Calcium Phosphate

The tribasic phosphoric acid forms three types of salts with calcium. It is calcium hydrogen phosphate CaHPO4, calcium dihydrophosphate Ca (H2PO4) 2 and orthophosphate or calcium phosphate, the formula of which is: Ca3 (PO4) 2. This salt is an inorganic substance, under standard conditions, is in the solid state, and in liquid passes (melts) at a temperature of more than 1200 C. The density is 2.81 g / cm3, the molar mass is 310.2 g / mol. Calcium phosphate is poorly soluble in water: at 20 C, its mass fraction does not exceed 0.0025%. Unlike most other compounds, its solubility level decreases with increasing temperature. Thus, in heating systems, this salt is capable of forming deposits.

Calcium phosphate is a white crystalline substance that is part of the minerals of apatite (it belongs to the class of phosphates containing up to 56% CaO and about 41% P2O5), phosphorite (a fibrous or dense apatite aggregate containing more than 18% P2O5) and hydroxylapatites (The main component of bone tissue in humans and animals). The origin of some deposits from excrement or corpses of animals is proved. Other deposits (for example, in the ancient seas) were formed as a result of the life activity of "phosphorobacteria". But in some places the deposits of this mineral are of purely mineral origin. All of them are widely distributed in nature and are used in the national economy.

Apatite serves as a raw material for the production of phosphorus, phosphorus fertilizers and phosphoric acid, and is also used in nonferrous and ferrous metallurgy, in the production of glass and ceramics. Natural minerals, phosphorites are rocks of various origins, but more often sedimentary, they are used for further enrichment and in the production of phosphate fertilizers. The reserves of phosphorites and apatites are of great importance for agriculture, as they are used not only for fertilizers, but also as a source of calcium for feeding birds or livestock: calcium phosphate feed is produced in accordance with GOST 23999-80.

Mineral of inorganic origin - apatite - finds application in more than twenty production processes. It is used in the production of abrasives, glass and ceramics, as well as for the production of phosphoric acid and free phosphorus. The process proceeds according to the scheme: 3SiO2 + Ca3 (PO4) 2 + 5C → 3CaSiO3 + 5CO + 2P. This substance is also in demand in the food industry: it is produced in the form of food additives Е341 according to GOST R 53945-2010, where, together with 1- and 2-substituted salts of orthophosphoric acid, calcium phosphate enters. The receipt of this product implies strict requirements to the raw materials. In the production of food additives use orthophosphoric acid grade A according to GOST 10678-76, calcium hydroxide according to GOST 9262-77 and chemically precipitated chalk according to GOST 8253-79.

The mineral containing calcium phosphate plays an important role in the human body. Hydroxylapatite can be represented by the formula 3Ca3 (PO4) 3 • Ca (OH) 2. It is the main component and building material of human bones. This mineral is a part of the tooth enamel in the form of fluorapatite. The daily requirement for phosphorus is large and lies in the range from 800 to 1500 mg. The metabolism of phosphorus compounds in the human body is the liver, and this process is regulated by hormones and vitamin D. Various diseases of bones and teeth develop with a deficiency in the body of phosphorus. Calcium phosphate comes with food, strengthens teeth and bones, and in combination with other minerals supports the work of the cardiovascular system, prevents the appearance of colon cancer, regulates the functions of the nerves, participates in the construction of collagen, helps reduce cholesterol. Phosphates are excreted with feces, and with urine, about 4 g of phosphoric acid salts are released daily.

The main sources of calcium phosphate for humans are cow's milk and dairy products, cereals, fortified juices, cheese, goat's milk, salmon, sardines and anchovies. Being poorly soluble in water, calcium phosphate is in a high concentration in milk, as it exists in the colloidal system in the form of micelles, consisting of a very small insoluble core, which is surrounded by solvent molecules and adsorbed ions. It is part of the casein milk, more precisely, calcium caseinate, which refers to phosphoproteins, since it contains a phosphate group. However, experts recommend avoiding excess calcium phosphate, especially in the form of fortified foods and supplements, if a person has one of the following diseases: parathyroid glands, kidney stones or during a permanent treatment, including tetracycline antibiotics.