DEFINITION

Calcium- the twentieth element of the periodic table. Designation - Ca from the Latin "calcium". Located in the fourth period, group IIA. Refers to metals. The core charge is 20.

Calcium is one of the most common elements in nature. The earth's crust contains approximately 3% (wt.). It occurs in numerous deposits of limestone and chalk, as well as marble, which are natural varieties of calcium carbonate CaCO 3 . Gypsum CaSO 4 × 2H 2 O, phosphorite Ca 3 (PO 4) 2 and, finally, various calcium-containing silicates are also found in large quantities.

In the form of a simple substance, calcium is a malleable, fairly hard, white metal (Fig. 1). In air it quickly becomes covered with a layer of oxide, and when heated it burns with a bright reddish flame. Calcium reacts relatively slowly with cold water, but quickly displaces hydrogen from hot water, forming hydroxide.

Rice. 1. Calcium. Appearance.

Atomic and molecular mass of calcium

The relative molecular mass of a substance (M r) is a number showing how many times the mass of a given molecule is greater than 1/12 the mass of a carbon atom, and the relative atomic mass of an element (A r) is how many times the average mass of atoms of a chemical element is greater than 1/12 mass of a carbon atom.

Since in the free state calcium exists in the form of monatomic Ca molecules, the values ​​of its atomic and molecular masses coincide. They are equal to 40.078.

Isotopes of calcium

It is known that in nature calcium can be found in the form of four stable isotopes 40 Ca, 42 Ca, 43 Ca, 44 Ca, 46 Ca and 48 Ca, with a clear predominance of the 40 Ca isotope (99.97%). Their mass numbers are 40, 42, 43, 44, 46 and 48, respectively. The nucleus of an atom of the calcium isotope 40 Ca contains twenty protons and twenty neutrons, and the remaining isotopes differ from it only in the number of neutrons.

There are artificial isotopes of calcium with mass numbers from 34 to 57, among which the most stable is 41 Ca with a half-life of 102 thousand years.

Calcium ions

At the outer energy level of the calcium atom there are two electrons, which are valence:

1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 .

As a result of chemical interaction, calcium gives up its valence electrons, i.e. is their donor, and turns into a positively charged ion:

Ca 0 -2e → Ca 2+ .

Calcium molecule and atom

In the free state, calcium exists in the form of monoatomic Ca molecules. Here are some properties characterizing the calcium atom and molecule:

Calcium alloys

Calcium serves as an alloying component in some lead alloys.

Examples of problem solving

EXAMPLE 1

Exercise

Write the reaction equations that can be used to carry out the following transformations: Ca → Ca(OH) 2 → CaCO 3 → Ca(HCO 3) 2.

Answer

By dissolving calcium in water, you can obtain a cloudy solution of a compound known as “milk of lime” - calcium hydroxide: Ca+ 2H 2 O→ Ca(OH) 2 + H 2. By passing carbon dioxide through a solution of calcium hydroxide we obtain calcium carbonate: 2Ca(OH) 2 + CO 2 → CaCO 3 + H 2 O. By adding water to calcium carbonate and continuing to pass carbon dioxide through this mixture, we obtain calcium bicarbonate: CaCO 3 + H 2 O + CO 2 → Ca(HCO 3) 2.

Calcium—an element of the main subgroup of the second group, the fourth period of the periodic system of chemical elements of D.I. Mendeleev, with atomic number 20. Denoted by the symbol Ca (Latin Calcium). The simple substance calcium (CAS number: 7440-70-2) is a soft, reactive alkaline earth metal of a silvery-white color.

History and origin of the name

The name of the element comes from Lat. calx (in the genitive case calcis) - “lime”, “soft stone”. It was proposed by the English chemist Humphry Davy, who isolated calcium metal by the electrolytic method in 1808. Davy electrolyzed a mixture of wet slaked lime and mercuric oxide HgO on a platinum plate, which served as the anode. The cathode was a platinum wire immersed in liquid mercury. As a result of electrolysis, calcium amalgam was obtained. Having distilled mercury from it, Davy obtained a metal called calcium. Calcium compounds - limestone, marble, gypsum (as well as lime - a product of calcination of limestone) have been used in construction for several thousand years ago. Until the end of the 18th century, chemists considered lime to be a simple solid. In 1789, A. Lavoisier suggested that lime, magnesia, barite, alumina and silica are complex substances.

Being in nature

Due to its high chemical activity, calcium does not occur in free form in nature.

Calcium accounts for 3.38% of the mass of the earth's crust (5th most abundant after oxygen, silicon, aluminum and iron).

Isotopes

Calcium occurs in nature as a mixture of six isotopes: 40 Ca, 42 Ca, 43 Ca, 44 Ca, 46 Ca and 48 Ca, of which the most common is 40 Ca and accounts for 96.97%.

Of the six natural isotopes of calcium, five are stable. The sixth isotope 48 Ca, the heaviest of the six and very rare (its isotopic abundance is only 0.187%), was recently discovered to undergo double beta decay with a half-life of 5.3 x 10 19 years.

In rocks and minerals

Most of the calcium is contained in silicates and aluminosilicates of various rocks (granites, gneisses, etc.), especially in feldspar - anorthite Ca.

In the form of sedimentary rocks, calcium compounds are represented by chalk and limestones, consisting mainly of the mineral calcite (CaCO 3). The crystalline form of calcite - marble - is much less common in nature.

Calcium minerals such as calcite CaCO 3 , anhydrite CaSO 4 , alabaster CaSO 4 ·0.5H 2 O and gypsum CaSO 4 ·2H 2 O, fluorite CaF 2 , apatites Ca 5 (PO 4) 3 (F,Cl, OH), dolomite MgCO 3 ·CaCO 3 . The presence of calcium and magnesium salts in natural water determines its hardness.

Calcium, vigorously migrating in the earth's crust and accumulating in various geochemical systems, forms 385 minerals (the fourth largest number of minerals).

Migration in the earth's crust

In the natural migration of calcium, a significant role is played by “carbonate equilibrium”, associated with the reversible reaction of the interaction of calcium carbonate with water and carbon dioxide with the formation of soluble bicarbonate:

CaCO 3 + H 2 O + CO 2 ↔ Ca (HCO 3) 2 ↔ Ca 2+ + 2HCO 3 -

(equilibrium shifts to the left or right depending on the concentration of carbon dioxide).

Biogenic migration plays a huge role.

In the biosphere

Calcium compounds are found in almost all animal and plant tissues (see also below). A significant amount of calcium is found in living organisms. Thus, hydroxyapatite Ca 5 (PO 4) 3 OH, or, in another entry, 3Ca 3 (PO 4) 2 ·Ca(OH) 2, is the basis of the bone tissue of vertebrates, including humans; The shells and shells of many invertebrates, eggshells, etc. are made of calcium carbonate CaCO 3. In living tissues of humans and animals there is 1.4-2% Ca (by mass fraction); In a human body weighing 70 kg, the calcium content is about 1.7 kg (mainly in the intercellular substance of bone tissue).

Receipt

Free metallic calcium is obtained by electrolysis of a melt consisting of CaCl 2 (75-80%) and KCl or CaCl 2 and CaF 2, as well as aluminothermic reduction of CaO at 1170-1200 °C:

4CaO + 2Al = CaAl 2 O 4 + 3Ca.

Properties

Physical properties

Calcium metal exists in two allotropic modifications. Up to 443 °C, α-Ca with a cubic face-centered lattice (parameter a = 0.558 nm) is stable; β-Ca with a cubic body-centered lattice of the α-Fe type (parameter a = 0.448 nm) is more stable. Standard enthalpy Δ H 0 transition α → β is 0.93 kJ/mol.

Chemical properties

In the series of standard potentials, calcium is located to the left of hydrogen. The standard electrode potential of the Ca 2+ /Ca 0 pair is −2.84 V, so that calcium actively reacts with water, but without ignition:

Ca + 2H 2 O = Ca(OH) 2 + H 2 + Q.

The presence of dissolved calcium bicarbonate in water largely determines the temporary hardness of water. It is called temporary because when water boils, bicarbonate decomposes and CaCO 3 precipitates. This phenomenon leads, for example, to the fact that scale forms in the kettle over time.

Application

Applications of calcium metal

The main use of calcium metal is as a reducing agent in the production of metals, especially nickel, copper and stainless steel. Calcium and its hydride are also used to produce difficult-to-reduce metals such as chromium, thorium and uranium. Calcium-lead alloys are used in batteries and bearing alloys. Calcium granules are also used to remove traces of air from vacuum devices.

Metallothermy

Pure metallic calcium is widely used in metallothermy for the production of rare metals.

Alloying of alloys

Pure calcium is used to alloy lead, which is used for the production of battery plates and maintenance-free starter lead-acid batteries with low self-discharge. Also, metallic calcium is used for the production of high-quality calcium babbits BKA.

Nuclear fusion

The isotope 48 Ca is the most effective and commonly used material for the production of superheavy elements and the discovery of new elements on the periodic table. For example, in the case of using 48 Ca ions to produce superheavy elements in accelerators, the nuclei of these elements are formed hundreds and thousands of times more efficiently than when using other “projectiles” (ions).) is used in the form and for the reduction of metals, as well as in the production of cyanamide calcium (by heating calcium carbide in nitrogen at 1200 °C, the reaction is exothermic, carried out in cyanamide furnaces).

Calcium, as well as its alloys with aluminum and magnesium, are used in backup thermal electric batteries as an anode (for example, calcium-chromate element). Calcium chromate is used in such batteries as a cathode. The peculiarity of such batteries is an extremely long shelf life (decades) in a suitable condition, the ability to operate in any conditions (space, high pressures), and a high specific energy in terms of weight and volume. Disadvantage: short lifespan. Such batteries are used where it is necessary to create colossal electrical power for a short period of time (ballistic missiles, some spacecraft, etc.).

In addition, calcium compounds are included in medications for the prevention of osteoporosis, and in vitamin complexes for pregnant women and the elderly.-

Biological role of calcium

Calcium is a common macronutrient in the body of plants, animals and humans. In humans and other vertebrates, most of it is contained in the skeleton and teeth in the form of phosphates. The skeletons of most groups of invertebrates (sponges, coral polyps, mollusks, etc.) consist of various forms of calcium carbonate (lime). Calcium ions are involved in blood clotting processes, as well as in ensuring constant osmotic pressure of the blood. Calcium ions also serve as one of the universal second messengers and regulate a variety of intracellular processes - muscle contraction, exocytosis, including the secretion of hormones and neurotransmitters, etc. The calcium concentration in the cytoplasm of human cells is about 10−7 mol, in intercellular fluids about 10− 3 mol.

Calcium requirements depend on age. For adults, the required daily intake is from 800 to 1000 milligrams (mg), and for children from 600 to 900 mg, which is very important for children due to the intensive growth of the skeleton. Most of the calcium that enters the human body with food is found in dairy products; the remaining calcium comes from meat, fish, and some plant products (especially legumes). Absorption occurs in both the large and small intestines and is facilitated by an acidic environment, vitamin D and vitamin C, lactose, and unsaturated fatty acids. The role of magnesium in calcium metabolism is important; with its deficiency, calcium is “washed out” from the bones and deposited in the kidneys (kidney stones) and muscles.

Aspirin, oxalic acid, and estrogen derivatives interfere with the absorption of calcium. When combined with oxalic acid, calcium produces water-insoluble compounds that are components of kidney stones.

Due to the large number of processes associated with it, the calcium content in the blood is precisely regulated, and with proper nutrition, a deficiency does not occur. Prolonged absence from the diet can cause cramps, joint pain, drowsiness, growth defects, and constipation. Deeper deficiency leads to constant muscle cramps and osteoporosis. Abuse of coffee and alcohol can cause calcium deficiency, since some of it is excreted in the urine.

Excessive doses of calcium and vitamin D can cause hypercalcemia, followed by intense calcification of bones and tissues (mainly affecting the urinary system). Long-term excess disrupts the functioning of muscle and nerve tissues, increases blood clotting and reduces the absorption of zinc by bone cells. The maximum daily safe dose for an adult is 1500 to 1800 milligrams.

Pregnant and breastfeeding women - from 1500 to 2000 mg.

Calcium has been known to man since ancient times in the form of alkaline compounds such as chalk or limestone. This element was obtained in its pure form at the beginning of the 19th century. It was then established that, in terms of its basic properties, calcium belongs to the alkali metals.

Calcium plays an important biological role - it is the main constituent macroelement of the skeleton (including the external one) in most species on the planet, is part of hormones, and is a regulator of neural and muscle interactions. Chemically pure calcium is used in various reactions, in metallurgy and in many other industries.

general characteristics

Calcium is one of the typical representatives of the family of active alkali metals. In its pure form, the texture and appearance resembles iron, with a less pronounced shine. Brittle, breaks with the formation of heterogeneous crystalline granules. Calcium is best known in the form of its compounds (chalk, limestone, silica and others), where it has the appearance of a whitish crumbling substance.

It is not found in its pure form due to its high reactivity. It is part of most minerals, among which the most important are marble, granite, alabaster and some other valuable rocks.

Basic physical and chemical properties

Belongs to the second group of the periodic table of elements, exhibiting similar physical properties to other representatives of the alkaline group:

• Relatively low density (1.6 g/cm3);
• The melting temperature limit is 840 0 C under normal conditions;
• The average thermal conductivity is generally noticeably lower than that of most metals;

Overall, the physics of calcium doesn't present much of a surprise. Possessing a typical crystal lattice, this element has rather low strength and almost zero ductility, easily crumbles and breaks with the formation of a characteristic crystalline pattern at the fracture boundary.

However, recent studies have shown very interesting results. It has been established that at high atmospheric pressure, the physical properties of the element begin to change. Semiconductor properties appear that are absolutely uncharacteristic of any metals. Extreme pressure leads to the appearance of superconducting properties of calcium. These studies have far-reaching implications, but so far the applications of calcium are limited to its conventional properties.

In its chemical properties, calcium does not stand out in any way and is a typical alkaline earth metal:

• High reactivity;
• Willing interaction with the atmosphere and the formation of a characteristic dull film on the surface of the element;
• Actively interacts with water, but, unlike elements such as sodium, an explosive exothermic reaction does not occur;
• Reacts with all active non-metals, including iodine and bromine;

Unlike the more active alkali metals, calcium requires a catalyst or strong heat to react with metals and relatively inert elements (for example, carbon). Calcium is stored in tightly sealed glass containers to prevent spontaneous reactions.

Calcium is one of the five most common substances on the planet, second only to oxygen, silicon and aluminum with iron. Moreover, in nature this element is found mainly in the form of solid or granular minerals. The best known calcium compound is limestone. Calcium also forms a wide range of different minerals, from the above-mentioned granite and marble, to the less common barites and spars. According to approximate estimates of researchers, the calcium content in pure equivalent is about 3.4% by weight.

Industrial Applications

In the industrial sphere, calcium is one of the group of widely demanded materials for metallurgy purposes. With its help, purified metals are obtained, including uranium and thorium, as well as some rare earth elements. Adding calcium to steel melts helps bind and remove free oxygen, which improves the structural properties of the metal alloy. Calcium is also used as an electrolytic element in batteries and batteries.

Natural calcium compounds (chalk, marble, limestone, gypsum) and the products of their simplest processing (lime) have been known to people since ancient times. In 1808, the English chemist Humphry Davy electrolyzed wet slaked lime (calcium hydroxide) with a mercury cathode and obtained calcium amalgam (an alloy of calcium and mercury). From this alloy, having distilled off mercury, Davy obtained pure calcium.
He also proposed the name of a new chemical element, from the Latin "calx" denoting the name of limestone, chalk and other soft stones.

Finding in nature and obtaining:

Calcium is the fifth most abundant element in the earth's crust (more than 3%), forms many rocks, many of which are based on calcium carbonate. Some of these rocks are of organic origin (shell rock), showing the important role of calcium in living nature. Natural calcium is a mixture of 6 isotopes with mass numbers from 40 to 48, with 40 Ca accounting for 97% of the total. Nuclear reactions have also produced other isotopes of calcium, for example radioactive 45 Ca.
To obtain a simple calcium substance, electrolysis of molten calcium salts or aluminothermy is used:
4CaO + 2Al = Ca(AlO 2) 2 + 3Ca

Physical properties:

A silver-gray metal with a cubic face-centered lattice, much harder than the alkali metals. Melting point 842°C, boiling point 1484°C, density 1.55 g/cm3. At high pressures and temperatures of about 20 K it goes into the superconductor state.

Chemical properties:

Calcium is not as active as alkali metals, but it must be stored under a layer of mineral oil or in tightly sealed metal drums. Already at normal temperatures it reacts with oxygen and nitrogen in the air, as well as with water vapor. When heated, it burns in air with a red-orange flame, forming an oxide with an admixture of nitrides. Like magnesium, calcium continues to burn in an atmosphere of carbon dioxide. When heated, it reacts with other non-metals, forming compounds that are not always obvious in composition, for example:
Ca + 6B = CaB 6 or Ca + P => Ca 3 P 2 (also CaP or CaP 5)
In all its compounds, calcium has an oxidation state of +2.

The most important connections:

Calcium oxide CaO- ("quicklime") a white substance, an alkaline oxide, which reacts vigorously with water ("quenched") turning into a hydroxide. Obtained by thermal decomposition of calcium carbonate.

Calcium hydroxide Ca(OH) 2- ("slaked lime") white powder, slightly soluble in water (0.16g/100g), strong alkali. A solution (“lime water”) is used to detect carbon dioxide.

Calcium carbonate CaCO 3- the basis of most natural calcium minerals (chalk, marble, limestone, shell rock, calcite, Iceland spar). In its pure form, the substance is white or colorless. crystals. When heated (900-1000 C) decomposes, forming calcium oxide. Not p-rim, reacts with acids, is able to dissolve in water saturated with carbon dioxide, turning into bicarbonate: CaCO 3 + CO 2 + H 2 O = Ca(HCO 3) 2. The reverse process leads to the appearance of calcium carbonate deposits, in particular formations such as stalactites and stalagmites
It is also found in nature as part of dolomite CaCO 3 * MgCO 3

Calcium sulfate CaSO 4- a white substance, in nature CaSO 4 * 2H 2 O (“gypsum”, “selenite”). The latter, when carefully heated (180 C), turns into CaSO 4 *0.5H 2 O (“burnt gypsum”, “alabaster”) - a white powder, which, when mixed with water, again forms CaSO 4 *2H 2 O in the form of a solid, quite durable material. Slightly soluble in water, it can dissolve in excess sulfuric acid, forming hydrogen sulfate.

Calcium phosphate Ca 3 (PO 4) 2- (“phosphorite”), insoluble, under the influence of strong acids it turns into more soluble calcium hydro- and dihydrogen phosphates. Feedstock for the production of phosphorus, phosphoric acid, phosphate fertilizers. Calcium phosphates are also included in apatites, natural compounds with the approximate formula Ca 5 3 Y, where Y = F, Cl, or OH, respectively, fluorine, chlorine, or hydroxyapatite. Along with phosphorite, apatites are part of the bone skeleton of many living organisms, incl. and man.

Calcium fluoride CaF 2 - (natural:"fluorite", "fluorspar"), an insoluble substance of white color. Natural minerals have a variety of colors due to impurities. Glows in the dark when heated and under UV irradiation. It increases the fluidity (“fusibility”) of slags when producing metals, which explains its use as a flux.

Calcium chloride CaCl 2- colorless christ. It is well soluble in water. Forms crystalline hydrate CaCl 2 *6H 2 O. Anhydrous ("fused") calcium chloride is a good desiccant.

Calcium nitrate Ca(NO 3) 2- ("calcium nitrate") colorless. christ. It is well soluble in water. An integral part of pyrotechnic compositions that gives the flame a red-orange color.

Calcium carbide CaС 2- reacts with water, forming acetylene, for example: CaС 2 + H 2 O = С 2 H 2 + Ca(OH) 2

Application:

Metallic calcium is used as a strong reducing agent in the production of some difficult-to-reduce metals (“calciothermy”): chromium, rare earth elements, thorium, uranium, etc. In the metallurgy of copper, nickel, special steels and bronzes, calcium and its alloys are used to remove harmful impurities of sulfur, phosphorus, excess carbon.
Calcium is also used to bind small amounts of oxygen and nitrogen when obtaining high vacuum and purifying inert gases.
Neutron-excess 48 Ca ions are used for the synthesis of new chemical elements, for example element No. 114, . Another isotope of calcium, 45Ca, is used as a radioactive tracer in studies of the biological role of calcium and its migration in the environment.

The main area of ​​application for numerous calcium compounds is the production of building materials (cement, building mixtures, plasterboard, etc.).

Calcium is one of the macroelements in living organisms, forming compounds necessary for the construction of both the internal skeleton of vertebrates and the external skeleton of many invertebrates, the shell of eggs. Calcium ions also participate in the regulation of intracellular processes and determine blood clotting. Lack of calcium in childhood leads to rickets, in old age - to osteoporosis. The source of calcium is dairy products, buckwheat, nuts, and its absorption is facilitated by vitamin D. If there is a lack of calcium, various drugs are used: calcex, calcium chloride solution, calcium gluconate, etc.
The mass fraction of calcium in the human body is 1.4-1.7%, the daily requirement is 1-1.3 g (depending on age). Excessive calcium intake can lead to hypercalcemia - deposition of its compounds in internal organs, and the formation of blood clots in blood vessels. Sources:
Calcium (element) // Wikipedia. URL: http://ru.wikipedia.org/wiki/Calcium (access date: 01/3/2014).
Popular library of chemical elements: Calcium. // URL: http://n-t.ru/ri/ps/pb020.htm (01/3/2014).

History of calcium

Calcium was discovered in 1808 by Humphry Davy, who, by electrolysis of slaked lime and mercuric oxide, obtained calcium amalgam, as a result of the process of distilling mercury from which the metal remained, called calcium. In Latin lime sounds like calx, it was this name that was chosen by the English chemist for the discovered substance.

Calcium is an element of the main subgroup II of group IV of the periodic table of chemical elements D.I. Mendeleev, has an atomic number of 20 and an atomic mass of 40.08. The accepted designation is Ca (from the Latin - Calcium).

Physical and chemical properties

Calcium is a reactive soft alkali metal with a silvery-white color. Due to interaction with oxygen and carbon dioxide, the surface of the metal becomes dull, so calcium requires a special storage regime - a tightly closed container, in which the metal is filled with a layer of liquid paraffin or kerosene.

Calcium is the most well-known of the microelements necessary for humans; the daily requirement for it ranges from 700 to 1500 mg for a healthy adult, but it increases during pregnancy and lactation; this must be taken into account and calcium must be obtained in the form of preparations.

Being in nature

Calcium has very high chemical activity, therefore it is not found in nature in its free (pure) form. However, it is the fifth most common in the earth's crust; it is found in the form of compounds in sedimentary (limestone, chalk) and rocks (granite); feldspar anorite contains a lot of calcium.

It is quite widespread in living organisms; its presence has been found in plants, animals and humans, where it is present mainly in teeth and bone tissue.

Calcium absorption

An obstacle to the normal absorption of calcium from food is the consumption of carbohydrates in the form of sweets and alkalis, which neutralize the hydrochloric acid of the stomach, which is necessary to dissolve calcium. The process of calcium absorption is quite complex, so sometimes it is not enough to get it only from food; additional intake of the microelement is necessary.

Interaction with others

To improve the absorption of calcium in the intestine, it is necessary, which tends to facilitate the process of calcium absorption. When taking calcium (in the form of supplements) while eating, absorption is blocked, but taking calcium supplements separately from food does not affect this process in any way.

Almost all of the body's calcium (1 to 1.5 kg) is found in bones and teeth. Calcium is involved in the processes of excitability of nervous tissue, muscle contractility, blood clotting processes, is part of the nucleus and membranes of cells, cellular and tissue fluids, has anti-allergic and anti-inflammatory effects, prevents acidosis, and activates a number of enzymes and hormones. Calcium is also involved in the regulation of cell membrane permeability and has the opposite effect.

Signs of calcium deficiency

Signs of calcium deficiency in the body are the following, at first glance, unrelated symptoms:

• nervousness, worsening mood;
• cardiopalmus;
• convulsions, numbness of extremities;
• slowing of growth and children;
• high blood pressure;
• splitting and brittleness of nails;
• joint pain, lowering the “pain threshold”;
• heavy menstruation.

Causes of calcium deficiency

Causes of calcium deficiency may include unbalanced diets (especially fasting), low calcium content in food, smoking and addiction to coffee and caffeine-containing drinks, dysbacteriosis, kidney disease, thyroid disease, pregnancy, lactation and menopause.

Excess calcium, which can occur with excessive consumption of dairy products or uncontrolled use of drugs, is characterized by extreme thirst, nausea, vomiting, loss of appetite, weakness and increased urination.

Uses of calcium in life

Calcium has found application in the metallothermic production of uranium, in the form of natural compounds it is used as a raw material for the production of gypsum and cement, as a means of disinfection (well-known bleach).