How to get calcium. Physical properties calcium

16.10.2019

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Ufa State Petroleum Technical University

Department of "General and Analytical Chemistry"

on the topic: "Calcium element. Properties, receipt, application "

Prepared a student of the BTS-11-01 group of surveillance G.L.

Associate Professor Krasko S.A.

Introduction

History and origin of the name

Finding in nature

Obtaining

Physical properties

Chemical properties

Application of metallic calcium

Use calcium compounds

Biological role

Conclusion

Bibliography

Introduction

Calcium is an element of the main subgroup of the second group, the fourth period of the periodic system of chemical elements D. I. Mendeleev, with atomic number 20. is indicated by the symbol of Ca (lat. Calcium). Simple calcium substance (CAS number: 7440-70-2) - soft, chemically active silver-white metal-white metal.

Calcium is called alkaline earth metal, it is believed to s - elements. At the external electron level in calcium, two electrons, so it gives compounds: Cao, Ca (OH) 2, CaCl2, Caso4, Caco3, etc. Calcium refers to typical metals - it has a large affinity for oxygen, restores almost all metals from their oxides, forms a rather strong base of Ca (OH) 2.

Despite the widespread prevalence of the element number 20, even chemists and then not everyone saw elementary calcium. But this metal and externally and on behavior is not at all similar to alkali metals, communicating with which is fraught with the danger of fires and burns. It can be calmly stored in the air, it does not ignite from the water.

The elementary calcium is almost not applied as a structural material. For this, it is too active. Calcium easily reacts with oxygen, gray, halogens. Even with nitrogen and hydrogen under certain conditions, it enters the reaction. Carbon oxide medium, inert for most metals, for calcium - aggressive. It burns in the atmosphere CO and CO2.

History and origin of the name

The name of the element comes from the lat. CALX (in the Parental Calcis Padder) - "Lime", "Soft Stone". It was proposed by the English chemist Humphrey Davy, in 1808 we allocated metal calcium with electrolytic method. Davy subjected the electrolysis mixture of a wet gasheny lime with HGO mercury oxide on a platinum plate, which was an anode. The cathode served as a platinum wire, immersed in liquid mercury. As a result of electrolysis, calcium amalgam was obtained. Heat from her mercury, Davy got a metal called Calcium.

Calcium compounds - limestone, marble, plaster (as well as lime - limestone firing product) were used in the construction case for several thousand years ago. Until the end of the XVIII century, chemists considered lime with a simple body. In 1789, A. Lavauzier suggested that lime, magnesia, barite, alumina and silica - compound substances.

Finding in nature

Due to the high chemical activity of calcium in free form in nature, it is not found.

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

Isotopes. Calcium is found in nature in the form of a mixture of six isotopes: 40CA, 42CA, 43CA, 44CA, 46CA and 48CA, among which the most common - 40CA is 96.97%.

Of the six natural isotopes of calcium, five are stable. The sixth isotope 48ca, the heaviest of six and very rare (its isotopic prevalence is only 0.187%), as it was recently discovered, experiencing a double beta decay with a half-life of 5.3 × 1019. years.

In rocks and minerals. Most of the calcium is contained as part of silicates and aluminosilicates of various rocks (granites, gneisses, etc.), especially in the field Plug - Animal CA.

In the form of sedimentary solids, calcium is represented by chalk and limestones consisting mainly of calcite mineral (Caco3). Crystalline form of calcite - marble - occurs in nature much less often.

Calcite CaCO3, Caso4 Anhydrite, Caso4 Alabaster · 0.5H2O and Caso4 Gyps 2H2O, Fluorite CAF2, CA5 Apatites (PO4) 3 (F, CL, OH), Dolomite MGCO3 · Ca5 (PO4) 3 (F, CL, OH), Dolomite MGCO3 · Caco3 is quite widespread. The presence of calcium and magnesium salts in natural water is determined by its rigidity.

Calcium, energetically migrating in the earth's crust and accumulating in various geochemical systems, forms 385 minerals (fourth place in terms of minerals).

Migration in the earth's crust. In the natural migration of calcium, a "carbonate equilibrium" plays a significant role associated with a reversible reaction of the interaction of calcium carbonate with water and carbon dioxide to form a soluble hydrocarbonate:

SASO3 + H2O + CO2 ↔ SA (NSO3) 2 ↔ CA2 + 2HCO3ˉ

(Equilibrium is shifted to the left or right depending on the concentration of carbon dioxide).

Biogenic migration. In the calcium compound biosphere, there are practically in all animals and vegetable tissues (see. Below). A significant amount of calcium is included in living organisms. Thus, hydroxyapatite CA5 (PO4) 3OH, or, in another record, 3CA3 (PO4) 2 · CA (OH) 2 - the base of the bone vertebral bone tissue, including a person; Caco3 calcium carbonate consists of sinks and polyziri of many invertebrates, egg shell, etc. in the living tissues of man and animals 1.4-2% Ca (by mass fraction); In the human body weighing 70 kg calcium content - about 1.7 kg (mainly in the composition of the intercellular substance of bone tissue).

Obtaining

Free metallic calcium is obtained by the electrolysis of the melt consisting of CaCl2 (75-80%) and KCl or from CaCl2 and CAF2, as well as aluminothermic recovery of Cao at 1170-1200 ° C:

Cao + 2Al \u003d Caal2O4 + 3CA.

A method of obtaining calcium is also developed by the thermal dissociation of calcium carbide CAC2

Physical properties

Calcium metal exists in two allotropic modifications. Up to 443 ° C stable α -Ca with cubic grille, above stable β-CA. with cubic volume-centered type grid α -Fe. Standard enthalpy ΔH0. transition α → β this is 0.93 kJ / mol.

Calcium - light metal (d \u003d 1.55), silver-white color. It is more hard and melted at a higher temperature (851 ° C) compared to sodium, which is located next to it in the periodic system. This is explained by the fact that one ion calcium in the metal accounts for two electrons. Therefore, the chemical bond between ions and electron gas is more durable than sodium. With chemical reactions, calcium valence electrons go to atoms of other elements. At the same time, two-charged ions are formed.

Chemical properties

Calcium - typical alkaline earth metal. The chemical activity of calcium is high, but lower than all other alkaline earth metals. It easily interacts with oxygen, carbon dioxide and air moisture, due to which the surface of the metal calcium is usually dimly grazing, therefore, in the calcium laboratory, it is usually stored, like other alkaline earth metals, in a tightly closed can under a layer of kerosene or liquid paraffin.

In the number of standard calcium potentials is located to the left of hydrogen. The standard electrode potential of the CA2 + / CA0 -2.84 B pair, so calcium actively reacts with water, but without ignition:

2N2O \u003d Ca (OH) 2 + H2 + Q.

With active non-metals (oxygen, chlorine, bromine), calcium reacts under normal conditions:

Ca + O2 \u003d 2SAO, CA + BR2 \u003d CABR2.

When heated in air or in calcium oxygen is flammable. With less active non-metals (hydrogen, boron, carbon, silicon, nitrogen, phosphorus, and other), calcium enters into interaction when heated, for example:

Sa + H2 \u003d San2, CA + 6B \u003d CAB6,

Ca + N2 \u003d Ca3N2, CA + 2C \u003d CAC2,

CA + 2P \u003d CA3R2 (calcium phosphide),

also known phosphides of calcium compositions of SAR and SAR5;

Ca + Si \u003d CA2SI (calcium silicide),

calcium calcium silicides are also known. CASI, CA3SI4 and CASI2 compounds.

The flow of the above reactions is usually accompanied by the release of a large amount of heat (that is, these reactions are exothermic). In all connections with non-metals, the degree of calcium oxidation is +2. Most of the calcium compounds with non-metals are easily decomposed with water, for example:

CAH2 + 2N2O \u003d CA (OH) 2 + 2N2, N2 + 3N2O \u003d 3A (OH) 2 + 2NH3.

Ion Ca2 + Besmevetn. When in the flame of soluble calcium salts, the flame is painted in brick-red.

Calcium salts such as CaCl2 chloride, CABR2 bromide, CAI2 iodide and Ca nitrate (NO3) 2 are well soluble in water. Insoluble in water Fluoride CAF2, Caco3 carbonate, Caso4 sulfate, orthophosphate CA3 (PO4) 2, SAS2O4 oxalate and some others.

The factory is important that, in contrast to calcium carbonate CASSO3, acid calcium carbonate (hydrocarbonate) Ca (NSO3) 2 in water is soluble. In nature, this leads to the following processes. When cool rain or river water, saturated with carbon dioxide, penetrates under the ground and falls on limestone, then their dissolution is observed:

Saso3 + CO2 + H2O \u003d CA (NSO3) 2.

In the same places where the water saturated with calcium bicarbonate goes to the surface of the Earth and heated by the solar rays, the reverse reaction flows:

Ca (NSO3) 2 \u003d Saso3 + CO2 + H2O.

So in nature the transfer of large masses. As a result, huge failures may form underground, and beautiful stone "icicles" - stalactites and stalagmites are formed in the caves.

The presence of a dissolved calcium bicarbonate in water largely determines the time rigidity of water. It is called temporary because, when boiling water, the bicarbonate is decomposed, and Saso3 falls into the precipitate. This phenomenon leads, for example, to the fact that in the teapot, scale is formed.

calcium metallic chemical physical

The main use of metal calcium is the use of it as a reducing agent when producing metals, especially nickel, copper and stainless steel. Calcium and its hydride are also used to obtain hard-established metals, such as chrome, thorium and uranium. Calcium alloys with lead are used in batteries and bearing alloys. Calcium granules are also used to remove traces of air from electrovacuum instruments. Saluble calcium and magnesium salts cause the overall rigidity of water. If they are present in water in small quantities, the water is called soft. With the large content of these salts, water is considered a rigid. Stiffness is eliminated when boiling, it is sometimes distilled water to completely eliminate.

Metalothermia

Pure metallic calcium is widely used in metalothermia when obtaining rare metals.

Alloy doping

Pure calcium is used to doping lead, which is on the manufacture of battery plates, maintainable starter lead-acid batteries with a small self-discharge. Also, the metal calcium is on the production of high-quality calcium babbits of the BKA.

Nuclear fusion

Isotope 48CA is the most efficient and consumer material for the production of super-temperature elements and the discovery of new elements of the Mendeleev table. For example, in the case of using 48CA ions to obtain superheuma elements on the core accelerators of these elements, hundreds and thousands of times more efficiently than when using other shells (ions).

Use calcium compounds

Hydride calcium. Calcium heating in the hydrogen atmosphere is obtained by Cah2 (calcium hydride) used in metallurgy (metal) and when producing hydrogen in the field.

Optical and laser materials. Calcium fluoride (fluorite) is used in the form of single crystals in optics (astronomical lenses, lenses, prisms) and as laser material. Calcium Tungsten (Sheelit) in the form of single crystals is used in laser technology, as well as as a scintillator.

Calcium carbide. Calcium carbide CAC2 is widely used to obtain acetylene and for the restoration of metals, as well as when producing calcium cyanamide (heating the calcium carbide in nitrogen at 1200 ° C, the reaction comes exothermally, is carried out in cyanamide furnaces).

Chemical current sources. Calcium, as well as its alloys with aluminum and magnesium, are used in the backup thermal electrical batteries as an anode (for example, calcium-chromium element). Calcium chromate is used in such batteries as a cathode. The peculiarity of such batteries is an extremely long period of storage (decade) at suitable condition, the possibility of operation in any conditions (space, high pressure), large specific energy in weight and volume. Disadvantage in short time. Such batteries are used where it is necessary to create a colossal electrical power for a short time (ballistic missiles, some spacecraft I.D.).

Refractory materials. Calcium oxide, both in free form and in the composition of ceramic mixtures, is used in the production of refractory materials.

Medicines. In medicine, Ca drugs eliminates violations associated with the lack of SA ions in the body (during tenania, spasmophilia, rickets). CA preparations reduce increased sensitivity to allergens and are used to treat allergic diseases (serum disease, sleepy fever, etc.). CA preparations reduce the increased permeability of the vessels and have an anti-inflammatory effect. They are used in hemorrhagic vasculite, radiation disease, inflammatory processes (pneumans, pleurisy, etc.) and certain skin diseases. Prescribed as a hemostatic agent, to improve the activities of the heart muscle and enhancing the effects of drugs, as an antidote in the poisoning of magnesium salts. Together with other means, Ca preparations are used to stimulate generic activities. Chloride Ca is introduced through the mouth and intravenously.

Ca preparations also include gypsum (sso4), used in surgery for gypsum bandages, and chalk (SASO3), prescribed inside with increased acidity of gastric juice and for the preparation of dental powder.

Biological role

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

Most of the calcium entering the human body with food is found in dairy products, the remaining calcium comes from meat, fish, and some vegetable products (especially much contain bean). Suction occurs both in a thick and small intestines and is facilitated by an acidic medium, vitamin D and vitamin C, lactose, unsaturated fatty acids. It is important for the role of magnesium in calcium exchange, with its lack of calcium "washed out" from the bones and deposits in the kidneys (kidney stones) and muscles.

Calcium absorption is hampered aspirin, oxalic acid, derivatives of estrogen. Connecting with oxalic acid, calcium gives insoluble compounds in water, which are components of stones in the kidneys.

Calcium content in the blood due to the large number of processes related to it is precisely adjustable, and with proper nutrition, the deficit does not occur. A long absence in the diet may cause cramps, pain in the joints, drowsiness, growth defects, as well as constipation. A deeper deficit leads to constant muscle cramps and osteoporosis. Abuse of coffee and alcohol may be causes of calcium deficiency, as part of it is removed with the urine.

Excessive doses of calcium and vitamin D can cause hypercalcemia, after which intensive calcification of bones and tissues follows (mainly affects the urinary system). Long extension disrupts the functioning of muscle and nerve tissues, increases blood coagulation and reduces the digestibility of zinc cells of bone tissue. The maximum daily safe dose is an adult from 1500 to 1800 milligrams.

Calcium products, mg / 100 g

Schorts 783.

Nettle 713.

Plantain big 412.

Sardines in oil 330

Wrushoid butders 289.

Rosehip dog 257.

Almond 252.

Plantain Lancetolist. 248.

Forest nut 226.

Cress Salad 214

Soybean Beans Dry 201

Children up to 3 years old - 600 mg.

Children from 4 to 10 years old - 800 mg.

Children from 10 to 13 years old - 1000 mg.

Teens from 13 to 16 years old - 1200 mg.

Youth from 16 and older - 1000 mg.

Adults from 25 to 50 years - from 800 to 1200 mg.

Pregnant and breastfeeding women - from 1500 to 2000 mg.

Conclusion

Calcium is one of the most common elements on Earth. In nature, it is a lot of: from calcium salts, mountain ranges and clay rocks are formed, it is in sea and river water, it is included in the composition of plant and animal organisms.

Calcium is constantly surrounding citizens: almost all major building materials - concrete, glass, brick, cement, lime - contain this element in significant quantities.

Naturally, possessing such chemical properties, calcium cannot be in nature in a free state. But calcium compounds - and natural and artificial - gained paramount importance.

Bibliography

1.Radic.: Knunyantz I. L. (ch. Ed.) Chemical encyclopedia: in 5 tons. - Moscow: Soviet Encyclopedia, 1990. - T. 2. - P. 293. - 671 with

2.Doronin. N. A. Calcium, Goshimzdat, 1962. 191 p. With ill.

.Dotsenko V.A. - Therapeutic and preventive nutrition. - Vopr. Power, 2001 - N1-C.21-25

4.Bilezikian J. P. Calcium and Bone Metabolism // In: K. L. Becker, ED.

5.MK Karapetyanz, S.I. Drakin - general and inorganic chemistry, 2000. 592 pp from Ill.

Calcium is located in the fourth large period, the second group, the main subgroup, the sequence number of the element - 20. According to the periodic table of Mendeleev, the atomic weight of calcium is 40.08. The formula of the highest oxide - SAO. Calcium has a Latin name calcium.therefore, the symbol of an element of an element is.

Calcium characteristic as a simple substance

Under normal conditions, calcium is a silver-white metal. Having high chemical activity, the element is capable of forming many connections of different classes. The element represents the value for technical and industrial chemical synthesis. Metal is widespread in the earth's crust: its share is about 1.5%. Calcium refers to a group of alkaline earth metals: when dissolved in water, it gives alkali, but in nature it is found in the form of multiple minerals and. Sea water contains calcium in large concentrations (400 mg / l).

Pure sodium

Calcium characteristics depend on the structure of its crystal lattice. It has two types of element: cubic granet center and volume centric. Type of communication in the molecule - metal.

Natural sources of calcium:

apatity;
alabaster;
gypsum;
calcite;
fluorite;
dolomite.

Physical properties of calcium and methods for producing metal

Under normal conditions, calcium is in a solid aggregate state. Metal melts at 842 ° C. Calcium is a good electric and thermal conductory. When heated, it passes first into liquid, and then into a vapor state and loses metal properties. Metal is very soft and cut into a knife. Bigs at 1484 ° C.

Under the pressure of calcium loses metal properties and the ability to electroplating. But then the metal properties are restored and the properties of the superconductor are manifested, several times larger in its indicators the rest.

Calcium did not fail for a long time to receive without impurities: due to high chemical activity, this element does not occur in nature in its pure form. The element was opened at the beginning of the XIX century. Calcium as a metal for the first time synthesized the British chemist Gemphri Davy. The scientist discovered the features of the interaction of melts of solid minerals and electric shock salts. Nowadays, electrolysis of calcium salts (mixtures of calcium and potassium chlorides, a mixture of fluoride and calcium chloride) remains the most relevant method of producing metal. Calcium is also removed from its oxide using aluminothermia - common in metallurgy method.

Calcium chemical properties

Calcium is an active metal that comes into many interactions. Under normal conditions, it easily reacts, forming appropriate binary compounds: with oxygen, halogens. Click to learn more about calcium connections. When heated calcium reacts with nitrogen, hydrogen, carbon, silicon, boron, phosphorus, gray and other substances. In the open air, it instantly interacts with oxygen and carbon dioxide, so it is covered with a gray raid.

Burly reacts with acids, while sometimes flammable. In calcium salts, there is an interesting properties. For example, cave stalactites and stalagmites are calcium carbonate, gradually formed from water, carbon dioxide and bicarbonate as a result of the processes inside groundwater.

Due to the high activity in the usual state of calcium is stored in laboratories in dark hermetic glassware under the layer of paraffin or kerosene. High-quality calcium ion reaction - flame painting in a saturated brick-red color.

Calcium paints flames in red

It is possible to identify the metal in the composition of the compounds by insoluble sediments of some element salts (fluoride, carbonate, sulfate, silicate, phosphate, sulfite).

Calcium water reaction

Calcium is stored in banks under the layer of protective fluid. To carry out that demonstrates how the water and calcium reaction occurs, it is impossible to simply get the metal and cut the desired piece from it. Metal calcium in laboratory conditions are easier to use in the form of chips.

If there is no metal chips, and there are only large calcium pieces in the bank, passage or hammer will be required. The finished piece of calcium of the desired size is placed in a flask or a glass with water. Calcium chips put in the dishes in the gauze bag.

Calcium lowers at the bottom, and hydrogen isolation begins (first in the place where the fresh ohloh is located). Gradually, gas is released from the calcium surface. The process resembles a stormy boil, at the same time a precipitate of calcium hydroxide (extinguished lime) is formed.

Hazeling

A piece of calcium pops up, praised by bubbles of hydrogen. After about 30 seconds, calcium is dissolved, and water from the formation of the hydroxide suspension becomes muddy white. If the reaction is not carried out in a glass, but in the tube, it is possible to observe heat selection: the test tube quickly becomes hot. The calcium reaction with water does not end with a spectacular explosion, but the interaction of two substances flows rapidly and looks like spectacular. Experience is safe.

If the bag with the remaining calcium is removed from the water and hold on the air, then after a while, as a result of the continuing reaction, strong heating and the remaining in Marla will boil. If part of the speedy solution is filtering through a funnel into a glass, then when passing through a solution of carbon monoxide CO₂ is a precipitate. For this, carbon dioxide does not need - you can blow the exhaled air into the solution through a glass tube.

Electricity 1.00 (Pauling Scale) Electrode potential −2,76 Oxidation degree 2 Ionization energy
(first electron) 589.4 (6,11) KJ / Mol (eV) Thermodynamic properties of a simple substance Density (with n. Y.) 1.55 g / cm³ Melting temperature 1112 K; 838,85 ° C. Boiling temperature 1757 K; 1483,85 ° C. UD. Warm melting 9.20 kJ / mol UD. Heat evaporation 153.6 kJ / mol Molar heat capacity 25.9 J / (k · mol) Molar volume 29.9 cm ³ / mol Crystal lattice of a simple substance Structure of grille Cubic granet center Grid parameters 5,580 Debaic temperature 230 Other features Thermal conductivity (300 K) (201) W / (M · K) Cas 7440-70-2 Emisy spectrum

History and origin of the name

The name of the element comes from the lat. Calx (in the Parentine calcis.) - "Lime", "soft stone". It was proposed by the English chemist of Davy Gemphri, in 1808. allocated metal calcium with electrolytic method. DEVI subjected the electrolysis mixture of wet gasheny lime with on a platinum plate, which was an anode. The cathode served as a platinum wire, immersed in liquid. As a result of electrolysis, calcium amalgam was obtained. Heat out from her mercury, Davy got a metal called Calcium.

Isotopes

Calcium is found in nature in the form of a mixture of six isotopes: 40 CA, 42 CA, 43 CA, 44 CA, 46 CA and 48 CA, among which the most common - 40 CA is 96.97%. Calcium cores contain a magic number of protons: Z. \u003d 20. Isotopes 40
20 CA20.
and 48
20 CA28.
There are two of the five in nature in nature twice magic nuclei.

Of the six natural isotopes of calcium, five are stable. The sixth isotope 48 Ca, the greatest of six and very rare (its isotopic prevalence is only 0.187%), is experiencing a double beta decay with a half-life (4.39 ± 0.58) ⋅10 19 years.

In rocks and minerals

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

Most of the calcium is contained as part of silicates and aluminosilicates of various rocks (granites, gneisses, etc.), especially in the field Plug - Animal CA.

Calcite CaCo 3, CASO 4 Anhydrite, Caso 4 Alabaster Caso 4 · 0.5h 2 O and Caso 4 · 2H 2 O, Fluorite CaF 2, Apatite Ca 5 (PO 4) 3 (F, CA 5 (PO 4) 3 (F, CL, OH), dolomite MGCO 3 · Caco 3. The presence of calcium and magnesium salts in natural water is determined by its rigidity.

A sedimentary breed consisting mainly of hikingrystalline calcite - limestone (one of its varieties - chalk). Under the action of regional metamorphism, limestone is transformed into marble.

Migration in the earth's crust

In the natural migration of calcium, a "carbonate equilibrium" plays a significant role associated with a reversible reaction of the interaction of calcium carbonate with water and carbon dioxide to form a soluble hydrocarbonate:

C A CO 3 + H 2 O + CO 2 ⇄ C A (HCO 3) 2 ⇄ C A 2 + + 2 HCO 3 - (\\ DisplayStyle (\\ Mathsf (Caco_ (3) + H_ (2) O + CO_ (2 ) \\ rightleftarrows Ca (HCO_ (3)) _ (2) \\ rightleftarrows Ca ^ (2 +) + 2HCO_ (3) ^ (-))))

(Equilibrium is shifted to the left or right depending on the concentration of carbon dioxide).

Biogenic migration plays a huge role.

In the biosphere

Calcium compounds are almost in all animal and vegetable tissues (see below). A significant amount of calcium is included in living organisms. Thus, hydroxyapatite Ca 5 (PO 4) 3 OH, or, in another record, 3CA 3 (PO 4) 2 · Ca (OH) 2 is the base of the bone vertebral tissue, including a person; Caco 3 calcium carbonate consists of sinks and shells of many invertebrates, egg shell, etc. in alive tissues of man and animals 1.4-2% Ca (by mass fraction); In the human body weighing 70 kg calcium content - about 1.7 kg (mainly in the composition of the intercellular substance of bone tissue).

Obtaining

Free metal calcium is obtained by the electrolysis of the melt consisting of CaCl 2 (75-80%) and KCl or from CaCl 2 and CAF 2, as well as aluminothermic recovery of Cao at 1170-1200 ° C 4 C A O + 2 A L → C A A L 2 O 4 + 3 C A (\\ DisplayStyle (\\ Mathsf (4CAO + 2AL \\ RIGHTARROW CAAL_ (2) O_ (4) + 3CA)))

Physical properties

Calcium metal exists in two allotropic modifications. Up to 443 ° C stable α -CA with cubic grazenarized grille (parameter but \u003d 0.558 nm), above stable β -CA. with cubic volume-centered type grid α -fe (parameter a. \u003d 0.448 nm). Standard enthalpy Δ H 0 (\\ DisplayStyle \\ Delta H ^ (0)) Transition α → β This is 0.93 kJ / mol.

With a gradual increase in pressure, it begins to show the properties of a semiconductor, but does not become a semiconductor in the full sense of the word (metal is also not). With a further increase in pressure returns to the metallic state and begins to show superconducting properties (the temperature of superconductivity is six times higher than that of mercury, and far exceeds the conductivity all other elements). The unique behavior of calcium seems to be largely on strontium (that is, parallels are preserved in the periodic system).

Chemical properties

In the number of standard calcium potentials is located to the left of hydrogen. Standard electrode potential CA 2+ / CA 0.84 V pair, so calcium actively reacts with water, but without ignition:

C a + 2 H 2 O → C A (O H) 2 + H 2. (\\ displayStyle (\\ Mathsf (Ca + 2H_ (2) O \\ Rightarrow Ca (OH) _ (2) + H_ (2) \\ Uparrow.)))

The presence of a dissolved calcium bicarbonate in water largely determines the time rigidity of water. It is called it because, when boiling water, the bicarbonate is decomposed, and Saci 3 falls into the precipitate. This phenomenon leads, for example, to the fact that in the teapot, scale is formed.

Application

The main use of metal calcium is the use of it as a reducing agent when producing metals, especially nickel, copper and stainless steel. Calcium and its hydride are also used to obtain hardly recoverable metals, such as chrome, thorium and uranium. Calcium alloys with lead are used in some types of batteries and in the production of bearings. Calcium granules are also used to remove traces of air from electrovacuum instruments. Pure metallic calcium is widely used in metalothermia when obtaining rare-earth elements.

Calcium is widely used in metallurgy for deoxidation steel along with aluminum or combined with it. Essay treatment with calcium-containing wires occupies the leading position due to the multi-meter calcium effect on the physicochemical state of the melt, macro and microstructure of the metal, the quality and properties of metal products and is an integral part of the steel production technology. In modern metallurgy for entering the calcium melt, an injection wire is used, which represents calcium (sometimes silicocalcations or aluminocalities) as a powder or extruded metal in a steel shell. Along with the deoxidation (removal of oxygen dissolved in steel), the use of calcium allows us to be obtained by nature, the composition and form of non-metallic inclusions that are not destroyed in the course of further technological operations.

Isotope 48 CA is one of the efficient and consumable materials for the production of superhane elements and the opening of new elements of the Mendeleev table. This is due to the fact that calcium-48 is twice the magic core, so its stability allows it to be sufficiently neutron enhancement for the light kernel; In the synthesis of superheassed nuclei, excess neutrons are needed.

Biological role

The concentration of calcium in the blood due to its importance for a large number of vital processes is precisely regulated, and with proper nutrition and sufficient consumption of low-fat dairy products and vitamin D deficiency does not occur. The long-term deficiency of calcium and / or vitamin D in the diet leads to an increase in the risk of osteoporosis, and rickets causes in infancy.

Notes

Grainll solidity 200-300 MPa
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Mikhailov G. G., Chernova L. A. Thermodynamic analysis of deoxidation processes with calcium and aluminum (Rus) // Electrometallurgy: Magazine. - 2008. - March (No. 3). - P. 6-8.
Shell Model Of Nucleus
Institute of Medicine (US) COMMITTEE TO REVIEW DIETARY REFERENCE INTAKES FOR VITAMIN D AND CALCIUM; ROSS AC, TAYLOR CL, YAKTINE AL, DEL VALLE HB, EDITORS (2011).

Introduction

Chemistry is a science of substances, their structure, properties and interconcesses.

Chemistry is closely related to other natural sciences: physics, biology, geology. Many sections of modern science emerged at the junction of these sciences: physical chemistry, geochemistry, biochemistry.

A new specialty in the system of chemical disciplines called "Classification and certification of goods based on chemical composition" was founded in 1997 by Uzbek scientists I.R. Askarov and TT Riscus. Important in the formation of this new chemical discipline was the results of scientific research conducted by such Uzbek scientists as A.A. Ibrahimov, G.Kh. Hamrakulov, MA Rakhimjanov, M.Yu. Isakov, KM Karimkulov, O.A. Tashpulatov, A.A. Namaz, B.Ya. Abduganiev, S.M. Mirkomlov, O. Kulimov, N.Kh. Tukhtaboev and others.

Calcium - As an alkaline earth metal, one of the most important elements on Earth.

Calcium is very important both for humans and for animals and plants.

Naturally, possessing such chemical properties, calcium cannot be in nature in a free state. But calcium compounds - and natural and artificial - gained paramount importance.

Ka? ltri - element of the main subgroup of the second group, the fourth period of the periodic system of chemical elements D.I. Mendeleev, with atomic number 20, therefore, the core of the calcium atom has 20 positive charges formed by 20 protons; Number of neutrons in the kernel 40 - 20 \u003d 20. 20 electrons neutralizing the charge of the nucleus are located on four levels of energy. Relative atomic weight 40.078 (4). Denotes symbol CA. (Lat. Calcium).

1. History of opening

The name of the element comes from the lat. CALX (in the Parental Calcis Padder) - "Lime", "Soft Stone". It was proposed by the English chemist Humphrey Davy, in 1808 we allocated metal calcium with electrolytic method. Davy subjected the electrolysis mixture of wet gashenny lime with mercury oxide HG 2O on the platinum plate, which was an anode. The cathode served as a platinum wire, immersed in liquid mercury. As a result of electrolysis, calcium amalgam was obtained. Heat out from her mercury, Davy got a metal called Calcium.

calcium Chemical Connection

2. Finding in nature

Due to the high chemical activity of calcium in free form in nature, it is not found.

Calcium accounts for 3.38% of the mass of the earth's crust (5th place in prevalence after oxygen, silicon, aluminum and iron). The content of the element in sea water is 400 mg / l.

Most of the calcium is contained in silicates and aluminosilicates of various rocks (granites, gneissions, etc.), especially in Field Plug - Animal CA.

In the form of sedimentary calcium compounds are presented with chalk and limestones consisting mainly of calcite mineral (CACO 3). Crystalline form of calcite - marble - occurs in nature much less often.

Calcium minerals are quite widespread as:

calcite, limestone, marble, chalk Caco3 ,

angidrit Caso4 ,

caso4 Alabaster · 0.5h. 2O.

gypsum Caso4. · 2h. 2O,

fluorite CAF2. ,

phosphites and Apatity CA 3(PO. 4)2(F, CL, OH),

dolomite MGCO3. · Caco. 3.

The presence of calcium and magnesium salts in natural water is determined by its rigidity.

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

Fig. 1. Calcium deposits in salty glances

Calcium compounds are in almost all animal and vegetable tissues. A significant amount of calcium is included in living organisms. So, hydroxyapatite Ca 3(PO. 4)2Oh, or, in another record, 3CA 3(PO. 4)2· Ca (OH) 2 - the basis of vertebrate bone tissue, including a person; Caco calcium carbonate 3 Consist the shells and shells of many invertebrates, egg shell, etc. in the living tissues of man and animals 1.4-2% Ca (by mass fraction); In the human body weighing 70 kg calcium content - about 1.7 kg (mainly in the composition of the intercellular substance of bone tissue).

. Obtaining

In the calcium industry is obtained in two ways:

Heating the briquetted mixture of SAO and AL powder at 1170-1200 ° C in vacuum 0.01 - 0.02 mm. RT. st.; Reaction items:

Sao + 2Al \u003d 3CAO · Al2 O. 3 + 3CA.

Calcium pairs are condensed on a cold surface.

Electrolysis of melt sasl 2 (75-80%) and KSL with a liquid copper-calcium cathode are prepared with an alloy Cu - Ca (65% Ca), from which calcium is distilled off at a temperature of 950 - 1000 ° C in vacuum 0.1 - 0.001 mm. RT. Art. or from (6 parts) CACL 2 and (1 part) CAF2.

It also developed a method for obtaining calcium thermal dissociation of calcium carbide CAC2 .

4. Physical properties

The appearance of a simple substance

Rice2. Moderately solid, silver-white metal

Name, symbol, number

Ka ? Ltria / Calcium (CA), 20

Atomic mass (molar mass)

40.078 a. e. m. (g / mol)

Electronic configuration

Radius atom

Covalent radius

Ion radius

Electricity

1.00 (Pauling Scale)

Electrode potential

Oxidation degree

Ionization energy (first electron)

589.4 (6,11) KJ / Mol (eV)

Density (with n. Y.)

1.55 / cm³

Melting temperature

842 O. FROM

Warm melting

9.20 kJ / mol

Heat evaporation

153.6 kJ / mol

Molar heat capacity

25.9 J / (k · mol)

Molar volume

29.9 cm³ / mole

Structure of grille

cubic granet center

Grid parameters

Debaic temperature

Thermal conductivity

(300 K) (201) W / (M · K)

Simple substance calcium - Soft, chemically active silver-white metal-white metal.

Calcium metal exists in two allotropic modifications. Up to 443 ° C is stable? -CA with a cubic grazenarized grid (parameter A \u003d 0.558 nm), above stable? -CA with a cubic volume-centered type? -Fe grid (parameter a \u003d 0.448 nm). Standard enthalpy transition? ? ? This is 0.93 kJ / mol.

Calcium is found in nature in the form of a mixture of six isotopes: 40CA, 42CA, 43CA, 44CA, 46CA and 48CA, among which the most common - 40CA is 96.97%.

. Chemical properties

Calcium is a typical tick-earth metal. Calcium chemical activity is high, but lower than heavily picked risen metals. It easily interacts with oxygen, carbon dioxide and air moisture, due to which the surface of metal calcium is usually dimly gloomy, therefore, the calcium laboratory is usually stored, as well as other closed-earth metals, in a tightly closed can under a layer of kerosene or liquid paraffin.

At the external energy level there are 2 electrons. In all connections, the degree of calcium oxidation is +2.

In the number of standard calcium potentials is located to the left of hydrogen.

Standard electrode potential CA CA 2+/ CA. 0 ? 2.84 V, so calcium actively reacts with cold water (with hot water the reaction proceeds more vigorously), but without ignition:

With active non-metals (oxygen, chlorine, bromine), calcium reacts under normal conditions:

CA + CL.2 CACL2

When the air is heated or in calcium oxygen flames and burns with a red flame with an orange tint.

With less active non-metals (hydrogen, boron, carbon, silicon, nitrogen, phosphorus, and other), calcium enters into interaction when heated, for example:

In addition to CA3P2 calcium phosphide, the calcium phosphides of CAR and SAR5 compositions are also known;

In addition to CA2SI calcium silicide, calcium silicides CASI, CA3SI4 and CASI2 are also known.

The flow of the above reactions is usually accompanied by the release of a large amount of heat.

Calcium restores less active metals from their oxides and halides

2CA + TiO.2 2Cao + Ti.

CA + TiCl2 2cacl.2 + TI

Most of the calcium compounds with non-metals are easily decomposed with water, for example:

Ion Ca2 + Besmevetn. When in the flame of soluble calcium salts, the flame is painted in brick-red.

. Application of metallic calcium

1. Metalothermia

Pure metallic calcium is widely used in metalothermia when obtaining rare metals.

2. Alloy doping

3. Nuclear fusion

Isotope 48CA is one of the efficient and consuming materials for the production of superhane elements and the opening of new elements of the Mendeleev table. This is due to the fact that calcium-48 is twice the magic core, so its stability allows it to be sufficiently neutron enhancement for the light kernel; In the synthesis of superheassed nuclei, excess neutrons are needed.

. Calcium compounds

1. Calcium oxideCao (Negane Lime, Lime Lime, Kiphel) White refractory substance.

Obtained in limestone or chalk roasting at high temperatures (above 900 o FROM):

CaCo.3 \u003d Cao + Co2

Calcium oxide reacts with water to the formation of gaughted lime and highlighting a large amount of heat:

Cao + H.2 O \u003d CA (OH)2 + Q.

2. Calcium hydroxideCA (OH) 2 - a strong base, a little soluble in water.

CA (OH) 2 Used in various types:

haired lime is a thin loose powder, "Pushonka", obtained by the action of water for the next Cao lime:

Cao + H.2 O \u003d CA (OH)2

The tough mixture of hazed lime with cement, water and sand is used in construction. When absorbing carbon dioxide from the air, this mixture solidifies:

CA (OH)2 + Co.2 \u003d Caco.3 + H.2 O.

lime Milk - This is a suspension of particles of Haired Lime CA (OH) 2 in lime water.

Used for blissing in construction, disinfection of tree trunks, in the sugar industry, for taking skin, to obtain chlorine lime.

lime water - saturated aqueous solution of Ca (OH) 2

The solution in air is purre due to the absorption of carbon dioxide from the air.

But with long-term transmission of carbon dioxide, the solution becomes

transparent due to the formation of soluble calcium bicarbonate:

CaCo.3 + Co.2 + H.2 O \u003d CA (HCO3 ) 2

In nature, this leads to the following processes. When a cold rain or river water, saturated with carbon dioxide, penetrates under the ground and falls on limestones, then their dissolution is observed, and the same places where water saturated with calcium bicarbonate goes to the surface of the Earth and heated by sunlight.

So in nature the transfer of large masses. As a result, huge failures may form underground, and beautiful stone "icicles" - stalactites and stalagmites are formed in the caves.

3. Bleaching powder- is a strong oxidant, the main component of which is salt Caocl 2Formed when interacting with dry hawed lime with chlorine:

CA (OH)2 + Cl.2 \u003d Caocl2 + H.2 O.

Chlorine lime is a white powder with a sharp odor, which in wet air under the action of carbon dioxide gradually decomposes, highlighting a chlorothic acid:

2caocl2 + Co.2 + H.2 O \u003d CaCo.3 + CaCl2 + 2hclo.

In the light of chlorothic acid decomposes:

2HCLO \u003d 2HCl + O2

Under action on chlorine lime of hydrochloric acid, chlorine is released:

Caocl2 + 2HCl \u003d CaCl2 + Cl.2 + H.2 O.

This is based on whitening and disinfectant properties of chlorine lime.

4. GypsumCaso. 4· 2h. 2O - Natural calcium mineral.

When heated to 150-180 ° C loses weights ¾ crystallization water and goes into alabaster or burned gypsum.

2Caso.4 * 2h.2 O 2CASO.4 * H.2 O + 3h.2 O.

When mixing with water, the alabaster quickly solidifies, turns again

2Caso.4 * H.2 O + 3h.2 O 2CASO.4 * 2h.2 O.

This feature of the gypsum is used to make the casting forms and blinds from various items, as well as as a binder in construction for plastering and others. Gypsum is widely used in medicine for the manufacture of gypsum bandages.

When heating plaster at a temperature above 180 ° C, anhydrous gypsum (calcium anhydride, or dead gypsum) is formed, which is not capable of attaching water.

Caso.4 * 2h.2 O Caso.4 + H.2 O.

Calcium salts such as CaCl2 chloride, CABR2 bromide, CAI2 iodide and Ca nitrate (NO3) 2 are well soluble in water. Insoluble in water fluoride<#"justify">1. Hydride calcium

Calcium heating in hydrogen atmosphere<#"justify">2. Calcium oxide

CAO calcium oxide, as part of a solid solution of oxides of other pic-indoor metals<#"justify">3. Optical and laser materials

Calcium fluoride<#"justify">4. Calcium carbide

Calcium carbide<#"justify">Calcium oxide, both in free form and in the composition of ceramic mixtures, is used in the production of refractory materials.

7. Construction Materials<#"justify">Calcium compounds (mainly carbonate or hydrocarbonate) are used for coating electrodes in arc electrical welding. Calcium compounds are widely used to prepare fluxes for melting and welding metals.

9. Medicinal products<#"justify">Calcium compounds are widely used as an antihistamine.

·Calcium chloride<#"justify">. Biological role

Calcium - Common Macroelement<#"312" src="doc_zip16.jpg" />

Table 1. Calcium content in some food

Food Product Quantity Calcium content in this amount of product, Mallopole and Ground products Cheese - Swiss, Rierskaya 50 g. 493 Cheese - and solid form, Cheddar, Colby, Edak, Gaud 50 g. 353 Milk - whole, 2%, 1% fat content 1 glass / 250 ml 315 cream 1 cup / 250 ml 301 cheese mozzarella, adygei, cheese 50 269 yogurt - ordinary 1 cup / 175 ml 292 molio - dry, in powder 45 ml 159 ice cream 1/2 cup 93 cheese - Rustic, creamy 2%, 1% fatty (cottage cheese) 1/2 cup 87MMA, fish, poultry and other sardine products, with bones 8 small 153 salmon, bones, canned 1/2 banks (net weight 13 g.) 153 Almonds 1/2 cup 200 sesame 1/2 cups 100 beans - prepared (beans, blue beans, spotted beans) 1/2 cups 90 Soybean beans - cooked 1 cup 175 chicken - fried 90 g. 13 beef - fried 90g 7Hleb and grain Round bun with bran 1/35. 50 bread - white and wheat 1 piece / 30 g. 25fruits, and vegetables of broccoli - in raw form 1/2 Cups 38 Oranges 1 medium size / 180 g. 52 Middle Size Bananas / 175g 10 Salad 2 large sheet 8 Dried figs 10 270 Combined dishes with milk soup, soup in the form of a chicken cream, mushrooms, tomatoes and broccoli 1 cup / 250 ml 189 boiled Canned beans 1 cup / 250 ml 169

Conclusion

Calcium is one of the most common elements on Earth.

Calcium was opened by the English chemist Humphrey Davy in 1808. He allocated a metal calcium with electrolytic pathway from a mixture of hazed lime and mercury oxide.

In 1789, A. Lavoisier proposed that lime, magnesia, barite, alumina and silica - compound substances.

There is a lot of nature in nature. Free form does not occur. Mountains and clay rocks are formed from calcium salts, it is in sea and river water. It is part of such minerals like marble (chalk), alabaster, plaster, fluorite, phosphite, apatite and dolomites.

Calcium is also part of living organisms - in all animals and vegetable tissues, and most importantly calcium is part of the bone tissue of a person.

Calcium is obtained in two ways:

1.Heating the mixture of oversized lime and aluminum.

2.The second method, as well as all metals, electrolysis, in this case, the CaCl2 and KCl melt with a liquid copper-calcium cathode.

Calcium is a soft chemically active alkaline earth metal, silver-white.

Calcium - Typical Picked Square Metal<#"justify">1.I. Askarov K. Gopirov "Fundamentals of Chemistry" State Scientific Publishing House "Uzbekistan Milly Encyclopedia" Tashkent - 2013 p. 347

2.I.R. Asqarov sh.h. Abdullaev o. sh. Abdullaev "Kimyo - Oily O`quv Yurtlariga Kiruvchilar Uchun" "Tafakkur" Nashriyoti Toshkent - 2013

3.N.L. Glinka "General Chemistry" Moscow - 1988

."Schoolchild Certificate" Bishkek - 2000 pp. 152-156

.G.P. Khomchenko "Chemistry - Universal Collection" Moscow New Wave Publisher of Deaders - 2008 p. 301-306

.F.G. Felbdman G.E. Rudzitis "Chemistry 9" Moscow "Enlightenment" - 1990 p. 127-132

."Universal Directory" Moscow - 2006 p. 648-651

8.www.google.com //ru.wikipedia.org // wiki // Calcium.

.www.google.co.ru //otherreferats.allbest.ru // Chemistry.

.www.google.com //medwiki.org.ua // Article // Calcium.

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Introduction

Calcium properties and application

1 Physical Properties

2 Chemical properties

3 Application

Calcium production

1 Electrolytic calcium and its alloys

2 Thermal receipt

3 Vacuum thermal method of obtaining calcium

3.1 Aluminothermic method of calcium recovery

3.2 Silicothermal Calcium Recovery Method

Practical part

Bibliography

Introduction

Chemical element II group of the periodic Mendeleev system, atomic number 20, atomic weight 40.08; Silver-white light metal. The natural element represents a mixture of six stable isotopes: 40CA, 42CA, 43CA, 44CA, 46CA I. 48CA, of which the most common 40 Ca (96, 97%).

CA - limestone, marble, gypsum (as well as lime - limestone firing product) Already in ancient times were used in construction business. Until the end of the 18th century, chemists considered lime with a simple body. In 1789, A. Lavauzier suggested that lime, magnesia, barite, alumina and silica - compound substances. In 1808, Davy, exposing the electrolysis with a mercury cathode, a mixture of a wet hazed lime with mercury oxide, prepared the Amalgam Ca, and sway from it, got a metal, called "Calcium" (from Lat. Calx, born Calcis - Lime) .

Calcium ability to bind oxygen and nitrogen allowed it to use it to purify inert gases and as a heter (getter - a substance that serves to absorb gases and creating a deep vacuum in electronic devices.) In vacuum radio equipment.

Calcium is used in copper, nickel metallurgy, nickel, special steels and bronze; They associate harmful impurities of sulfur, phosphorus, excess carbon. For the same purposes, calcium alloys with silicon, lithium, sodium, boron, aluminum are used.

In the calcium industry is obtained in two ways:

) Heating the briquetted mixture of SAO and Powder AL at 1200 ° C in vacuum 0.01 - 0.02 mm. RT. st.; Reaction items:

SAO + 2AL \u003d 3CAO · Al2O3 + 3CA

Calcium pairs are condonsigned on a cold surface.

) The electrolysis of the Melt Sasl2 and KSL with a liquid copper-calcium cathode is prepared with an alloy Cu - Ca (65% CA), from which calcium is distilled off at a temperature of 950 - 1000 ° C in vacuum 0.1 - 0.001 mm.T.

) A method of obtaining calcium is also developed by the thermal dissociation of calcium carbide CAC2.

Calcium is very common in nature in the form of various compounds. In the earth's crust, he ranks fifth, accounted for 3.25%, and most often occurs in the form of limestone CACO 3, Dolomite CaCo 3· Mg Co. 3, Caso gypsum 4· 2h. 2O, phosphorite CA 3(PO. 4)2 and Platical Plove Caf 2, not counting the significant share of calcium as part of silicate rocks. In seawater, an average of 0.04% (weight) calcium is contained.

In this course, the properties and use of calcium are studied, as well as the theory and technology of vacuum thermal methods of obtaining it is considered in detail.

. Calcium properties and application

.1 physical properties

Calcium is a silver-white metal, but in the air dumps due to the formation of oxide on its surface. This plastic metal is harder lead. Crystal cell ?-forms Ca (sustainable at normal temperature) granetantrized cubic, and \u003d 5,56 Å . Atomic radius 1.97 Å , ion radius Ca 2+, 1,04Å . Density 1.54 g / cm 3(20 ° C). Above 464 ° C resistant hexagonal ?-the form. TPL 851 ° C, TKIP 1482 ° C; Temperature ratio of linear extension 22 · 10 -6 (0-300 ° C); thermal conductivity at 20 ° C 125.6 W / (M · K) or 0.3 kal / (cm · s · ° C); Specific heat capacity (0-100 ° C) 623.9 J / (kg · k) or 0.149 Cal / (g · ° C); Specific electrical resistance at 20 ° C 4.6 · 10 -8 Om · m or 4,6 · 10 -6 ohm · cm; Temperature coefficient of electrical resistant 4.57 · 10-3 (20 ° C). Elastic module 26 Gn / m 2 (2600 kgf / mm 2); Tensile strength of 60 mn / m 2 (6 kgf / mm 2); Elastic limit 4 mn / m 2 (0.4 kgf / mm 2), yield strength 38 MN / m 2 (3.8 kgf / mm 2); relative elongation 50%; Brinell Hardness 200-300 MN / M 2 (20-30 kgf / mm 2). Calcium is quite high purity plastic, well pressed, rolled and treatable cutting.

1.2 Chemical properties

Calcium - active metal. So under normal conditions, it easily interacts with air oxygen and halogens:

Ca + O. 2 \u003d 2 CAO (calcium oxide) (1)

Sa + in 2 \u003d Savr. 2 (Calcium Bromide). (2)

With hydrogen, nitrogen, gray, phosphorus, carbon and other non-metals calcium reacts when heated:

CA + N. 2 \u003d San. 2 (calcium hydride) (3)

CA + N. 2 \u003d SA 3N. 2 (calcium nitride) (4)

CA + S \u003d SAS (calcium sulfide) (5)

Sa + 2 p \u003d sa 3R 2 (Calcium phosphide) (6)

CA + 2 C \u003d CAC 2 (calcium carbide) (7)

With cold water calcium interacts slowly, and with hot - very energetic, giving a strong base of sa (he) 2 :

Ca + 2 N 2O \u003d sa (he) 2 + N. 2 (8)

Being an energetic reducing agent, calcium can take oxygen or halogens from oxides and halides of less active metals, i.e. possesses reducing properties:

CA + NB. 2O5. \u003d Sao + 2 NB; (nine)

CA + 2 NBSL 5 \u003d 5 sasl2. + 2 NB (10)

Calcium is vigorously interacting with acids with hydrogen release, reacts with halogens, with dry hydrogen with the formation of hydride San 2. When heated calcium with graphite, CAC carbide is formed 2. Calcium is obtained by electrolysis of molten CACL 2 or aluminothermic recovery in vacuum:

6SAO + 2AL \u003d 3CA + 3CAO · AL2 ABOUT 3 (11)

Pure metal is used to restore CS, RB, CR, V, ZR, TH, U, U to metals, for deoxidation steels.

1.3 Application

Calcium finds all increasing. Application in various industries. Recently, it has gained great importance as a reducing agent in obtaining a number of metals.

Pure metal. Uranium is obtained by the restoration of metallic calcium of uranium fluoride. Calcium or hydrides can be restored by titanium oxides, as well as zirconium oxides, thorium, tantalum, niobium, other rare metals.

Calcium is a good deoxidizer and a degasser when producing copper, nickel, chromonicelie alloys, special steels, nickel and tin bronze; It removes sulfur from metals and alloys, phosphorus, carbon.

Calcium forms with bismuth refractory compounds, so it is used to purify lead from bismuth.

Calcium is added to various light alloys. It helps to improve the surface of the ingots, fine-grainedness and decrease in oxidation.

Much propagation contains calcium bearing alloys. Lead alloys (0.04% Ca) can be used for the manufacture of cable shells.

The technique uses antifriction alloys calcium with lead. Calcium minerals are widely used. So, limestone is used in the production of lime, cement, silicate brick and directly as building material, in metallurgy (flux), in the chemical industry for the production of calcium carbide, soda, caustic soda, chlorine lime, fertilizer, in the production of sugar, glass.

The chalk, marble, Icelandic swipe, plaster, fluorite, etc. have practical importance. Due to the ability to bind oxygen and nitrogen of calcium or calcium alloys with sodium and other metals, used for cleaning noble gases and as a getter in vacuum radio equipment. Calcium is also used to obtain hydride, which is a source of hydrogen in the field.

2. Obtaining calcium

There are several methods for producing calcium, it is electrolytic, thermal, vacuum thermal.

.1 electrolytic obtaining calcium and its alloys

The essence of the method lies in the fact that the cathode originally concerns the molten electrolyte. In the place of contact, a well-wetting cathode is formed with a liquid metal drop, which, with a slow and uniform raising of the cathode, is displayed with it from the melt and freezes. At the same time, the frozen drop is covered with a solid electrolyte film that protects the metal from oxidation and nitriding. By continuous and cautiously lifting the calcium cathode is pulled out into the rods.

2.2 Thermal receipt

calcium chemical electrolytic thermal

· Chloride process: The technology consists of melting and dehydrating calcium chloride, melting lead, producing a double leaf alloy - sodium, obtaining a triple alloy lead - sodium - calcium and dilution of the triple alloy lead after removal of salts. Calcium chloride reaction flows according to the equation

CACL 2 + Na. 2PB. 5 \u003d 2NACL + PBCA + 2PB (12)

· Carbide process: The basis of obtaining lead-calcium alloy is the reaction between calcium carbide and molten lead according to the equation

CAC. 2 + 3PB \u003d PB3 CA + 2C. (13)

2.3 Vacuum thermal method of obtaining calcium

Raw materials for vacuum thermal fashion

The raw material for the thermal recovery of calcium oxide is the lime obtained by limestone firing. The basic requirements for raw materials are as follows: Lime must be as cleaner and contain a minimum of impurities capable of restoring and moved to metal along with calcium, especially alkali metal and magnesium. The limestone firing should be made until the carbonate decomposition must be made, but not before it sintering, since the redundancy of the sintered material is lower. The burned product must be protected from absorption of moisture and carbon dioxide to absorb them, the allocation of which during restoration reduces the process indicators. The firing technology of limestone and the processing of the burnt product is similar to the processing of dolomite for the silicothermic method of producing magnesium.

.3.1 aluminothermic method of calcium recovery

In the diagram of the temperature dependence of the change in the free energy of the oxidation of a number of metals (Fig. 1) it can be seen that calcium oxide is one of the most durable and difficult to be recovered oxides. It cannot be restored by other metals in the usual way - with relatively low temperature and atmospheric pressure. On the contrary, calcium itself is an excellent reducing agent of other difficult to restore compounds and a deoxidizer for many metals and alloys. Restoration of calcium oxide carbon is generally impossible due to calcium carbides. However, due to the fact that calcium has a relatively high elasticity of steam, its oxide can be restored in vacuum aluminum, silicon or their alloys according to the reaction

Cao + Me? CA + MEO (14).

Practical application While there was only an aluminothermic method for obtaining calcium, since it is much easier to restore sao aluminum than silicon. On the issue of chemical restoration of calcium oxide aluminum there are different views. L. Pidgen and I. Etkinson believe that the reaction proceeds with the formation of calcium mono aluminate:

Saa + 2АL \u003d saa · al 2O3. + 3As. (fifteen)

V. A. Pzuhin and A. Ya. Fisher indicate that the process comes with the formation of three-killy aluminate:

Saa + 2АL \u003d 3SAO · Al 2O. 3 + 3As. (sixteen)

According to A. I. Vozyitsky, the predominant in the reaction is the formation of a five-fiscal three aluminum:

Sao + 6Al \u003d 5SAO · 3Al 2O3. + 9As. (17)

The newest studies, A. Y. Thai and A. I. Viozyitsky found that the aluminothermic calcium recovery proceeds stepwise. Initially, calcium is accompanied by the formation of ZSAO · AI 2O. 3which then reacts with calcium oxide and aluminum with the formation of ZSAO · 3AI 2O. 3. The reaction proceeds from the following scheme:

Sao + 6Al \u003d 2 (3SAO · Al 2O. 3) + 2SAO + 2Al + 6s

(3So · Al 2O. 3) + 2SAO + 2Al \u003d 5SAO · 3Al 2O. 3+ 3S.

Cao + 6A1 \u003d 5SAO · 3Al 2O. 3+ 9As.

Since the reduction of oxide occurs with the release of vapor calcium, and the remaining reaction products are in a condensed state, it is possible to easily separate and condense it in the cooled furnace sections. The basic conditions necessary for vacuum thermal recovery of calcium oxide are high temperature and low residual pressure in the system. The following is the dependence between the temperature and equilibrium elasticity of calcium vapor. Free reaction energy (17) calculated for temperatures 1124-1728 ° K is expressed

F. T. \u003d 184820 + 6.95T-12.1 T LG T.

Hence the logarithmic dependence of the equilibrium elasticity of a pair of calcium (mm Hg. Art.)

LG p \u003d 3.59 - 4430 \\ t.

L. Pidgen and I. Etkinson determined experimentally equilibrium elasticity of a pair of calcium. A thorough thermodynamic analysis of the reaction of the reduction of calcium oxide aluminum was performed by I. I. Matveenko, which gave the following temperature dependences of the equilibrium pressure of calcium vapors:

LG P. CA (1) \u003d 8.64 - 12930 \\ T mm Hg.

LG P. CA (2) \u003d 8.62 - 11780 \\ T mm Hg.

LG P. Ca (3. )\u003d 8.75 - 12500 \\ T mm RT.st.

The calculated and experimental data are mapped to Table. one.

Table 1- The effect of temperature on the change in the equilibrium elasticity of calcium vapors in systems (1), (2), (3), (3), mm Hg.

Temperature ° Rejuvenated data in systems (1) (2) (3) (3 )1401 1451 1500 1600 17000,791 1016 - - -0,37 0,55 1,2 3,9 11,01,7 3,2 5,6 18,2 492,7 3,5 4,4 6,6 9,50,66 1,4 2,5 8,5 25,7

From the given data, it is clear that in the most favorable conditions there are interactions in systems (2) and (3) or (3 "). This meets observations, since in the balances of the accumulation of calcium oxide, the pile aluminum is dominated by pile aluminum and three-killy aluminate.

The data on equilibrium elasticity shows that the reduction of calcium oxide aluminum is possible at a temperature of 1100-1150 ° C. To achieve a practically acceptable reaction speed, the residual pressure in the system should be lower than the equilibrium p equal , i.e. it should be observed inequality equal \u003e R. oIST and the process should be carried out at temperatures of about 1200 °. Studies found that at a temperature of 1200-1250 °, high use (up to 70-75%) and low specific consumption of aluminum (about 0.6-0.65 kg per kg calcium) are reached.

According to the above-mentioned interpretation of the chemical process, the optimal composition is the charge, designed for education in the residue 5SAO · 3Al 2O. 3. To increase the degree of use of aluminum, it is useful to give some excess calcium oxide, but not too large (10-20%), otherwise it will adversely affect other process indicators. With an increase in the degree of grinding of aluminum from particles 0.8-0.2 mm to minus 0.07 mm (according to V. A. Pazukhin and A. Ya. Fisher), the use of aluminum in the reaction increases from 63.7 to 78%.

Aluminum use also affects the charge briquetting mode. The mixture of lime and powder aluminum should be briquetted without binders (in order to avoid the separation of gases in vacuo) at a pressure of 150 kg / cm 2. With lower pressures, the use of aluminum decreases due to the liquidation of molten aluminum in unnecessary porous briquettes, and at high pressures due to poor gas permeability. Fullness and recovery speed also depend on the density of the briquette laying in the retort. When laying them without gaps, when the gas permeability of the entire cage is small, the use of aluminum is significantly reduced.

Figure 2 - Calcium production scheme with a vacuum thermal method.

Aluminum-thermal technology technology

The technological scheme for the production of calcium by aluminotherum is shown in Fig. 2. A limestone is used as a raw material, as a reducing agent - an aluminum powder cooked from primary (better) or secondary aluminum. The aluminum applied as a reducing agent, as well as raw materials, should not contain impurities of easily volatile metals: magnesium, zinc, alkalis, etc., capable of evaporating and move to condensate. This must be taken into account when choosing brands of secondary aluminum.

According to the description of S. Lumis and P. Staf, in the United States at the New Ingland Farmer of Lime Co in Canaan (Connecticut), calcium is obtained by aluminothermal. It is used to lime the following typical composition,%: 97.5 SAO, 0.65 MGO, 0.7SIO 20.6 Fe. 2OZ + alose, 0.09 Na 2O + K. 2O, 0.5 rest. The burned product is grinding on the Rammond mill with a centrifugal separator, the thinness of the grinding is (60%) minus 200 mesh. As a reducing agent, aluminum dust is used in the production of aluminum powder. The baked lime from the closed bunkers and aluminum from the drums go to dosage scales and then into the mixer. After mixing the mixture briquetted with a dry way. At the mentioned plant, calcium is restored in retort furnaces, previously used to produce magnesium by a silicothermic method (Fig. 3). The furnaces are heated by generator gas. Each furnace has 20 horizontal retort from heat-resistant steel containing 28% of SG and 15% Ni.

Figure 3- Retown oven for calcium

Retort length 3 m, diameter 254 mm, wall thickness 28 mm. Recovery occurs in a heated portion of retort, and condensation in the cooled end protruding from speech. Briquettes are introduced into retort in paper bags, then condensers and retort are inserted. Air pumping is performed by mechanical vacuum pumps at the beginning of the cycle. Then connect diffusion pumps and the residual pressure is reduced to 20 MK.

Retorts are heated to 1200 °. After 12 hours. After loading, the retorts open and unload. The resulting calcium has the shape of a hollow cylinder from the dense mass of large crystals deposited on the surface of the steel sleeve. The main impurity in calcium is magnesium, which is restored primarily and is mainly concentrated in the layer adjacent to the sleeve. On average, the content of impurities is; 0.5-1% Mg, about 0.2% Al, 0.005-0.02% Mn, up to 0.02% N, other impurities - SI, PL, Zn, Ni, Si, Fe - occur within 0.005-0.04%. A. Yu. Takes and A.I. Viozytskyi to obtain calcium by aluminothermic method were used half-water electric vacuum furnace with coal heaters and reached the degree of use of aluminum 60%, the specific consumption of aluminum 0.78 kg, the specific consumption of the mixture, respectively, 4.35 kg and specific Electricity consumption 14 kW \\ h per 1 kg of metal.

The resulting metal, with the exception of magnesium impurities, was distinguished by relatively high purity. On average, the content of impurities in it was: 0.003-0.004% FE, 0.005-0.008% Si, 0.04-0.15% Mn, 0.0025-0.004% Cu, 0.006-0.009% N, 0.25% Al.

2.3.2 Silicothermal Recovery Method calcium

Very tempting is a silicothermic method; Restorener - ferrosilization, the reagent is significantly cheaper than aluminum. However, the silicothermic process is more difficult to implement than aluminothermal. Restoration of calcium oxide silicon proceeds according to the equation

Sao + Si \u003d 2SAO · SiO2 + 2s. (eighteen)

The equilibrium elasticity of the calcium pair calculated by the amounts of free energy is:

° C1300140015001600R, mm RT. St0,080,150,752.05

Consequently, in vacuum about 0.01 mm Hg. Art. The reduction of calcium oxide is thermodynamically possible at a temperature of 1300 °. Almost to ensure an acceptable speed, the process should be carried out at a temperature of 1400-1500 °.

A somewhat easier is the reaction of the reduction of calcium oxide with silicoaluminum, in which aluminum and silicon alloy serve as reducing agents. Experiments found that at first the restoration of aluminum prevails; And the reaction proceeds with the final formation of BSAO · 3Al 2OZ according to the scheme set out above (Fig. 1). The recovery of silicon becomes significant at a higher temperature when most of the aluminum reagent reacted; The reaction proceeds with the formation of 2CAO · SiO 2. In the summary form, the reaction of the reduction of calcium oxide with silicaluminia is expressed by the following equation:

mSI + P AL + (4M +2 ?) Sao \u003d M (2SAO · SiO 2) + ?n (5So · Al 2O3. ) + (2m +1, 5n) sa.

Research A. Yu. Thai and A. I. Viozyitsky found that calcium oxide is reduced by 75% ferrosilicia with a metal outlet 50-75% at a temperature of 1400-1450 ° in vacuum 0.01-0.03 mm RT. st.; Silicoaluminum containing 60-30% Si and 32-58% AL (the rest of the iron, titanium, etc.), restores calcium oxide with a metal outlet of about 70% at temperatures 1350-1400 ° in vacuum 0.01-0.05 mm RT . Art. The experiments in the semi-fed scale proved the principal possibility of obtaining calcium on the lime of ferrosilicide and silicoaluminum. The main hardware is the selection of the pillar in the conditions of this process of lining.

When solving this problem, the method can be implemented in industry. Calcium carbide decomposition Getting metal calcium decomposition calcium carbide

SAS2. \u003d CA + 2C

it should be attributed to promising ways. At the same time, graphite is obtained as a second product. V. Maudley, E. Moser, and V. Tredvell Calculating the free energy of calcium carbide formation from thermochemical data, received the following expression for elasticity of calcium steam over clean calcium carbide:

cA. \u003d 1.35 - 4505 \\ t (1124-1712 ° K),

lGP. cA. \u003d 6.62 - 13523 \\ T (1712-2000 ° K).

Apparently, the technical carbide calcium decomposes with significantly higher temperatures than this follows from these expressions. The same authors report the thermal decomposition of calcium carbide in compact pieces at 1600-1800 ° in vacuum 1 mm Hg. Art. The release of graphite was 94%, calcium was obtained in the form of a dense fly on the refrigerator. A. S. Mikulinsky, F. S. Morii, R. Sh. Shklar to determine the properties of graphite obtained by the decomposition of calcium carbide, heated the last in vacuum 0.3-1 mm Hg. Art. at a temperature of 1630-1750 °. The resulting graphite differs from the Assonian larger grains, greater electrical conductivity and less bulk weight.

3. Practical part

Daily magnesium lifting from an electrolyzer for strength of 100 ka accounted for 960 kg when nutritional nutrition with magnesium chloride. Voltage on the challenge of the electrolyzer 0.6 V. Determine:

)Current output on the cathode;

)The amount of chlorine obtained per day, provided that the current yield on the anode is equal to the current output on the CTODE;

)Daily fill MGCL 2 In the electrolyzer, provided that the loss of MgCl 2 they occur mainly with sludge and clutter. The amount of sludge 0.1 per 1T MG containing MGCL 2 in the alone 50%. The amount of 0.05 tons per 1T MG. The composition of the magnesium poured chloride,%: 92 MgCl2 and 8 NaCl.

.Determine the current outlet on the cathode:

m. etc \u003d I · ? · K. MG. · ?

?\u003d M. etc \\ I · ?· K. MG. \u003d 960000 \\ 100000 · 0.454 · 24 \u003d 0,881 or 88.1%

.Determine the number of CL obtained per day:

x \u003d 960000g \\ 24 g \\ mol \u003d 40000 mol

Transfer to volume:

x \u003d 126785.7 m3

3.a) find pure MGCL 2, For the production of 960 kg Mg.

x \u003d 95 · 960 \\ 24,3 \u003d 3753 kg \u003d 37.53 tons.

b) loss with sludge. From the composition of magnesium electrolyzers,%: 20-35 MgO, 2-5 Mg, 2-6 Fe, 2-4 SiO 20.8-2 TIO. 20.4-1.0 C, 35 MgCl2 .

kg - 1000 kg

m. sHL \u003d 960 kg - weight of the sludge per day.

Per day 96 kg sludge: 96 · 0.35 (MgCl2 with sludge).

c) Losses with vagas:

kg - 1000 kg

kg of sublims: 48 · 0.5 \u003d 24 kg MgCl 2 with vygami.

You need to pour MG:

33,6 + 24 \u003d 3810.6 kg MgCl2 in day.

Bibliography

Basics of metallurgy III

<#"justify"> Metallurgy Al and Mg. Vetyukov M.M., Chicklockov A.M.

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