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Sodium chloride , commonly known as salt (although
sea salt Sea salt is salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of Salt (chemistry), salts; salt in its natural form as a crystallinity, crystalline mineral is known as ro ...

sea salt
also contains other chemical
salt Salt is a mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure fo ...
s), is an
ionic compound structure of sodium chloride, NaCl, a typical ionic compound. The purple spheres represent sodium cations, Na+, and the green spheres represent chloride anions, Cl−. The yellow stipples show the electrostatic forces. In chemistry, an ionic compo ...
with the
chemical formula A chemical formula is a way of presenting information about the chemical proportions of s that constitute a particular or molecule, using symbols, numbers, and sometimes also other symbols, such as parentheses, dashes, brackets, commas and ...
NaCl, representing a 1:1 ratio of
sodium Sodium is a with the  Na (from Latin ''natrium'') and  11. It is a soft, silvery-white, highly reactive . Sodium is an , being in of the periodic table. Its only stable is 23Na. The free metal does not occur in nature, and must be ...

sodium
and
chloride The chloride ion An ion () is a particle In the Outline of physical science, physical sciences, a particle (or corpuscule in older texts) is a small wikt:local, localized physical body, object to which can be ascribed several physical ...

chloride
ions. With molar masses of 22.99 and 35.45 g/mol respectively, 100 g of NaCl contains 39.34 g Na and 60.66 g Cl. Sodium chloride is the
salt Salt is a mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure fo ...
most responsible for the
salinity Salinity () is the saltiness or amount of dissolved in a body of , called (see also ). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensionless and equal to ‰). Salinity is an important ...

salinity
of
seawater Seawater, or salt water, is water Water is an Inorganic compound, inorganic, Transparency and translucency, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of E ...

seawater
and of the
extracellular fluid In cell biology Cell biology (also cellular biology or cytology) is a branch of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, ...
of many
multicellular organism A multicellular organism is an organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy (biol ...
s. In its edible form of
table salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of Salt (chemistry), salts; salt in its natural form as a crystallinity, crystalline mineral is known as rock salt or halite. Sa ...

table salt
, it is commonly used as a
condiment A condiment is a sauce In , a sauce is a , , or semi- food, served on or used in preparing other s. Most sauces are not normally consumed by themselves; they add flavor, moisture, and visual appeal to a dish. ''Sauce'' is a word taken fro ...
and
food preservative Food preservation includes food processing Food processing is the transformation of agricultural products into food, or of one form of food into other forms. Food processing includes many forms of processing foods, from grinding grain A gr ...
. Large quantities of sodium chloride are used in many industrial processes, and it is a major source of sodium and
chlorine Chlorine is a chemical element with the Symbol (chemistry), symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate betw ...

chlorine
compounds used as
feedstock A raw material, also known as a feedstock, unprocessed material, or primary commodity, is a basic material that is used to produce goods In economics Economics () is the social science that studies how people interact with value; in par ...
s for further chemical syntheses. A second major application of sodium chloride is de-icing of roadways in sub-freezing weather.


Uses

In addition to the familiar domestic uses of salt, more dominant applications of the approximately 250 million tonnes per year production (2008 data) include chemicals and de-icing.Westphal, Gisbert ''et al.'' (2002) "Sodium Chloride" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim .


Chemicals production

Salt is used, directly or indirectly, in the production of many chemicals, which consume most of the world's production.


Chlor-alkali industry

It is the starting point for the
chloralkali process The chloralkali process (also chlor-alkali and chlor alkali In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, molecules and ions: their compo ...
, the industrial process to produce
chlorine Chlorine is a chemical element with the Symbol (chemistry), symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate betw ...

chlorine
and
sodium hydroxide Sodium hydroxide, also known as lye A lye is a metal hydroxide traditionally obtained by leaching wood ashes, or a strong alkali In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chem ...

sodium hydroxide
, according to the
chemical equation A chemical equation is the symbolic representation of a chemical reaction A chemical reaction is a process that leads to the chemical transformation of one set of chemical substance A chemical substance is a form of matter In classical ...
:2 NaCl + 2 H2O → Cl2 + H2 + 2 NaOH 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 Polyvinyl chloride (colloquial Colloquialism or colloquial language is the style (sociolinguistics), linguistic style used for casual communication. It is the most common functional style of speech, the idiom normally employed in conversatio ...

PVC
, disinfectants, and solvents. Sodium hydroxide enables industries that produce paper, soap, and aluminium.


Soda-ash industry

Sodium chloride is used in the
Solvay process The Solvay process or ammonia-soda process is the major industrial process for the production of (soda ash, Na2CO3). The ammonia-soda process was developed into its modern form by the Belgian chemist during the 1860s. The ingredients for this are ...

Solvay process
to produce
sodium carbonate Sodium carbonate, ·10, (also known as Natrium Carbonate, washing soda, soda ash and soda crystals) is the inorganic compound with the formula Na2CO3 and its various hydrates. All forms are white, odourless, water-soluble salts that yield modera ...

sodium carbonate
and
calcium chloride Calcium chloride is an inorganic compound, a salt with the chemical formula CaCl2. It is a white coloured crystalline solid at room temperature, and it is highly soluble in water. It can be created by neutralising hydrochloric acid with calc ...

calcium chloride
. Sodium carbonate, in turn, is used to produce
glass Glass is a non- crystalline, often transparency and translucency, transparent amorphous solid, that has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most often formed by ...

glass
,
sodium bicarbonate Sodium bicarbonate ( IUPAC name: sodium hydrogen carbonate), commonly known as baking soda or bicarbonate of soda, is a chemical compound with the formula NaHCO3. It is a salt composed of a sodium cation (Na+) and a bicarbonate anion ( HCO3 ...

sodium bicarbonate
, and
dye A dye is a color Color (American English) or colour (Commonwealth English) is the visual perception, visual perceptual Physical property, property corresponding in humans to the categories called ''blue'', ''green'', ''red'', etc. Colo ...
s, as well as a myriad of other chemicals. In the Mannheim process and in the Hargreaves process, sodium chloride is used for the production of
sodium sulfate Sodium sulfate (also known as sodium sulphate or sulfate of soda) is the inorganic compound In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compou ...

sodium sulfate
and
hydrochloric acid Hydrochloric acid +(aq) Cl−(aq) or H3O+ Cl− also known as muriatic acid, is an aqueous solution An aqueous solution is a solution Solution may refer to: * Solution (chemistry) Image:SaltInWaterSolutionLiquid.jpg, upMaking a salin ...

hydrochloric acid
.


Standard

Sodium chloride has an international standard that is created by
ASTM International ASTM International, formerly known as American Society for Testing and Materials, is an international standards organization that develops and publishes voluntary consensus technical International standard, standards for a wide range of materials ...
. The standard is named ASTM E534-13 and is the standard test methods for chemical analysis of sodium chloride. These methods listed provide procedures for analyzing sodium chloride to determine whether it is suitable for its intended use and application.


Miscellaneous industrial uses

Sodium chloride is heavily used, so even relatively minor applications can consume massive quantities. In oil and gas exploration, salt is an important component of drilling fluids in well drilling. It is used to
flocculate Flocculation, in the field of chemistry, is a process by which colloidal particles come out of Suspension (chemistry), suspension to sediment under the form of floc or flake, either spontaneously or due to the addition of a clarifying agent. The ...

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. Salt is also used to increase the curing of concrete in cemented casings. In textiles and dyeing, salt is used as a brine rinse to separate organic contaminants, to promote "salting out" of dyestuff precipitates, and to blend with concentrated dyes to standardize them. One of its main roles is to provide the positive ion charge to promote the absorption of negatively charged ions of dyes. It is also used in processing
aluminium Aluminium (aluminum in and ) is a with the  Al and  13. Aluminium has a density lower than those of other common , at approximately one third that of . It has a great affinity towards , and of on the surface when exposed to air ...

aluminium
,
beryllium Beryllium is a chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science t ...

beryllium
,
copper Copper is a chemical element with the Symbol (chemistry), symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductility, ductile metal with very high thermal conductivity, thermal and electrical conductivity. A fre ...

copper
,
steel Steel is an alloy An alloy is an admixture of metal A metal (from Ancient Greek, Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appe ...

steel
and
vanadium Vanadium is a chemical element with the Symbol (chemistry), symbol V and atomic number 23. It is a hard, silvery-grey, malleable transition metal. The elemental metal is rarely found in nature, but once isolated artificially, the formation of an ...

vanadium
. In the
pulp and paper industry frame, International Paper is the world's largest pulp and paper maker. The pulp and paper industry comprises companies that use wood Wood is a porous and fibrous structural tissue found in the Plant stem, stems and roots of trees and oth ...
, salt is used to bleach wood pulp. It also is used to make
sodium chlorate Sodium chlorate is an inorganic compound In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemic ...

sodium chlorate
, which is added along with
sulfuric acid Sulfuric acid ( and the ) or sulphuric acid (), known in antiquity as oil of vitriol, is a composed of the elements , and , with the . It is a colorless, odorless and liquid that is with water. Pure sulfuric acid does not exist naturally ...

sulfuric acid
and water to manufacture
chlorine dioxide Chlorine dioxide is a chemical compound with the formula ClO2 that exists as yellowish-green gas above 11 °C, a reddish-brown liquid between 11 °C and −59 °C, and as bright orange crystals below −59 °C. It is an oxidizi ...

chlorine dioxide
, an excellent oxygen-based
bleach Bleach is the generic name for any chemical product that is used industrially and domestically to remove color from a fabric or fiber or to clean or to remove stains in a process called bleaching. It often refers, specifically, to a dilute so ...

bleach
ing chemical. The chlorine dioxide process, which originated in Germany after World War I, is becoming more popular because of environmental pressures to reduce or eliminate chlorinated bleaching compounds. In tanning and leather treatment, salt is added to animal hides to inhibit microbial activity on the underside of the hides and to attract moisture back into the hides. In rubber manufacture, salt is used to make buna,
neoprene Neoprene (also polychloroprene) is a family of synthetic rubber A synthetic rubber is any artificial elastomer An elastomer is a polymer A polymer (; Greek ''wikt:poly-, poly-'', "many" + ''wikt:-mer, -mer'', "part") is a Chemical substan ...
and white rubber types. Salt brine and sulfuric acid are used to coagulate an emulsified
latex Latex is a stable dispersion (emulsion An emulsion is a mixture of two or more liquids that are normally Miscibility, immiscible (unmixable or unblendable) owing to liquid-liquid phase separation. Emulsions are part of a more general class o ...

latex
made from chlorinated
butadiene 1,3-Butadiene (/ˌbjuːtəˈdʌɪiːn/) is the organic compound , CH4; is among the simplest organic compounds. In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds c ...

butadiene
. 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. Sodium chloride is sometimes used as a cheap and safe
desiccant A desiccant is a hygroscopic Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption (chemistry), absorption or adsorption from the surrounding Natural environment, environment, which is usually at normal ...
because of its
hygroscopic Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption (chemistry), absorption or adsorption from the surrounding Natural environment, environment, which is usually at normal or room temperature. If water m ...
properties, making salting an effective method of
food preservation Food preservation includes food processing Food processing is the transformation of agricultural products into food Food is any substance consumed to provide Nutrient, nutritional support for an organism. Food is usually of plant, animal ...

food preservation
historically; the salt draws water out of bacteria through , keeping it from reproducing, a major source of food spoilage. Even though more effective desiccants are available, few are safe for humans to ingest.


Water softening

Hard water Hard water is water Water (chemical formula H2O) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living orga ...
contains calcium and magnesium ions that interfere with action of
soap Soap is a salt (chemistry), salt of a fatty acid used in a variety of cleansing and lubricating products. In a domestic setting, soaps are surfactants usually used for washing, bathing, and other types of housekeeping. In industrial settings, ...

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 An ion-exchange resin or ion-exchange polymer is a resin or polymer A polymer (; Greek '' poly-'', "many" + '' -mer'', "part") is a substance or material consisting of very large molecule File:Pentacene on Ni(111) STM.jpg, A scanning tu ...
s to remove the offending ions that cause the hardness. These resins are generated and regenerated using sodium chloride.


Road salt

The second major application of salt is for
de-icing De-icing is the process of removing snow Snow comprises individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further changes. It cons ...

de-icing
and anti-icing of roads, both in grit bins and spread by
winter service vehicle A winter service vehicle (WSV), or snow removal vehicle, is a vehicle specially designed or adapted to Snow removal, clear thoroughfares of ice and snow. Winter service vehicles are usually based on a dump truck chassis, with adaptations allowing ...
s. In anticipation of snowfall, roads are optimally "anti-iced" with brine (concentrated
solution Solution may refer to: * Solution (chemistry) Image:SaltInWaterSolutionLiquid.jpg, upMaking a saline water solution by dissolving Salt, table salt (sodium chloride, NaCl) in water. The salt is the solute and the water the solvent. In chemistry ...
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 de-icing, mixtures of brine and salt are used, sometimes with additional agents such as
calcium chloride Calcium chloride is an inorganic compound, a salt with the chemical formula CaCl2. It is a white coloured crystalline solid at room temperature, and it is highly soluble in water. It can be created by neutralising hydrochloric acid with calc ...

calcium chloride
and/or
magnesium chloride Magnesium chloride is the name for the chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entity, molecular entities) composed of atoms from more than one chemical element, element h ...

magnesium chloride
. The use of salt or brine becomes ineffective below . Salt for de-icing in the United Kingdom predominantly comes from a single mine in
Winsford Winsford is a town and civil parish In England, a civil parish is a type of administrative parish used for local government. It is a territorial designation which is the lowest tier of local government below districts and counties, or ...
in
Cheshire Cheshire ( ;), archaically the County Palatine of Chester, is a historic and ceremonial county in North West England, northwest England. It is bordered by Merseyside and Greater Manchester to the north, Derbyshire to the east, Staffordshire and ...
. Prior to distribution it is mixed with <100 ppm of
sodium ferrocyanide Sodium ferrocyanide is the sodium Salt (chemistry), salt of the complex (chemistry), coordination compound of formula e(CN)6−. In its Hydrate, hydrous form, Na4Fe(CN)6 (sodium ferrocyanide decahydrate), it is sometimes known as yellow prussia ...

sodium ferrocyanide
as an anti-caking 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. In the technical terms of physical chemistry, the minimum freezing point of a water-salt mixture is for 23.31 wt% of salt. Freezing near this concentration is however so slow that the
eutectic point A eutectic system ( ) from the Greek ( 'well') and ( 'melting') is a homogeneous mixture In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, mo ...
of can be reached with about 25 wt% of salt.


Environmental effects

Road salt ends up in fresh-water bodies and could harm aquatic plants and animals by disrupting their
osmoregulation Osmoregulation is the active regulation of the osmotic pressure of an organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual contiguous system that embodies the Life#Biology, ...
ability. The omnipresence of salt poses a problem in any coastal coating application, as 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 IMO regulation is mostly used and sets salt levels to a maximum of 50 mg/m2 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. In highway de-icing, salt has been associated with
corrosion Corrosion is a that converts a refined metal into a more chemically stable form such as , , or . It is the gradual destruction of materials (usually a ) by chemical and/or electrochemical reaction with their environment. is the field dedica ...

corrosion
of bridge decks, motor vehicles, reinforcement bar and wire, and unprotected steel structures used in road construction. Surface runoff, vehicle spraying, and windblown actions 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. 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.


Substitution

Some agencies are substituting beer, molasses, and beet juice instead of road salt. Airlines utilize more
glycol A diol is a containing two s (−OH groups). An diol is also called a glycol. This pairing of functional groups is pervasive, and many subcategories have been identified. The most common industrial diol is . Examples of diols in which the hydr ...
and
sugar Sugar is the generic name for sweet-tasting, soluble carbohydrate is a disaccharide A disaccharide (also called a double sugar or ''biose'') is the sugar formed when two monosaccharides are joined by glycosidic linkage. Like monosacc ...

sugar
rather than salt based solutions for
de-icing De-icing is the process of removing snow Snow comprises individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further changes. It cons ...

de-icing
.


Food industry and agriculture

Many
microorganism A microorganism, or microbe,, ''mikros'', "small") and ''organism In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes ...
s cannot live in a salty environment: water is drawn out of their
cells Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Closed spaces * Monastic cell, a small room, hut, or cave in which a monk or religious recluse lives * Prison cell, a room used to hold peopl ...
by
osmosis Osmosis (, ) is the spontaneous net movement or diffusion File:DiffusionMicroMacro.gif, 250px, Diffusion from a microscopic and macroscopic point of view. Initially, there are solute molecules on the left side of a barrier (purple line) an ...

osmosis
. For this reason salt is used to some foods, such as bacon, fish, or cabbage. Salt is added to food, either by the food producer or by the consumer, as a flavor enhancer, preservative, binder,
fermentation Fermentation is a metabolism, metabolic process that produces chemical changes in organic Substrate (chemistry), substrates through the action of enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in ...
-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 Canning is a method of in which the food contents are processed and sealed in an airtight container (s like s, and ). Canning provides a that typically ranges from one to five years, although under specific circumstances, it can be muc ...

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 A sausage is a type of product usually made from , often pork, beef, or poultry, along with salt, spices and other flavourings. Other ingredients such as grains or breadcrumbs may be included as fillers or extenders. The word ''sausage' ...

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. 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 A preservative is a substance or a chemical that is added to products such as food products, beverages, pharmaceutical drugs A medication (also referred to as medicine, pharmaceutical drug, medicinal drug or simply drug) is a drug File:A ...
. 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 Gluten is a protein naturally found in some grains including wheat, barley, and rye. Although, strictly speaking, "gluten" pertains only to wheat proteins, in the medical literature it refers to the combination of prolamin and glutelin proteins ...

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, e.g. in potato chips,
pretzel A pretzel (), from dialectal German pronunciation, standard german: Breze(l) ( and French language, French / Alsatian dialect, Alsatian: ''Bretzel'') is a type of baking, baked pastry made from dough that is commonly shaped into a knot. The tradi ...

pretzel
s, cat and dog food. Sodium chloride is used in veterinary medicine as
emesis Vomiting (also known as emesis and throwing up) is the involuntary, forceful expulsion of the contents of one's stomach The stomach is a muscular, in the of humans and many other animals, including several s. The stomach has a dilat ...
-causing agent. It is given as warm saturated solution. Emesis can also be caused by placement of small amount of plain salt or salt crystals.


Medicine

Sodium chloride is used together with water as one of the primary solutions for
intravenous therapy Intravenous therapy (abbreviated as IV therapy) is a medical technique that delivers fluids, medications and nutrition directly into a person's vein Veins are blood vessels The blood vessels are the components of the circulatory system ...
.
Nasal spray Nasal sprays are used to deliver medications locally in the nasal cavities or systemically. They are used locally for conditions such as nasal congestion Nasal congestion is the blockage of nasal breathing usually due to membranes lining the ...

Nasal spray
often contains a saline solution.


Firefighting

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 A thermoplastic, or thermosoft plastic, is a plastic polymer A polymer (; Greek ''wikt:poly-, poly-'', "many" + ''wikt:-mer, -mer'', "part") is a Chemical substance, substance or material consisting of very large molecules, or macromolecules, ...
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 as a cartridge-operated unit, although stored pressure versions are now popular. Common sizes are portable and wheeled.


Cleanser

Since at least
medieval In the history of Europe The history of Europe concerns itself with the discovery and collection, the study, organization and presentation and the interpretation of past events and affairs of the people of Europe since the beginning of ...

medieval
times, people have used salt as a cleansing agent rubbed on household surfaces. It is also used in many brands of
shampoo Shampoo () is a product, typically in the form of a liquid, that is used for cleaning . Less commonly, shampoo is available in bar form, like a bar of soap. Shampoo is used by applying it to wet hair, massaging the product into the scalp, an ...

shampoo
, toothpaste and popularly to de-ice driveways and patches of ice.


Optical usage

Defect-free NaCl crystals have an optical transmittance of about 90% for infrared light, specifically between 200  nm and 20  µm. They were therefore used in optical components (windows and prisms) operating in that spectral range, where few non-absorbing alternatives exist and where requirements for absence of microscopic inhomogeneities are less strict than in the visible range. While inexpensive, NaCl crystals are soft and
hygroscopic Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption (chemistry), absorption or adsorption from the surrounding Natural environment, environment, which is usually at normal or room temperature. If water m ...
– when exposed to the ambient air, they gradually cover with "frost". This limits application of NaCl to dry environments, vacuum sealed assembly areas or for short-term uses such as prototyping. Nowadays materials like
zinc selenide Zinc selenide (Zinc, ZnSe) is a light-yellow, solid compound comprising zinc (Zn) and selenium (Se). It is an intrinsic semiconductor with a band gap of about 2.70 Electron volts, eV at . ZnSe rarely occurs in nature, and is found in the miner ...

zinc selenide
(ZnSe), which are stronger mechanically and are less sensitive to moisture, are used instead of NaCl for the infrared spectral range.


Chemistry


Solid sodium chloride

In solid sodium chloride, each ion is surrounded by six ions of the opposite charge as expected on electrostatic grounds. The surrounding ions are located at the vertices of a regular
octahedron In geometry, an octahedron (plural: octahedra, octahedrons) is a polyhedron with eight faces, twelve edges, and six vertices. The term is most commonly used to refer to the regular octahedron, a Platonic solid composed of eight equilateral tri ...

octahedron
. In the language of
close-packing In geometry Geometry (from the grc, γεωμετρία; ''wikt:γῆ, geo-'' "earth", ''wikt:μέτρον, -metron'' "measurement") is, with arithmetic, one of the oldest branches of mathematics. It is concerned with properties of space that ...
, the larger
chloride The chloride ion An ion () is a particle In the Outline of physical science, physical sciences, a particle (or corpuscule in older texts) is a small wikt:local, localized physical body, object to which can be ascribed several physical ...

chloride
ion An ion () is an atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ...
s (167 pm in size) are arranged in a cubic array whereas the smaller
sodium Sodium is a with the  Na (from Latin ''natrium'') and  11. It is a soft, silvery-white, highly reactive . Sodium is an , being in of the periodic table. Its only stable is 23Na. The free metal does not occur in nature, and must be ...

sodium
ions (116 pm) fill all the cubic gaps (octahedral voids) between them. This same basic structure is found in many other
compounds Compound may refer to: Architecture and built environments * Compound (enclosure), a cluster of buildings having a shared purpose, usually inside a fence or wall ** Compound (fortification), a version of the above fortified with defensive structu ...
and is commonly known as the
halite Halite (), commonly known as rock salt, is a type of salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of Salt (chemistry), salts; salt in its natural form as a crysta ...

halite
or rock-salt crystal structure. It can be represented as a
face-centered cubic 200px, A network model of a primitive cubic system In crystallography Crystallography is the experimental science of determining the arrangement of atoms in crystalline solids (see crystal structure). The word "crystallography" is derived fro ...
(fcc) lattice with a two-atom basis or as two interpenetrating face centered cubic lattices. The first atom is located at each lattice point, and the second atom is located halfway between lattice points along the fcc unit cell edge. Solid sodium chloride has a melting point of 801 °C.
Thermal conductivity The thermal conductivity of a material is a measure of its ability to conduct heat. It is commonly denoted by k, \lambda, or \kappa. Heat transfer occurs at a lower rate in materials of low thermal conductivity than in materials of high thermal ...

Thermal conductivity
of sodium chloride as a function of temperature has a maximum of 2.03 W/(cm K) at and decreases to 0.069 at . It also decreases with
doping Doping may refer to: * Doping, adding a dopant to something * Doping (semiconductor), intentionally introducing impurities into an extremely pure semiconductor to change its electrical properties * Aircraft dope, a lacquer that is applied to fabric ...
. Atomic-resolution real-time video imaging allows visualization of the initial stage of crystal nucleation of sodium chloride.


Aqueous solutions

The attraction between the Na+ and Cl ions in the solid is so strong that only highly polar solvents like water dissolve NaCl well. When dissolved in water, the sodium chloride framework disintegrates as the Na+ and Cl ions become surrounded by the polar water molecules. These solutions consist of
metal aquo complexMetal aquo complexes are coordination compound A coordination complex consists of a central atom or ion, which is usually metallic and is called the ''coordination centre'', and a surrounding array of bound molecules or ions, that are in turn k ...
with the formula a(H2O)8sup>+, with the Na–O distance of 250  pm. The chloride ions are also strongly solvated, each being surrounded by an average of 6 molecules of water.Lincoln, S. F.; Richens, D. T. and Sykes, A. G. (2003) "Metal Aqua Ions" Comprehensive Coordination Chemistry II Volume 1, pp. 515–555. . Solutions of sodium chloride have very different properties from pure water. The freezing point is for 23.31% mass fraction of salt, and the boiling point of saturated salt solution is near .Elvers, B. ''et al.'' (ed.) (1991) ''Ullmann's Encyclopedia of Industrial Chemistry'', 5th ed. Vol. A24, Wiley, p. 319, . From cold solutions, salt crystallises as the
dihydrate In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, molecules and ions: their composition, structure, properties, behavior and the changes they under ...
NaCl·2H2O.


pH of sodium chloride solutions

The pH of a sodium chloride solution remains ≈7 due to the extremely weak basicity of the Cl ion, which is the conjugate base of the strong acid HCl. In other words, NaCl has no effect on system pH in diluted solutions where the effects of ionic strength and activity coefficients are negligible.


Unexpected stable stoichiometric variants

Common salt has a 1:1 molar ratio of sodium and chlorine. In 2013, compounds of sodium and chloride of different
stoichiometries Stoichiometry is the calculation of reactants and Product (chemistry), products in chemical reactions in chemistry. Stoichiometry is founded on the law of conservation of mass where the total mass of the reactants equals the total mass of the ...
have been discovered; five new compounds were predicted (e.g., Na3Cl, Na2Cl, Na3Cl2, NaCl3, and NaCl7). The existence of some of them has been experimentally confirmed at high pressures: cubic and orthorhombic NaCl3 and two-dimensional metallic tetragonal Na3Cl. This indicates that compounds violating chemical intuition are possible, in simple systems under nonambient conditions.


Occurrence

Small particles of
sea salt Sea salt is salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of Salt (chemistry), salts; salt in its natural form as a crystallinity, crystalline mineral is known as ro ...

sea salt
are the dominant
cloud condensation nuclei Cloud condensation nuclei or CCNs (also known as cloud seeds) are small particles typically 0.2 µm, or 1/100 the size of a cloud In meteorology Meteorology is a branch of the atmospheric sciences which includes atmospheric chemistry a ...
far out at sea, which allow the formation of
cloud In meteorology, a cloud is an aerosol consisting of a visible mass of minute liquid drop (liquid), droplets, ice crystals, frozen crystals, or other particulates, particles suspended in the atmosphere of a planetary body or similar space. Wate ...

cloud
s in otherwise
air File:Atmosphere gas proportions.svg, Composition of Earth's atmosphere by volume, excluding water vapor. Lower pie represents trace gases that together compose about 0.043391% of the atmosphere (0.04402961% at April 2019 concentration ). Number ...

air
.


Production

Salt is currently
mass-produced Mass production, also known as flow production or continuous production, is the production of substantial amounts of standardized Standardization or standardisation is the process of implementing and developing technical standard A technic ...
by
evaporation Evaporation is a type of that occurs on the of a as it changes into the gas phase. The surrounding gas must not be saturated with the evaporating substance. When the molecules of the liquid collide, they transfer energy to each other bas ...

evaporation
of
seawater Seawater, or salt water, is water Water is an Inorganic compound, inorganic, Transparency and translucency, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of E ...

seawater
or
brine Brine is a high-concentration solution Solution may refer to: * Solution (chemistry) Image:SaltInWaterSolutionLiquid.jpg, upMaking a saline water solution by dissolving Salt, table salt (sodium chloride, NaCl) in water. The salt is the solu ...

brine
from brine wells and
salt lakes A salt lake or saline lake is a landlocked body of water ( Lysefjord) in Norway Norway ( nb, ; nn, ; se, Norga; smj, Vuodna; sma, Nöörje), officially the Kingdom of Norway, is a Nordic countries, Nordic country in Northern ...
.
Mining Mining is the extraction of valuable mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occu ...
of rock salt is also a major source. China is the world's main supplier of salt.Kostick, Dennis S. (October 2010
"Salt"
in ''U.S. Geological Survey, 2008 Minerals Yearbook''
In 2017, world production was estimated at 280 million
tonne The tonne ( or ; symbol: t) is a metric unit of mass equal to 1,000 kilogram The kilogram (also kilogramme) is the base unit of mass Mass is the physical quantity, quantity of ''matter'' in a physical body. It is also a meas ...
s, the top five producers (in million tonnes) being China (68.0), United States (43.0), India (26.0), Germany (13.0), and Canada (13.0).Salt
U.S. Geological Survey
Salt is also a byproduct of
potassium Potassium is a chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science ...

potassium
mining. File:Salt mine 0096.jpg, Modern rock salt mine near Mount Morris,
New York New York most commonly refers to: * New York City, the most populous city in the United States, located in the state of New York * New York (state), a state in the northeastern United States New York may also refer to: Film and television * New ...
,
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...

United States
File:Dead-Sea---Salt-Evaporation-Ponds.jpg,
Jordan Jordan ( ar, الأردن; tr. ' ), officially the Hashemite Kingdom of Jordan,; tr. ') is a country in Western Asia Western Asia, also West Asia, is the westernmost subregion of Asia. It is entirely a part of the Greater Middle East. It in ...

Jordan
ian and
Israel Israel (; he, יִשְׂרָאֵל, translit=Yīsrāʾēl; ar, إِسْرَائِيل, translit=ʾIsrāʾīl), officially the State of Israel ( he, מְדִינַת יִשְׂרָאֵל, label=none, translit=Medīnat Yīsrāʾēl; ), is a ...

Israel
i salt evaporation ponds at the south end of the
Dead Sea The Dead Sea ( he, יָם הַמֶּלַח lit. Sea of Salt; ar, البحر الميت , lit. ''the Dead Sea'',The first article ''al-'' is unnecessary and usually not used. or Buhayrat, Bahret or Birket Lut, ''lit.'' "Lake/Sea of Lot") is a s ...

Dead Sea
. File:Piles of Salt Salar de Uyuni Bolivia Luca Galuzzi 2006 a.jpg, Mounds of salt,
Salar de Uyuni Salar de Uyuni (or "Salar de Tunupa") is the world's largest Salt pan (geology), salt flat, or Dry lake, playa, at over in area. It is in the Daniel Campos Province in Potosí Department, Potosí in southwest Bolivia, near the crest of the Ande ...

Salar de Uyuni
,
Bolivia Bolivia ; ay, Wuliwya ; : ''Puliwya'' , officially the Plurinational State of Bolivia, is a located in western-central . The constitutional capital is , while the and executive capital is . The largest city and principal industrial ce ...

Bolivia
.


See also

* Biosalinity * *
Halite Halite (), commonly known as rock salt, is a type of salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of Salt (chemistry), salts; salt in its natural form as a crysta ...

Halite
, the mineral form of sodium chloride *
Health effects of salt Health is a state of physical, mental and social well-being Well-being, also known as ''wellness'', ''prudential value'' or ''quality of life'', refers to what is intrinsically valuable relative ''to'' someone. So the well-being of a person ...
*
Salinity Salinity () is the saltiness or amount of dissolved in a body of , called (see also ). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensionless and equal to ‰). Salinity is an important ...

Salinity
*
Salting the earth Salting the earth, or sowing with salt, is the ritual of spreading salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of Salt (chemistry), salts; salt in its natural form ...
* Salt poisoning


References

*


Cited sources

*


External links


Salt
United States Geological Survey The United States Geological Survey, abbreviated USGS and formerly simply known as the Geological Survey, is a scientific government agency, agency of the Federal government of the United States, United States government. The scientists of the ...
Statistics and Information * * Calculators
surface tensions
an
densities, molarities and molalities
of aqueous NaCl (and other salts)

{{DEFAULTSORT:Sodium Chloride Alkali metal chlorides Chlorides Household chemicals Metal halides Sodium compounds Sodium minerals Rock salt crystal structure