The calcium is a chemical element, of symbol Ca and of Atomic number 20.

Calcium is a alkaline-earth Métal gray and soft. It is employed like reducing agent in the extraction of the Thorium, the Zirconium and the Uranium. This element which one never finds with the state of pure Substance in nature is the fifth most abundant element of the Earth's crust and is essential for the Organic matter.

Notable characteristics

Calcium can be produced by electrolysis of the fluoride of calcium but more usually by Réduction vacuum of the Chaux (CAD) by powder of Aluminum.

It burns with a flame yellow-red; exposed to the air sec it forms a white protective coating of oxide and nitride. It reacts violently with the water of which it moves the Hydrogène and then forms Hydroxyde of calcium Ca (OH) 2.

Physical applications of calcium metal

  • Reducing agent in the extraction of other metals such as uranium, zirconium, and thorium;
  • Deoxidizer, desulphurizing or decarbonizing for different Alloy S Iron reux and non-ferrous;
  • Used, sometimes in partnership with the Magnesium, to eliminate bismuth from the Lead (débismuthage);
  • Agent of alloy used in the production of alloys of the Aluminum, the Beryllium, the Copper, the Lead and the Magnesium.

Composed of calcium

  • Carbonate of calcium CaCO3, very widespread in nature, because they is component basic rocks Calcaire S; it is by calcination of limestone that one obtains the quicklime; to also see: Calcite, Aragonite
  • Oxide of calcium CAD (sharp lime) and calcium hydroxide Ca (OH) 2 (extinct lime)
  • Aluminate of calcium (Al2O3, 3CaO): one of the components of the Clinker, and used for the clothes industry of refractory mortars
  • Carbide of calcium CaC2 (commonly called Carbide; its Hydrolyze produces Acétylène)
  • Halogénure S of calcium:
  • Nitride of calcium Ca3N2
  • Peroxide of calcium CaO2
  • Phosphide of Ca3P2 calcium (its hydrolysis generates Phosphine PH3)
  • Sulfure of calcium CaS
  • Phosphate of calcium Ca3 (PO4) 2
  • Silico-Calcium (alloy calcium Silicium) used in iron and steel industry
  • Calcium hypochlorite Ca (Clo) 2
  • Alun sulfate doubles aluminum and of Potassium, hydrated; it is used in dyeing (to fix to them dyes), for the conservation of the skins, the joining of the paper pulp, the hardening of the Plâtre

Calcium in the food

Calcium is by far the most abundant Minéral in the body. It is mainly stored in the Os, of which it forms integral part. It contributes to the formation of the latter, like that of the Dent S, and with the maintenance of their health. The Calcium plays also a crucial role in the Coagulation of blood, the maintenance of the blood Pression and the contraction of the Muscle S (of which the heart).

Physiological importance

Calcium is component important of a healthy mode. As opposed to what one believes, in fact the dairy products represent the best source of calcium, because the proportion calcium/phosphorus is not good there. Milk contains too much phosphorus indeed, which can involve an insufficient calcification. The body needs magnesium, silicon, of vitamins has, C and D, of proteins and phosphorus for good to assimilate it. It intervenes in the formation of the Os and the Dent S; its deficit thus will affect them (Ostéoporose, problems of growth). Its excess causes the appearance of renal calculi. Moreover, it intervenes in the cellular exchanges and is, so vital. Its blood rate (Calcémie) is extremely controlled, to avoid fatal variations at the organization. The Hormone S implied in this regulation are the Parathormone and the Calcitonine, although the “hormonal” role of calcitonine is discussed since its increase does not involve modification on the metabolism phospho caclic. It would be righter to regard the PTH and the calcitriol as the two principal hormones of the calcic metabolism phospho. See also Metabolism of calcium. Calcium is also used to control the body pH, it is salted out bones when there is an acidification of the internal medium caused by a consumption of acidifying product (Proteins, Laits…) and low fuel consumption of plants which have a alkanisant effect.

The risk of Cancer of the colon seems decreased by a mode rich in calcium. The majority of the epidemiological studies indicate that people whose food contains the most calcium less frequently have a cancer colorectal. More than 25 scientific publications show that calcium decreases carcinogenesis colic in the rodents. Lastly, three controlled clinical trials show that the catch of a calcium carbonate supplement (1-2 g/j) decreases the recurrence of the polyps by 15 to 30% at volunteers.

History

The lime was already prepared by the Romans as of the first century, but it is only in 1808 that calcium was discovered. By learning that Jöns Jacob Berzelius and Magnus Martin Pontin had prepared a calcium amalgam by electrolysis of lime in mercury, Sir Humphry Davy was able to insulate impure metal.

Occurrence

Calcium is the fifth most abundant element in the earth's crust (it forms some more than 3%) and an essential component for the formation of the bones, the teeth and the shells. Calcium also plays a very important part in cellular Physiologie.

Industrial production

Calcium is produced by aluminothermy of lime, i.e. a reaction of Oxydo-réduction where the lime − the calcium oxide CAD − is reduced by the Aluminum in furnaces where the vacuum is established.

In a simplified way:

\ begin {matrix} & \ \ 2Al + 3CaO & \ overrightarrow {\ qquad} & Al_2O_3 + 3Ca \ \ \ end {matrix}

One introduces into the furnace of the pastilles formed starting from a mixture of aluminum lime and powder. The furnace is heated electrically or using a fossile fuel. The calcium formed during the reaction is released in the form of vapor, and one lays out (in the circuit of aspiration establishing the vacuum in the furnace) a condenser where it comes to settle. The residue of the reaction is calcium aluminate (combination of alumina and lime).

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