klorido]]
[[eu:Sodio kloruro]]
[[fa:کلرید سدیم]]
[[fr:Chlorure de sodium]]
[[gl:Cloruro de sodio]]
[[ko:염화 나트륨]]
[[hy:Նատրիումի քլորիդ]]
[[hr:Natrijev klorid]]
[[id:Natrium klorida]]
[[is:Borðsalt]]
[[it:Cloruro di sodio]]
[[he:מלח בישול]]
[[ka:ნატრიუმქლორიდი]]
[[la:Natrii chloridum]]
[[lv:Nātrija hlorīds]]
[[lt:Natrio chloridas]]
[[hu:Nátrium-klorid]]
[[ms:Natrium klorida]]
[[nl:Natriumchloride]]
[[ja:塩化ナトリウム]]
[[no:Koksalt]]
[[nds:Natriumchlorid]]
[[pl:Chlorek sodu]]
[[pt:Cloreto de sódio]]
[[qu:Yanuna kachi]]
[[ru:Хлорид натрия]]
[[scn:Cloruru di sodiu]]
[[simple:Table salt]]
[[sk:Chlorid sodný]]
[[sr:Кухињска со]]
[[sv:Natriumklorid]]
[[th:โซเดียมคลอไรด์]]
[[uk:Хлорид натрію]]
[[vi:Natri clorua]]
[[fiu-vro:Keedosuul]]
[[zh:氯化钠]]
[[Category:2Fix]]