The salt

One can say with certainty that at least one chemical compound in a fairly pure form is available in every home. This is - table salt or as it is called by chemists - sodium chloride NaCl.

This is - table salt or as it is called by chemists - sodium chloride NaCl

It is difficult for us to imagine that in the past in many countries salt was an important source of replenishment of the treasury, it was an important subject of trade. Cooking salt caused bloody wars between neighboring nations, and because of exorbitant taxes levied on salt, there were popular uprisings.

In some countries, table salt served even as a monetary unit. Numerous historical documents indicate that the Roman soldiers, and then the crusaders, were often paid salaries.

Cooking salt is absolutely necessary for the life of the human and animal body. The lack of this salt leads to functional and organic disorders: spasms of smooth muscles may occur, and sometimes the centers of the nervous system are affected. The daily requirement for table salt of an adult is 10-15 g. In a hot climate, the need for salt rises to 25-30 g. This is due to the fact that sodium chloride is excreted from the body with sweat and to restore the loss in the body you need to inject more salt . When working in hot shops and in dry and hot climate, doctors recommend drinking salted water (0,3-0,5% solution of table salt), as the salt helps to retain water in the tissues.

Cooking salt serves as a source of formation in the stomach of hydrochloric acid, which is an integral part of gastric juice. The daily amount of gastric juice of an adult reaches 2 liters. Its acidity is characterized by a pH value of 1,5-2,0.

With reduced acidity, doctors prescribe to the patient a weak aqueous solution of hydrochloric acid, and with increased acidity, he experiences heartburn and is recommended to take baking soda. It neutralizes excess acid in accordance with the equation:

HCl+NaHCO3=NaCl+CO2+H2O

Nutritional proteins that enter the stomach are split into individual amino acids or blocks of these amino acids by the action of the enzyme (biological catalyst) pepsin. From them the protein, inherent in the given organism, is synthesized. The enzyme pepsin is formed from another enzyme - pepsinogen. Hydrochloric acid is needed to convert pepsinogen to pepsin. With its lack in gastric juice, digestion and assimilation of proteins does not occur or goes to a small extent. Hydrochloric acid also participates in the formation of the hormone secretin and some other hormones that stimulate the activity of the pancreas.

However, sodium chloride is needed by the human or animal body, not only for the formation of hydrochloric acid in gastric juice. Table salt enters the tissue fluid and the blood. In the blood, its concentration is 0,5-0,6%.

Aqueous solutions of NaCl in medicine are used as blood-substituting liquids after bleeding and during shock phenomena. Reducing the content of NaCl in the blood plasma leads to a violation of metabolism in the body.

Cooking salt helps to keep water in the body, which, in turn, leads to increased blood pressure. Therefore, for hypertension, obesity, edema, doctors recommend reducing the daily intake of table salt. Excess in the body NaCl can cause acute poisoning and lead to paralysis of the nervous system.

Already two thousand years BC the chinese learned to get salt by evaporation of sea water. The method of extracting salt from sea water by evaporation first appeared in countries with a dry and hot climate - in India, Greece, Rome. Later in this way, salt was extracted in France, Spain, and the Crimea.

Anyone who has tasted sea water, remember that it has a bitter taste and little resemblance to an aqueous solution of table salt. This means that in salt water other than sodium chloride contain other salts. The average content (mass fraction, %) of salts in sea water is as follows: NaCl - 77,8, MgCl2 - 10,9, MgSO4 - 4,7 , K2SO4 - 2,5, 3, (O3)2 - 0,3, other salts - 0,2. The bitter taste of sea breeze is due precisely to magnesium salts.

Many know that table salt, which is in the moist air, dampens. Pure sodium chloride is a non-hygroscopic substance, that is, it does not attract moisture. Moieties of magnesium and calcium are hygroscopic. Their impurities are almost always contained in table salt and thanks to them, moisture absorption takes place.

In the earth's crust, rock salt beds are quite common. It is believed that they are obtained as a result of deformation of the earth's crust with layers of sedimentary rocks formed as a result of evaporation of sea water or salt lake water. Rock salt is squeezed upwards with deformations to form solid salt domes, usually having a rounded shape in plan and reaching several kilometers in diameter. One of such long-known deposits of rock salt is located near Iletsk in the Orenburg region. The salt dome of this deposit extends for 2 km in length, 1 km in width and extends further in 1 km.

Table salt is the most important raw material of the chemical industry. It produces soda, chlorine, hydrochloric acid, sodium hydroxide, sodium metal.

When studying the properties of soils, scientists have established that, being impregnated with sodium chloride, they do not pass water. If the bottom of the reservoir is covered with a layer of soil impregnated with NaCl, then no water leakage occurs.

Chemists are well aware that by mixing finely divided ice with table salt it is possible to obtain an effective cooling mixture. For example, a mixture of 30 g NaCl per 100 g ice is cooled to -200 C. This is because the aqueous solution of table salt freezes at low temperatures. Consequently, ice having a temperature of about 00 C, will melt in such a solution, taking away heat from the environment. This property of a mixture of ice and table salt can also be used successfully by housewives.

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