What is salt? Its characteristics and reserves are of interest to students planning to associate their future profession with physics and chemistry. It is this substance that is called the most abundant in nature. What is its composition? Salt consists of sodium and chlorine atoms. Chemically, this is a typical middle salt.
Prevalence in nature
This mineral in its composition may have some impurities. For example, iron compounds give the substance red shades. In nature, halite is found in the form of strong, fine-grained masses; in small quantities, table salt is in the form of cubic crystals.
Considering the main properties of table salt, we highlight the good solubility of this compound in water. That is why salt layers do not come to the surface, mining is carried out by the mine method. Halite is the main salt component of the seas and oceans, in addition, the high content of sodium chloride in underground mineral waters and salt lakes. Where else can you find such a composition? Salt is part of sedimentary rocks. For example, such strata are found in large numbers in Canada and America.
In addition to direct consumption in food, table salt is a raw material for the production of hydrochloric acid and other substances.
Education Options
Salt, whose electrical and thermal conductivity is high, is formed when salt water seeps through sand. After the evaporation of water, the precipitated salt accumulates in the sand, gradually forming huge saline strata.
The solubility of halite is almost independent of temperature; therefore, a solution is oversaturated, and huge salt deposits appear. Scientists were able to calculate that with the sudden evaporation of water in the seas and oceans from the remaining salt, it would be possible to build a wall 1 meter thick, 280 meters high, which could completely encircle our planet at the equator.
Types of deposits
Depending on what are the conditions for the occurrence of salt, distinguish its varieties:
- rock salt, which is between the layers in the solid state;
- self-settling rock, which is formed in the form of layers at the bottom of enclosed pools;
- volcanic salt;
- fading.
Mineral extraction and processing methods
Underground mining produces rock salt. When groundwater is evaporated, evaporated salt is obtained.
Among the exotic options for the extraction of this mineral, we note the deposition of salt from underground sources in Yakutia at low temperatures. The cheapest method of processing is the use of self-priming processes.
The thermal conductivity of table salt depends on its variety, humidity, and ambient temperature. This substance is an excellent raw material for the chemical industry. By electrolysis of its melt, chlorine gas and sodium metal are obtained. In the case of electrolysis of the solution, one of the reaction products is sodium hydroxide (alkali).
Sodium chloride is the main component not only of sea water, but also of blood serum. This substance is necessary for breathing and the full absorption of food. Without halite, which is not produced by the human body, there is no process of oxygen and nutrient transfer, impulse transmission, muscle functioning, including the heart muscle. An adult body contains about 250 grams of this substance, spent on a variety of physiological processes.
It is the salt that many scientists consider a natural antidepressant that improves mood. In the event of a lack of sodium chloride, a person develops depression, mental and nervous diseases, a problem with the digestive and cardiovascular systems, anorexia, muscle cramps. Excess salt threatens to increase blood pressure, kidney problems. Salt can be a deadly poison for the body!
Physical properties
What are its thermophysical properties? The thermal conductivity of sodium chloride decreases when water is absorbed. The salt is odorless, with a melting point of 801 ° C. On the Mohs scale, the hardness of halite is 2-2.5.
The thermal conductivity of salt explains its basic physical properties: density, boiling point. Sodium chloride has various shades associated with impurities that make up the natural mineral.
Since an ionic crystal lattice is formed between sodium cations and chlorine anions, the substance has a rather high boiling and melting point.
The thermal conductivity of sodium chloride is explained by the presence of an ionic crystal lattice in the molecules. The forces of attraction of particles in different directions propagate identically, ions are firmly connected with each other. When sodium chloride is heated to its melting temperature, the crystal structure is completely destroyed, and a liquid is formed from the solid state.
Of practical importance is not only the thermal conductivity of sodium chloride, but also the electrical conductivity of this substance.
Chemical properties
How does halite characterize chemistry? What are the physical properties of a salt substance? It is a solid and a conductor of current and heat. And with what simple and complex substances can it interact?
By reacting sodium chloride with concentrated sulfuric acid, hydrogen chloride is obtained, which is used in the chemical industry.
A qualitative reaction to chloride ions is the interaction with silver salts. The product of the interaction is a white precipitate of silver chloride.
Mixing solutions of sodium chloride and copper sulfate (2) leads to the formation of a complex compound, sodium tetrachlorocuprate, which has a green color.
Getting
How can i get sodium chloride? Salt, whose thermal conductivity of the solutions is high, is abundant in nature. That is why there is no point in developing industrial and laboratory methods for producing this compound. For example, you can get sodium chloride by synthesizing simple substances: chlorine and sodium.
Areas of use
In modern cooking and the food industry, sodium chloride is used, which has a purity of at least 97 percent. This substance acts as a flavoring agent, as well as in the form of a substance necessary for the preservation of food. It has a trade name - salt. Depending on what its origin is, they release sea, rock, fluorinated, iodized salt. In sodium chloride in a small amount there are compounds of calcium, potassium, magnesium, giving it rigidity and hygroscopicity.
Depending on the percentage of sodium chloride, several varieties are distinguished:
- "Extra" when the content is in an amount of more than 99.5%;
- first grade - 97.5%;
- the highest - 98.2%;
- the second is 97%.
Sodium chloride has insignificant antiseptic properties, therefore, a 10-15 percent solution of salt can avoid the multiplication of various putrefactive diseases. This property explains the use of sodium chloride as a preservative.
A 0.9% solution of sodium chloride is used in medicine in the form of a detoxification agent, which corrects the functioning of the human body systems during dehydration.
A 10% solution of this substance is used as an osmotic diuretic, indispensable in case of cerebral edema, as well as with bleeding. It is with this solution that purulent wounds are treated, and in ophthalmology it is used as a decongestant.
In winter, a mixture of sodium chloride, clay, sand (technical salt) is used as antifreeze. Sidewalks are sprinkled with this compound to combat icy. Of course, this mixture negatively affects the condition of shoes, road transport.
Sodium cation exchange filters are used to soften the water. For their regeneration, a 6-10% solution of sodium chloride is used.
Finally
Salt was used to preserve fish and meat products about a thousand years ago. Corned beef stocked up mainly for the ship kitchen. Herring was salted in Holland, and bacon was produced in England. In the X-XII centuries, the Slavs began to use salt to protect products from putrefactive microorganisms.
In addition to the food industry, sodium chloride is used in ferrous and non-ferrous metallurgy, in the processing of metals, in mechanical engineering, in the manufacture of furs, for the production of cooling solutions.
Most of the table salt produced goes to the chemical industry, where it goes to the production of caustic soda (sodium hydroxide) and chlorine. Among the industries the use of this mineral and the manufacture of fertilizers, as well as reagents for dyeing fabrics and soap production.
No one can say for sure when for the first time a person began to add salt to his daily food. At present, it is difficult to imagine those distant times when table salt was unknown to mankind.
As civilization developed, methods for the extraction of sodium chloride changed and improved, and the physical and chemical properties of this compound were studied. We hope that the article was interesting and useful for you!