The sodium chloride is a chemical Composé of formula Na Cl. It is called more commonly Sel of table. It is the principal product dissolves in sea water; it is also called sea salt .

It is obtained:

• in Saltworks by evaporation of the Sea water.
• in mines, by extraction of the Rock salt (Halite).

The sodium chloride is used in chemical industry to produce Chlore, caustic Soda and Hydrogène.

Chemical structure

Salt is an assembly of Ion S $Na^+$ and $Cl^-$ of cubic mesh. Salt is a Cristal, because it has the atoms forming a structure symmetrical Périodique and .

The structure of salt can be described by the contents of its mesh. A salt mesh is a cube which contains:

• an atom of Chlorine at the tops of the mesh (8 tops each one divided among 8 close meshs)
• three chlorine atoms in the center of the faces of the mesh (6 faces each one divided between 2 close meshs)
• an atom of Sodium in the center of the mesh
• three atoms sodium on the medium of the edges of the mesh (12 edges each one divided among 4 close meshs).

The structure of salt corresponds to the filling by the cations $Na^+$ of a structure host composed by the anions $Cl^-$. Indeed, the anions $Cl^-$ form under network Cubique with centered faces in which the cations $Na^+$ occupy all the octahedral sites of the mesh. In the structure of salt, the ions $Na^+$ and $Cl^-$ are interchangeable. It is as possible to say as the cations $Na^+$ form under cubic lattice with centered face in which the anions $Cl^-$ occupy all the octahedral sites of the mesh.

The structure NaCl corresponds to two pennies cubic networks with centered face of ions, shifted half of with dimensions of the mesh according to one of the directions of with dimensions of the mesh.

The Coordinence is the number of closer close atoms in the structure. All the ions $Na^+$ and $Cl^-$ have each one in salt a co-ordination number 6, i.e. any ion $Cl^-$ is surrounded by 6 ions $Na^+$ forming a Octaèdre around the $Cl^-$. And vice versa, around each ion $Na^+$ are like closer neighbors 6 ions $Cl^-$ also forming octahedral.

Natural reserve

The salt or sodium chloride is available in quasi-unlimited quantity. Indeed, there exist two types of reserves: the Rock salt or the salt dissolved in sea water. The oldest salt deposits formed in the oceans are evaluated with more than 600 million years. It is one of most abundant minerals of planet.

The Sea and the Océan S are the largest dissolved salt reserves. They are estimated at approximately 50 Quadrillion S. the sea water contains approximately 30 to 40 grams of salt per liter of water, which represents a 75 meters height distributed out of the three quarter of the surface of the Globe.

Extraction of salt

There exist several ways of recovering sodium chloride. In the countries where the sunning and the temperatures are sufficient, salt can be extracted by evaporation thanks to the system the saline Marais. A series of not very deep basins make it possible to support the evaporation of water. Salt is more and more concentrated progressively passage of sea water in the basins. In the last basins, salt forms a deposit and can be collected by scraping.

In the cold countries, the system of congelation is used. The sea water is frozen and salt forms a deposit in the increasingly concentrated brine. When the concentration is sufficient, salt ends up precipitating.

For the Halite, salt is extracted as an ore in a underground mine if the layer is sufficiently thick. But in the majority of the cases, salt is mixed or it layer is too fine. Also, to extract it, of water is injected and the salt solution is pumped on the surface.

Biological importance

In our organization, the ions $Na^+$ play a big role in the transmission of nervous flow. Salt also contributes to the maintenance of an osmotic medium favorable for the cell S and avoids the Déshydratation.

Cardiovascular risks associated with a containing soda overconsumption

In too great amount, salt contributes to increase the arterial tension. A contribution of 2 G per day would be sufficient, but consumption is in general much higher than this minimum (9 to 10 g/jour on average in 2001 in France). The salt excess would be responsible, according to work of the professor Pierre Meneton, researcher with the Inserm, of 25.000 deaths per annum in France and 75.000 cardiovascular accidents, by Hypertension.

The French Agence of public health of the food (AFSSA) recommended (January 2002) to reduce by 20% in 5 years the salt contribution in the food, to limit the average salt contribution to 7 to 8 g/jour and per capita, against 9 to 10 g/jour on average, even much more: 15% of the French population consume more than 15 grams of salt per day (salt of table and salt already contained in food). It should be noted that the most significant part of the containing soda contributions in the developed countries is in prepared food what makes essential the collaboration of food industry to try to reduce the content salt of it.

Interventionnelles studies

The majority of the studies showing an opposite relation between the quantity of introduced salt and the frequency of the cardiovascular diseases are of observational type: only is noted sodium chloride consumption of the subjects studied without trying to modify the food behavior of the latter.

The interventionnelles studies are rarer but tend to show the benefit to reduce the containing soda contribution: in Finland, the professionals passed successfully to a salt of substitution reduced in Sodium and enriched in Potassium; food the sodium ratio/potassium is indeed important. According to work of Finnish researchers of the university of Helsinki and Kuopo published in the scientific magazine " Progress in Cardiovascular Diseases" , a reduction from 30 to 35% of the salt contributions in their country, during the 30 last years, largely contributed to the fall of more than 75% of the cardiovascular Mortalité at the people of less than 65 years. In parallel the Life expectancy of the Finns increased by 6 to 7 years. Impressive benefit mainly due to a fall of more than 1 point of the blood pressure average of the population. In the same way, a reduction of almost 30% of the cardiovascular diseases was observed in another study, and this, in a way independent of the reduction of the figures tensionnels.

Production and uses

Salt is resulting from the salt-water marshes, or the mining extraction. Industrial salt is obtained by purification and bleaching, to obtain white and pure salt with 99,9%.

Artisanal salts resulting from the salt-water marshes are not bleached and do not undergo any treatment, nor addition. They are partly marketed in the form of " flower of sel".

Salt through the history

Salt was used during the Middle Ages for the salting of the meat and it is still used to this end in developing countries.

Biological uses, conservation

Salt allows during salting and of the salting to preserve food, because it allows the exudation of water out of food. This last becomes drier then and the Bactérie S will not develop, private of their water resource. Only moulds of surface can appear if salting is insufficient and if the food is not put safe from the air and the light. Salt has a bacteriostatic action starting from a concentration of 10%, but with the evolution of the food preferences, the salt concentration is about 4% in food, which obliges to preserve cold food.

The use of salt by agribusiness industry also makes it possible to absorb water of the ambient conditions, which causes to sell water with the price of the product.

One also uses salt in industry to preserve the skins of animals in order to make Cuir of it, or to preserve the Cornichon S in a mixture of vinegar, wine and salt.

Agent of sapidity

See also: food Salt

The sodium chloride makes it possible to increase the sapidity of food, savors are done more intense thanks to salt. The ions $Na^+$ stimulate the taste buds while the ions $Cl^-$ give the salted taste.

Additives

Salt makes it possible to solubilize the Protéine S known as salinosolubles. This property is used during the manufacture of boiled ham. The pieces of ham are mixed with a brine (mixture of water and salt). The proteins salinosolubles then form a mass viscous and sticking, the silt.

Once the silt is sufficiently abundant, the pieces are joined together and cooked together in a mould to give the form to the product. The silt is used then as adhesive between the blocks which, to cooking, gives a translucent gelatin, visible with the cut. The food products containing Viande contain approximately salt 4%.

Salting of the roads in winter

Salt used to salt the roads is a coarse salt. The temperature of solidification of salt water depends on the salt concentration of the solution. It is minimal (approximately -20°C) for a proportion of salt from approximately 20%, this minimum corresponds to the mixture known as " Eutectic ".

So that the sodium chloride (solid) can dissolve (in a liquid), one needs sufficient energy to break the electrostatic connections which maintain the ions Na⁺ and Cl^- in the solid form. It is an endothermic chemical reaction (3900 joules are necessary by mole of salt to dissolve it).

When one puts salt in snow, this one will dissolve by drawing energy in the snow, which becomes colder. The sodium chloride joins ice then to form a mixture of salt water (the ice in the presence of salt is not stable any more, it melts to form a mixture) having property different from pure water: the temperature necessary so that ice remains thus becomes lower than 0°C.

Separation of essential oil

The sodium chloride is used to facilitate the separation of essential oil during its extraction.

Etymology

Other facts

The labels give sodium, seldom salt; it is good to know that: 2,54 Sodium = sodium chloride = Salt

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