Editing Sodium chloride (section)

==Uses==
In addition to the many familiar domestic uses of salt, more dominant applications of the approximately 250 million tonnes per year production (2008 data) include chemicals and de-icing.<ref name="Ullmann">Westphal, Gisbert ''et al.'' (2002) "Sodium Chloride" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim {{doi|10.1002/14356007.a24_317.pub4}}.</ref>

===Chemical functions===
Salt is used, directly or indirectly, in the production of many chemicals, which consume most of the world's production.<ref name=usgs/>

====Chlor-alkali industry====
{{See also|Chloralkali process}}
It is the starting point for the [[chloralkali process]], the industrial process to produce [[chlorine]] and [[sodium hydroxide]], according to the [[chemical equation]]
:<chem>2 NaCl{} + 2 H2O ->[\text{electrolysis}] Cl2{} + H2{} + 2 NaOH</chem>

This electrolysis is conducted in either a mercury cell, a diaphragm cell, or a membrane cell. Each of those uses a different method to separate the chlorine from the sodium hydroxide. Other technologies are under development due to the high energy consumption of the electrolysis, whereby small improvements in the efficiency can have large economic paybacks. Some applications of chlorine include [[PVC]] [[thermoplastic]]s production, disinfectants, and solvents.

Sodium hydroxide is extensively used in many different industries enabling production of paper, soap, aluminum, and more.

===Soda-ash industry===
Sodium chloride is used in the [[Solvay process]] to produce [[sodium carbonate]] and [[calcium chloride]]. Sodium carbonate, in turn, is used to produce [[glass]], [[sodium bicarbonate]], and [[dye]]s, as well as a myriad of other chemicals. In the [[Mannheim process]], sodium chloride is used for the production of [[sodium sulfate]] and [[hydrochloric acid]].

===Miscellaneous industrial uses===
Sodium chloride is heavily used, so even relatively minor applications can consume massive quantities. In [[crude oil|oil]] and [[natural gas|gas]] exploration, salt is an important component of drilling fluids in well drilling.<ref>{{Cite book |last1=Caenn |first1=Ryen |title=Composition and properties of drilling and completion fluids |last2=Darley |first2=H. C. H. |last3=Gray |first3=George Robert |last4=Gray |first4=George Robert |date=2011 |publisher=Gulf Professional Pub |isbn=978-0-12-383858-2 |edition=6th |location=Amsterdam ; Boston, MA}}</ref> It is used to [[flocculation|flocculate]] and increase the [[density]] of the drilling fluid to overcome high downwell gas pressures. Whenever a drill hits a salt formation, salt is added to the drilling fluid to saturate the solution in order to minimize the dissolution within the salt stratum.<ref name=Ullmann/> Salt is also used to increase the curing of concrete in cemented casings.<ref name=usgs/>

In textiles and dyeing, salt is used as a brine rinse to separate organic contaminants,<ref>{{Cite journal |last1=Partal |first1=Recep |last2=Basturk |first2=Irfan |last3=Murat Hocaoglu |first3=Selda |last4=Baban |first4=Ahmet |last5=Yilmaz |first5=Ecem |date=2022 |title=Recovery of water and reusable salt solution from reverse osmosis brine in textile industry: A case study |journal=Water Resources and Industry |language=en |volume=27 |pages=100174 |doi=10.1016/j.wri.2022.100174 |bibcode=2022WRI....2700174P |doi-access=free }}</ref> to promote "salting out" of dyestuff precipitates, and to blend with concentrated dyes to increase yield in dyebaths and make the colors look sharper. One of its main roles is to provide the positive ion charge to promote the absorption of negatively charged ions of dyes.<ref name=usgs/>

For use in the [[pulp and paper industry]], it is used to manufacture [[sodium chlorate]], which is then reacted with [[sulfuric acid]] and a reducing agent such as [[methanol]] to manufacture [[chlorine dioxide]], a [[bleach]]ing chemical that is widely used to [[Bleaching of wood pulp|bleach wood pulp]].

In tanning and leather treatment, salt is added to animal [[hide (skin)|hides]] to inhibit microbial activity on the underside of the hides and to attract moisture back into the hides.<ref name=usgs/>

In rubber manufacture, salt is used to make [[synthetic rubber|buna]], [[neoprene]], and white rubber types. Salt brine and sulfuric acid are used to coagulate an emulsified [[latex]] made from chlorinated [[butadiene]].<ref name=usgs/><ref name=Ullmann/>

Salt also is added to secure the soil and to provide firmness to the foundation on which highways are built. The salt acts to minimize the effects of shifting caused in the subsurface by changes in humidity and traffic load.<ref name=usgs/>

===Water softening===
{{main|Water softening}}
[[Hard water]] contains [[calcium]] and [[magnesium]] ions that interfere with action of [[soap]] and contribute to the buildup of a scale or film of alkaline mineral deposits in household and industrial equipment and pipes. Commercial and residential water-softening units use [[ion-exchange resin]]s to remove ions that cause the hardness. These resins are generated and regenerated using sodium chloride.<ref name=usgs/><ref name=Ullmann/>

===Road salt===
{{main|Road salt}}
The second major application of salt is for [[deicing]] and anti-icing of roads, both in [[grit bin]]s and spread by [[winter service vehicle]]s. In anticipation of snowfall, roads are optimally "anti-iced" with brine (concentrated [[solution (chemistry)|solution]] of salt in water), which prevents bonding between the snow-ice and the road surface. This procedure obviates the heavy use of salt after the snowfall. For deicing, mixtures of brine and salt are used, sometimes with additional agents such as [[calcium chloride]] and/or [[magnesium chloride]]. The use of salt or brine becomes ineffective below {{convert|−10|°C|0}}.

[[File:Winter road salt.jpg|thumbnail|left|upright=1.15|Mounds of road salt for use in winter]]
Salt for deicing in the United Kingdom predominantly comes from a single mine in [[Winsford]] in [[salt in Cheshire|Cheshire]]. Prior to distribution it is mixed with <100 ppm of [[sodium ferrocyanide]] as an [[anticaking agent]], which 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. Other additives had been used in road salt to reduce the total costs. For example, in the US, a byproduct carbohydrate solution from sugar-beet processing was mixed with rock salt and adhered to road surfaces about 40% better than loose rock salt alone. Because it stayed on the road longer, the treatment did not have to be repeated several times, saving time and money.<ref name=usgs/>

In the technical terms of physical chemistry, the minimum freezing point of a water-salt mixture is {{convert|−21.12|C|F}} for 23.31 wt% of salt. Freezing near this concentration is however so slow that the [[eutectic point]] of {{convert|−22.4|C|F}} can be reached with about 25 wt% of salt.<ref name="u1"/>

====Environmental effects====
Road salt ends up in fresh-water bodies and could harm aquatic plants and animals by disrupting their [[osmoregulation]] ability.<ref>{{cite news |last=Rastogi |first=Nina Shen |date=2010-02-16 |title=Salting the Earth |language=en-US |work=Slate |url=https://slate.com/technology/2010/02/does-road-salt-harm-the-environment.html |access-date=2023-03-11 |issn=1091-2339 |archive-date=11 March 2023 |archive-url=https://web.archive.org/web/20230311162816/https://slate.com/technology/2010/02/does-road-salt-harm-the-environment.html |url-status=live }}</ref> The omnipresence of salt in coastal areas poses a problem in any [[coating]] application, because trapped salts cause great problems in adhesion. Naval authorities and ship builders monitor the salt concentrations on surfaces during construction. Maximal 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/m<sup>2</sup> soluble salts measured as sodium chloride. These measurements are done by means of a [[Bresle test]]. Salinization (increasing salinity, aka ''[[freshwater salinization]] syndrome'') and subsequent increased metal leaching is an ongoing problem throughout North America and European fresh waterways.<ref>{{cite web |url=https://phys.org/news/2018-12-saltier-waterways-dangerous-chemical-cocktails.html |title=Saltier waterways are creating dangerous 'chemical cocktails' |website=phys.org |access-date=3 December 2018 |archive-date=3 December 2018 |archive-url=https://web.archive.org/web/20181203202733/https://phys.org/news/2018-12-saltier-waterways-dangerous-chemical-cocktails.html |url-status=live }}</ref>

In highway de-icing, salt has been associated with [[corrosion]] of bridge decks, motor vehicles, reinforcement bar and wire, and unprotected steel structures used in road construction. [[Surface runoff]], vehicle spraying, and windblown salt also affect soil, roadside vegetation, and local surface water and groundwater supplies. Although evidence of environmental loading of salt has been found during peak usage, the spring rains and thaws usually dilute the concentrations of sodium in the area where salt was applied.<ref name=usgs/> A 2009 study found that approximately 70% of the road salt being applied in the [[Minneapolis-St Paul]] metro area is retained in the local watershed.<ref>{{cite web |url=https://www.sciencedaily.com/releases/2009/02/090210125424.htm |title=Most Road Salt Is Making It into Lakes And Rivers |date=20 February 2009 |website=www.sciencedaily.com |publisher=University of Minnesota |access-date=27 September 2015 |archive-date=14 February 2009 |archive-url=https://web.archive.org/web/20090214150117/https://www.sciencedaily.com/releases/2009/02/090210125424.htm |url-status=live }}</ref>

====Substitution====
Some agencies are substituting [[beer]], [[molasses]], and [[beet]] juice instead of road salt.<ref>{{cite web |url=https://phys.org/news/2018-01-salt-solution-winter-dangers-threatens.html |author=Casey, Michael |title=Turning to beet juice and beer to address road salt danger |website=phys.org |access-date=3 December 2018 |archive-date=29 January 2018 |archive-url=https://web.archive.org/web/20180129122230/https://phys.org/news/2018-01-salt-solution-winter-dangers-threatens.html |url-status=live }}</ref> Airlines utilize more [[glycol]] and [[sugar]] rather than salt-based solutions for deicing.<ref>{{cite web |url=https://www.mro-network.com/maintenance-repair-overhaul/easa-cautions-organic-salt-deicing-fluid |title=EASA Cautions on Organic Salt Deicing Fluid |date=9 December 2016 |website=MRO Network |access-date=3 December 2018 |archive-date=10 January 2018 |archive-url=https://web.archive.org/web/20180110171604/https://www.mro-network.com/maintenance-repair-overhaul/easa-cautions-organic-salt-deicing-fluid |url-status=live }}</ref>

===Food industry and agriculture===
{{main|Salt}}
Salt is added to food, either by the food producer or by the consumer, as a flavor enhancer, preservative, binder, [[fermentation (food)|fermentation]]-control additive, texture-control agent, and color developer. The salt consumption in the food industry is subdivided, in descending order of consumption, into other food processing, meat packers, [[canning]], baking, dairy, and grain mill products. Salt is added to promote color development in bacon, ham and other processed meat products. As a preservative, salt inhibits the growth of bacteria. Salt acts as a binder in [[sausage]]s to form a binding gel made up of meat, fat, and moisture. Salt also acts as a flavor enhancer and as a [[tenderizer]].<ref name=usgs/>

It is used as a cheap and safe [[desiccant]] because of its [[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. Many [[microorganism]]s cannot live in a 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 bacon, fish, or cabbage.

In many dairy industries, salt is added to cheese as a color-, fermentation-, and texture-control agent. The dairy subsector includes companies that manufacture creamery butter, condensed and evaporated milk, frozen desserts, ice cream, natural and processed cheese, and specialty dairy products. In canning, salt is primarily added as a flavor enhancer and [[preservative]]. It also is used as a carrier for other ingredients, dehydrating agent, enzyme inhibitor and tenderizer. In baking, salt is added to control the rate of fermentation in bread dough. It also is used to strengthen the [[gluten]] (the elastic protein-water complex in certain doughs) and as a flavor enhancer, such as a topping on baked goods. The food-processing category also contains grain mill products. These products consist of milling flour and rice and manufacturing cereal breakfast food and blended or prepared flour. Salt is also used a seasoning agent in products such as potato chips, [[pretzel]]s, and cat and dog food.<ref name=usgs/>

Sodium chloride is used in veterinary medicine as [[emesis]]-causing agent. It is given as warm saturated solution. Emesis can also be caused by [[pharynx|pharyngeal]] placement of small amount of plain salt or salt crystals.

For watering plants to use sodium chloride ({{chem|Na|Cl}}) as a fertilizer, moderate concentration is used to avoid potential toxicity: {{convert|1|-|3|g}} per liter is generally safe and effective for most plants.<ref>{{cite journal|doi=10.1093/aob/mcu217|date=1 December 2014 |title=Sodium chloride toxicity and the cellular basis of salt tolerance in halophytes |last1=Flowers |first1=Timothy J. |last2=Munns |first2=Rana |last3=Colmer |first3=Timothy D. |journal=Annals of Botany |volume=115 |issue=3 |pages=419–431 |pmid=25466549 |pmc=4332607 }}</ref><ref>{{cite journal|doi=10.1093/jxb/ert326|date=22 October 2013 |title=Sodium in plants: Perception, signalling, and regulation of sodium fluxes |last1=Maathuis |first1=Frans J. M. |journal=Journal of Experimental Botany |volume=65 |issue=3 |pages=849–858 |pmid=24151301 }}</ref><ref>{{cite journal|doi=10.21273/HORTSCI.43.6.1888 |title=Sodium Chloride Effects on Growth, Morphology, and Physiology of Chrysanthemum (Chrysanthemum ×morifolium) |date=2008 |last1=Lee |first1=M. Kate |last2=Van Iersel |first2=Marc W. |journal=HortScience |volume=43 |issue=6 |pages=1888–1891 |doi-access=free }}</ref>

===Medicine===
{{Main|Saline (medicine)}}
Sodium chloride is used together with water as one of the primary solutions for [[intravenous therapy]]. [[Nasal spray]] often contains a [[saline (medicine)|saline]] solution.

Sodium chloride is also available as an oral tablet and is taken to treat low sodium levels.<ref>{{cite web |title=Sodium Chloride for oral solution |url=https://my.clevelandclinic.org/health/drugs/19276-sodium-chloride-tablets |website=Cleveland Clinic |access-date=March 9, 2024 |language=en |archive-date=9 March 2024 |archive-url=https://web.archive.org/web/20240309051026/https://my.clevelandclinic.org/health/drugs/19276-sodium-chloride-tablets |url-status=live }}</ref>

===Firefighting===
[[File:Metlx.jpg|thumb|upright|A class-D fire extinguisher for various metals]]
Sodium chloride is the principal extinguishing agent in dry-powder [[fire extinguisher]]s that are used on combustible metal fires, for metals such as magnesium, zirconium, titanium, and lithium (Class D extinguishers). The salt forms an oxygen-excluding crust that smothers the fire.<ref>{{cite web |last1=Bagot |first1=Keith |last2=Subbotin |first2=Nicholas |last3=Kalberer |first3=Jennifer |title=Evaluation of a New Liquid Fire-Extinguishing Agent for Combustible Metal Fires |url=http://www.tc.faa.gov/its/worldpac/techrpt/artn06-26.pdf |website=[[Federal Aviation Administration]] |publisher=[[U.S. Department of Transportation]] |date=November 2006 |access-date=1 May 2024 |archive-date=2 May 2024 |archive-url=https://web.archive.org/web/20240502071206/https://www.tc.faa.gov/its/worldpac/techrpt/artn06-26.pdf |url-status=live }}</ref>

===Cleanser===
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 toothpaste and is commonly used to deice driveways, parking lots, and walkways.

===Infrared optics===
Sodium chloride crystals have a [[transmittance]] of at least 90% (through 1&nbsp;mm) for [[infrared]] light having wavelengths in the range 0.2– 18&nbsp;[[μm]].<ref>{{cite book |last1=Waynant |first1=Ronald W. |last2=Ediger |first2=Marwood N. |title=Electro-optics Handbook |chapter=Chapter 11: Optical Materials: Visible and Infrared |publisher=McGraw-Hill Professional Publishing |publication-place=New York |date=2000 |isbn=0-07-068716-1 |url=https://citeseerx.ist.psu.edu/document?repid=rep1&type=pdf&doi=1d1e91eee8d9531a5744405441940c50d7a69dde |page=11.20 |access-date=1 May 2024 |archive-date=1 May 2024 |archive-url=https://web.archive.org/web/20240501190105/https://citeseerx.ist.psu.edu/document?repid=rep1&type=pdf&doi=1d1e91eee8d9531a5744405441940c50d7a69dde |url-status=live }}</ref> They were used in optical components such as windows and lenses, where few non-absorbing alternatives existed in that spectral range. While inexpensive, NaCl crystals are soft and [[hygroscopy|hygroscopic]] – when exposed to the water in ambient air, they gradually cover with "frost". This limits application of NaCl to dry environments, vacuum-sealed areas, or short-term uses such as prototyping. Materials that are mechanically stronger and less sensitive to moisture, such as [[zinc selenide]] and [[chalcogenide glass]]es, more widely used than NaCl.