Sodium chloride

Sodium chloride

Sodium chloride crystals in a form of halite
Crystal structure with sodium in purple and chloride in green[1]
Names
IUPAC name Sodium chloride
Other names common salt, regular salt halite, rock salt table salt, sea salt saline
Identifiers
CAS Number	7647-14-5 Y
3D model ( JSmol )	Interactive image
Beilstein Reference	3534976
ChEBI	CHEBI:26710 Y
ChEMBL	ChEMBL1200574 N
ChemSpider	5044 Y
ECHA InfoCard	100.028.726
EC Number	231-598-3
Gmelin Reference	13673
KEGG	D02056 Y
MeSH	Sodium+chloride
PubChem CID	5234
RTECS number	VZ4725000
UNII	451W47IQ8X Y
CompTox Dashboard (EPA)	DTXSID3021271
InChI InChI=1S/ClH.Na/h1H;/q;+1/p-1 Y Key: FAPWRFPIFSIZLT-UHFFFAOYSA-M Y InChI=1/ClH.Na/h1H;/q;+1/p-1 Key: FAPWRFPIFSIZLT-REWHXWOFAE
SMILES [Na+].[Cl-]
Properties
Chemical formula	NaCl
Molar mass	58.443 g/mol[2]
Appearance	Colorless cubic crystals[2]
Odor	Odorless
Density	2.17 g/cm3[2]
Melting point	800.7 °C (1,473.3 °F; 1,073.8 K)[2]
Boiling point	1,465 °C (2,669 °F; 1,738 K)[2]
Solubility in water	360 g/L (25°C)[2]
Solubility in ammonia	21.5 g/L
Solubility in methanol	14.9 g/L
Magnetic susceptibility (χ)	−30.2·10−6 cm3/mol[3]
Refractive index (nD)	1.5441 (at 589 nm)[4]
Structure[5]
Crystal structure	Face-centered cubic (see text), cF8
Space group	Fm3m (No. 225)
Lattice constant	a = 564.02 pm
Formula units (Z)	4
Coordination geometry	octahedral at Na+ octahedral at Cl−
Thermochemistry[6]
Heat capacity (C)	50.5 J/(K·mol)
Std molar entropy (S⦵298)	72.10 J/(K·mol)
Std enthalpy of formation (ΔfH⦵298)	−411.120 kJ/mol
Pharmacology
ATC code	A12CA01 (WHO) B05CB01 (WHO), B05XA03 (WHO), S01XA03 (WHO)
Hazards
NFPA 704 (fire diamond)	0 0 0
Lethal dose or concentration (LD, LC):
LD50 (median dose)	3 g/kg (oral, rats)[7]
Related compounds
Other anions	Sodium fluoride Sodium bromide Sodium iodide Sodium astatide
Other cations	Lithium chloride Potassium chloride Rubidium chloride Caesium chloride Francium chloride
Supplementary data page
Sodium chloride (data page)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

Sodium chloride

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.[9]

Chemical functions

Salt is used, directly or indirectly, in the production of many chemicals, which consume most of the world's production.^[10]

Chlor-alkali industry

It is the starting point for the chloralkali process, the industrial process to produce chlorine and sodium hydroxide, according to the chemical equation

${\displaystyle {\ce {2 NaCl + 2 H2O ->[electrolysis] Cl2 + H2 + 2 NaOH}}}$

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

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 dyes, 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

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 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.[10]

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 bleaching chemical that is widely used to bleach wood pulp.

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.^[10]

In rubber manufacture, salt is used to make buna, neoprene, and white rubber types. Salt brine and sulfuric acid are used to coagulate an emulsified latex made from chlorinated butadiene.^[10][9]

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.^[10]

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 resins to remove ions that cause the hardness. These resins are generated and regenerated using sodium chloride.^[10][9]

Road salt

The second major application of salt is for deicing and anti-icing of roads, both in grit bins and spread by winter service vehicles. In anticipation of snowfall, roads are optimally "anti-iced" with brine (concentrated 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 de-icing, 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 −10 °C (14 °F).

Salt for de-icing in the United Kingdom predominantly comes from a single mine in Winsford in 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.^[10]

In the technical terms of physical chemistry, the minimum freezing point of a water-salt mixture is −21.12 °C (−6.02 °F) for 23.31 wt% of salt. Freezing near this concentration is however so slow that the

Salt is added to food, either by the food producer or by the consumer, as a flavor enhancer, preservative, binder,

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, e.g. in potato chips, pretzels, and cat and dog food.^[10]

Sodium chloride is used in veterinary medicine as

Sodium chloride is used together with water as one of the primary solutions for intravenous therapy. Nasal spray often contains a saline solution.

Sodium chloride is also available as an oral tablet, and is taken to treat low sodium levels.^[17]

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 powder is added to the mixture, along with waterproofing (metal stearates) and anticaking agents (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 30 pounds (14 kg) portable and 350 pounds (160 kg) wheeled.^{[citation needed]}

Cleanser

Since at least

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

Solid sodium chloride has a melting point of 801 °C and liquid sodium chloride boils at 1465 °C. Atomic-resolution real-time video imaging allows visualization of the initial stage of crystal nucleation of sodium chloride.[19]

The

From cold (sub-freezing) solutions, salt crystallises with

In 2023, it was discovered that under pressure, sodium chloride can form the hydrates NaCl·8.5H₂O and NaCl·13H₂O.[23]

Aqueous solutions

The attraction between the Na⁺ and Cl⁻ ions in the solid is so strong that only highly

When dissolved in water, the sodium chloride framework disintegrates as the Na⁺ and Cl⁻ ions become surrounded by polar water molecules. These solutions consist of

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[25] in diluted solutions where the effects of ionic strength and activity coefficients are negligible.

Stoichiometric and structure variants

Common salt has a 1:1 molar ratio of sodium and chlorine. In 2013, compounds of sodium and chloride of different stoichiometries 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 and other conditions: cubic and orthorhombic NaCl₃, two-dimensional metallic tetragonal Na₃Cl and exotic hexagonal NaCl.^[27] This indicates that compounds violating chemical intuition are possible, in simple systems under non-ambient conditions.^[28]

Occurrence

Salt is found in the

• 
  Modern rock salt mine near

  Mount Morris, New York, United States
• 
  Jordanian and Israeli salt evaporation ponds at the south end of the Dead Sea.
• 
  Mounds of salt, Salar de Uyuni, Bolivia.

See also

References

•  This article incorporates public domain material from Salt (PDF). United States Geological Survey.

Cited sources

• Haynes, William M., ed. (2011).
  ISBN 978-1439855119
  .

External links

Wikimedia Commons has media related to NaCl.

Wikibooks Cookbook has a recipe/module on

• Salt

• Salt United States Geological Survey Statistics and Information
• "Using Salt and Sand for Winter Road Maintenance". Road Management Journal. December 1997. Archived from the original on 21 September 2016. Retrieved 13 February 2007.
• Calculators: surface tensions, and densities, molarities and molalities of aqueous NaCl (and other salts)
• JtBaker MSDS