It is safe to say that at least one chemical compound in a fairly pure form is available in every home, in every family.This - table salt or as it is called chemical - sodium chloride, NaCl. It is known that, leaving the taiga shelter for casual travelers hunters will certainly leave matches and salt. Table salt is essential for the functioning of the body of humans and animals. Lack of salt leads to functional and organic disorders: there may be spasms of smooth muscles, sometimes affects the nervous system centers. Prolonged fasting salt can lead to death of the organism. The daily requirement for an adult salt is 10 ... 15 In hot climates, the need for salt is increased to 25 ... 30 g This is due to the fact that the sodium chloride is eliminated from the body and then to the recovery of losses in the body You need to enter more salt. When working in hot shops and in the dry and hot weather, doctors recommend drinking salted water (0.3 ... 0.5% saline solution), since the salt helps retain water in the tissues.
If you do not give the animal food, then after a while it will die of exhaustion. If the animal feed without limitation, but the desalted food, it will die quickly. The fact that the salt is a source of salt formation in the stomach (hydrochloric acid), which is part of the gastric juice. The daily amount of gastric juice adult reaches 2 liters. Its acidity characterized by a pH of 1.5 ... 2.0.
At low acidity doctors prescribe the patient a weak aqueous solution of hydrochloric (hydrochloric acid), and when he feels acidity heartburn and it is recommended to take baking soda. It neutralizes the excess acid in accordance with the equation
HCl + NaHCO 3 = NaCl + CO 2 + H 2 O
Dietary proteins entering the stomach by the enzyme (biocatalyst) pepsin split into separate components or blocks of amino acids of these amino acids. Of these synthesized protein specific to the organism. The enzyme pepsin is derived from another enzyme - pepsinogen. For conversion of pepsinogen to pepsin is necessary hydrochloric acid. With its lack of gastric juice digestion and assimilation of proteins does not occur, or is to a small extent. Hydrochloric acid is also involved in the formation of the hormone secretin and other hormones that stimulate the activity of the pancreas. Furthermore, it facilitates the transition of the food mass in the stomach and duodenum neutralization microbes from entering the stomach environment.
However, sodium chloride is needed in humans or animals, not only for the formation of hydrochloric acid in gastric juice. This salt is included in the tissue fluid and the blood. In its final concentration is 0.5 ... 0.6%.
NaCl aqueous solution are used in medicine as blood fluids after bleeding and shock events. Reducing the NaCl content in the blood plasma lead to metabolic disorders in the body.
Not receiving externally NaCl organism sends it from the blood and tissues.
Sodium chloride promotes water retention, which in turn leads to increased blood pressure. Therefore, hypertension, obesity, edema, doctors recommend reducing daily salt intake. Excess body NaCl can cause acute poisoning and lead to paralysis of the nervous system.
The human body responds quickly to the appearance of a violation of the salt balance in muscle weakness, fatigue, loss of appetite, the emergence of an unquenchable thirst.
Table salt has though weak, but the antiseptic properties. The development of putrefactive bacteria ceases only when its content 10 ... 15%. This property is widely used in the food industry and in the preservation of foods in the home.
It is difficult to imagine that in the past, in many countries salt served as a significant source of replenishment of the treasury, it has been an important subject of trade. Because of salt were bloody wars between neighboring peoples, but because of the exorbitant taxes imposed on salt, there were popular uprisings (salt riots). For example, a riot took place in Moscow in the spring of 1648 this was the increased tax on salt imposed by Tsar Alexei Mikhailovich. This rebellion ended safely. The government, fearful of unrest sweep (Moscow riot spread to Solvychegodsk, Great Ustyug, Solikamsk), reduced the level of tax. Many popular unrest in China, other Asian countries, Europe ended less happily.
In some countries, salt perform even the role of the monetary unit. Venetian traveler Marco Polo, who visited China in 1286, described the use there coins from salt crystals. The special distribution of the monetary unit of the salt obtained in many parts of Central Africa. In Ethiopia, the standard bars of rock salt were in use as currency in the XIX century. Numerous historical documents show that the Roman soldiers, and then the Crusaders are often paid salaries salt. Scientists believe that, perhaps, this is due the origin of the French word "Saler" (salary) and the Italian "soldi" (small coin).
The body of primitive man received the necessary salt with food of animal origin. However, the needs of the body was forced to seek it in a more concentrated form. For a long time it was discovered that some plants have a pleasant salty taste.These plants were dried, and then burned in a fire. The resulting ash is used as a seasoning for food.
Later, people learned to water in the fire burning pieces of wood with salt water from the sea or a lake, and the remaining ash is also used in food.
Already two thousand years BC Chinese learned how to get table salt by evaporating sea water. A method for recovering the salt from sea water by evaporation was invented independently and in various other countries. At first he appeared in countries with dry and hot climate - in India, Greece, Rome. Later, in a way become a salt mine in France, Spain, in the Crimea. In the north of our country sea water evaporated (boiled) in large vats, and served as a source of energy wood.However, in northern areas, particularly on the shores of the White Sea, it was a significant improvement method for extracting salt from sea water.
Pomors have long noticed that the freezing of sea water ice turns unsalted, while the remaining unfrozen water is much saltier. Melting ice, you can get fresh water from the sea and from the brine digested table salt with less energy consumption.
Everyone who tasted seawater, remember that it has a bitter taste, and bears little resemblance to an aqueous solution of sodium chloride. This means that seawater addition of sodium chloride containing other salts. Again, who ever be on different seas, remember that taste, density of irritation to the eyes of water are different, and therefore, they have a different composition. However, the average content (wt. Fraction,%) in sea water salts as follows: NaCl - 77,8, MgCl 2 - 10,9, MgSO 4 - 4,7, KC1, K 2 SO 4 - 2.5 , CaCO 3 , Ca (HCO 3 ) 2 - 0.3, other salts - 0.2.
In the evaporation of sea water at temperatures of 20 ... 35 ° C, first allocated the least soluble salts - carbonates of calcium, magnesium, and calcium sulfate. Then fall more soluble salts - sodium sulfate and magnesium chlorides, sodium, potassium, magnesium and after potassium and magnesium sulfates. Procedure for salt crystallization and precipitation formed composition can vary somewhat depending on temperature, evaporation rate, and other conditions. In the evaporation of sea water under natural conditions in a consistent manner the following minerals:
Calcite CaCO 3
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Magnesite MgCO 3
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Dolomite MgCO 3 · CaCO 3
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Neksvegonit MgCO 3 · 3H 2 O
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Gypsum CaSO 4 · 2H 2 O
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Anhydrite CaSO 4
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Glauber Na 2 SO 4 · CaSO 4
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Thenardier Na 2 SO 4
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Mirabilite Na 2 SO 4 · 10H 2 O
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Astrakhan Na 2 SO 4 · MgSO 4 · 4H 2 O
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Halite NaCl
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Sylvite KCl
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Carnallite KCl · MgCl 2 · 6H 2 O
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Epsom MgSO 4 · 7H 2 O
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Hexahydro MgSO 4 · 6H 2 O and other magnesium sulfate
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Cainite KCl · MgSO 4 · 3H 2 O
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Bishofit MgCl 2 · 6H 2 O
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Despite the fact that this list of minerals big, it should be remembered that the majority belongs to the sodium chloride. When cooking salt brine evaporation is not carried out to dryness and the remaining rich magnesium salts solution is discarded.
Bitter taste is caused by the sea carts magnesium salts.
Many people know that salt, located in the humid air, dampen.
Pure sodium chloride - non-hygroscopic substance, ie It does not attract moisture. Hygroscopic chlorides of magnesium and calcium. These impurities are almost always contained in the salt and because they are absorbed moisture.
In inland areas, sometimes there are underground salt springs. People have long used them for digestion of salt. In our country already since the rule of the Tatar khan Batu and his descendants salt extracted from the lakes of the Lower Volga region, with dry and hot climate. In the constellation of salt lakes in the area stand out lake Elton and Baskunchak.Commercial operation lake Elton made a century and a half. Freshly salt in many geological periods transformed into sedimentary rock - a monolith of rock salt. Painting and transparency of the latter depends on the nature of the impurities.
Studies have shown the lake Elton that his bottom stratum consists of two thick layers of rock salt, separated by a layer of clay. The thickness of the lower layer in the average is 14.4 m, and the upper lining the bottom - 18.25 m. This layer extends over 150 km 2 .
Lake Elton has a large supply of salt, but even more of the rich salt lake Baskunchak, which is currently the main source of raw materials in the Lower Volga.
The Earth's crust are quite common rock salt formations. It is believed that they were obtained as a result of crustal deformation with layers of sedimentary rock, formed by the evaporation of sea water or salt water lakes. Rock salt is squeezed at strains up to form a solid salt domes usually have a rounded shape in the plan and up to several kilometers in diameter. One such long-explored deposits of rock salt are located near Iletsk the Orenburg region. Salt dome of the deposit extends over 2 km long, 1 km wide and goes deep into the well of 1 km.
In the Perm region operated richest deposit of sylvinite. This salt rock consisting of NaCl and KCl. With its processing as fertilizer extracted KC1, a NaCl is a waste. By simply washing with water (KCl dissolves better than NaCl) receive technical salt with 98% content.
Table salt is the major raw material of the chemical industry. Obtained therefrom soda, chlorine, hydrochloric acid, sodium hydroxide, sodium metal.
In the study of the properties of the soil, scientists have found that being soaked with sodium chloride, they do not pass water. This discovery was used in the construction of irrigation canals and reservoirs. If the bottom of the reservoir cover layer land impregnated NaCl, then water leakage does not occur. For this purpose, of course, apply technical salt. Builders use sodium chloride to remove the freezing winter of land and turn it into a hard stone. To this end, areas of soil, which is planned to take out in the fall heavily sprinkled with NaCl. In this case, severe frosts data plots remain soft.
Chemists are well aware that by mixing finely ground ice with common salt can be obtained efficiently cooled mixture.For example, the composition of the mixture was 30 g NaCl per 100 g ice cooled to - 20 ° C. This is because the aqueous salt solution freezes at low temperatures. Therefore, the ice having a temperature of about 0 ° C, will melt in such a solution, taking heat from the surrounding environment. This property is a mixture of ice and salt can be successfully used as housewives. source nt.ru
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