Salt is widely used in food industry, medicine, animal husbandry, cosmetology, etc. since ancient times. This white crystalline powder is obtained by various methods. This may be, for example, evaporation of sea water, mining in quarries, collecting from the bottom of lakes. But in any case, the final product always has the same physical characteristics. For example, what is the salt hardness on the Mohs scale? We will talk about later in the article. We also figure out what other characteristics this very popular product has.
What is the Mohs scale
One of the hallmarks of many substances on the planet is the degree of hardness. It is customary to determine this parameter according to a special scheme called the Mohs scale. To facilitate the task of comparing the hardness of different substances, 10 reference elements are included in this system. The hardness of these substances is checked simply by scratching.
In first place in the Mohs scale is the hardest mineral on the planet - diamond. This gem is not known to be scratched even by a strong steel knife. The Mohs diamond hardness is therefore 10. In the second place in this pattern are corundums - rubies and sapphires. Their hardness is 9. The softest reference substances of the Mohs scale are talc and chalk. Their hardness in this scheme is defined as 1.
What is salt?
The chemical formula of this substance is as follows: NaCl. In another way, sodium chloride is also called sodium chloride or rock salt. When ground, this food product is a colorless crystal. The latter may have different sizes. In any case, the mass of the salt is white.
The main feature of sodium chloride, as you know, is the characteristic taste. In everyday life and in the food industry, table salt can be added to a wide variety of products. As scientists have found, sodium chloride is a substance without which human life is impossible at all.
What is the Mohs salt hardness
In nature, sodium chloride is a very common substance. Therefore, rock salt was, among other things, included as a reference in the Mohs scale. Sodium chloride is in the penultimate ninth place in this scheme. That is, the hardness of salt is two. Sodium chloride crystals are known to be brittle and readily soluble in water. Salt grains look quite hard. However, the impression is largely misleading. In fact, salt crystals are easily scratched even with just a fingernail.
Linear hardness
Thus, as we found out, NaCl is the last but one place on the Mohs scale of hardness. The linear hardness of minerals according to this scheme is also very easy to determine. Of course, for reference sodium chloride, this characteristic is known.
The relative indicator for salt, as we found out, is 2. What is the salt hardness absolute on the Mohs hardness scale? For NaCl, this indicator is 3.
Minerals with a similar hardness
Salt, therefore, is a fairly soft substance. There are many similar minerals in nature. For example, gypsum, mica, and chlorite have the same absolute and relative hardness indices as NaCl; All these substances are easily scratched with a fingernail.
Of course, there is a place on the relative Mohs hardness scale for sugar. Salt on the scale is used as one of the reference substances. Sugar, although it is also a very common food product, was not initially noted on the Mohs scheme. However, the hardness of this substance, like any other, is of course also known. Sugar is slightly softer than salt, but on the Mohs scale, its hardness is also 2.
Other physical characteristics
So, what is the hardness of salt on the Mohs scale, we found out. But what other properties does this substance have?
In mineralogy, ordinary table salt or rock salt is called halite. The history of this transparent stone goes back millions of years. Halite forms in the form of cubic crystals, the color of which can vary from colorless to pinkish or yellow. The color of this mineral can be associated with the type of impurities present in its thickness.
Halite can be found in the wild most often in layers of chemogenic sedimentary rocks, as well as in bottom sediments of drying lakes and estuaries.
The main physical properties of the salt are:
- ability to dissolve in water;
- ability to crystallize on objects;
- salty taste;
- density - 2.165 g / cm 3 at a temperature of 20 ° C;
- melting point - 801 ° C;
- boiling point - 1413 ° C;
- solubility in water - 359 g / l at 20 ° C.
The taste of NaCl is pronounced. But no one can ever smell the salt. The Mohs hardness of this substance is small, and it is also brittle. Small particles of salt, for example, in places of its occurrence, can fly in the air and even get into a person’s nose. However, the person responsible for the perception of this substance is not available. Some people claim that they can smell salt. However, in this case it is still not NaCl, but various impurities contained in this substance.
Solubility
Among the features of salt, among other things, can be attributed to the fact that its solubility in water does not depend much on the temperature of the latter. This indicator in NaCl increases by 7 g from 0 to 100 ° C. However, the solubility of the salt is significantly reduced if MgCl 2 or CaCl 2 is contained in the water. This indicator sharply increases in NaCl with increasing pressure. There is a process of dissolution of salt with significant absorption of heat. This substance practically does not dissolve in alcohol.
Chemical properties
In its composition, NaCl belongs to the group of medium salts. The chemical composition of salt is as follows:
In its pure form, the composition of this substance is fully consistent with the theoretical. In the form of an isomorphic impurity, sodium chloride contains Br (up to 0.098%). Also, halite may include: NH3, He, As, J, Pb and some other substances. Atoms in the structure of Na and Cl alternate uniformly at the nodes of the crystalline cubic lattice.
Sizes of salt crystals can reach significant. Also, skeletal formations are characteristic of halite - fragile, muddy-white boat pyramids.
Other properties of salt
The salt hardness on the Mohs hardness scale is thus 2. The substance is brittle enough and dissolves well in water. Also a feature of NaCl is that it does not conduct electricity. In addition, this substance belongs to the group of demagnets. The salt fluoresces in red if it contains Mn.
Methods of Artificial Production
Get rock salt for the food industry or, for example, medicine can using different technologies. In laboratories for the extraction of NaCl usually use brines of underground dissolution of rock salt. This allows you to get the most pure product without impurities in industrial production. Underground brines in this case are subjected to normal evaporation. In this case, pure salt with hardness on the Mohs scale of hardness 2 is obtained. Evaporation of brines using this technique is carried out in special multi-unit plants.
Interesting Facts
The salt hardness on the Mohs hardness scale is precisely determined. This indicator for NaCl is 2. People thought about the physical and chemical properties of salt not so long ago. But man himself used this substance for various purposes from ancient times. First of all, salt has always been used, of course, primarily as a food product. However, sometimes she could perform other functions in society. For example, in Ethiopia, this substance was used as a currency until the 20th century.
In the Middle Ages, salt was so expensive that it was sometimes called white gold. In Germany, for example, there is still a special “salt pavement” along which this valuable food product was once transported between cities located on the Baltic Sea.
For the human body, salt is indeed a very important product. If you drink a very large amount of water, this substance will be washed out of the tissues. In this case, a person may even experience fatal hyponatremia.
The lack of salt in the human body is thus very dangerous. But an overabundance of this substance, of course, cannot be useful. Eating too much salt at a time is by no means impossible. The adoption of this substance in an amount of 1 g per 1 kg of weight can lead to death.