BARIUM, Ba (from the Latin word "Baryum", from the Greek word "barys", which means "heavy" * EN: barium; DE: Barium; FR: barium; ES: bario; RU: барий) is the chemical element of the main sub-group of the 11-th group of the periodic system of elements by Mendeleev, the atomic number is 56, the atomic mass is 137.33. The natural barium consists of the mixture of the seven stable isotopes; there prevails the 138 Ba isotope (71.66%). Barium has been discovered during the 1774 by the Swedish chemist Carl Scheele in the form of the BaO compound. There has obtained the metallic barium for the first time the English chemist Humphry Davy during the 1808.

Barium is the ductile malleable metal of the silvery-white colour. Barium crystallizes according to the cubic volume-centered type of the lattice with the parameter a = 5.019 Ångström. The density is 3630 kilograms per cubic metre (at 20 degrees Celsius). The temperature of the melting point is 727 degrees Celsius, the temperature of the boiling point is approximately 1860 degrees Celsius. The specific heat of fusion is 8673.3 ± 335.2 kilojoules per kilogram, the specific heat capacity is 2.84 • 10^2 joules per kilogram-kelvin (from 0 to 100 degrees Celsius). The specific electrical resistance is 6 • 10^-7 ohm-metre, the thermal coefficient of the linear expansion is 1.9 • 10^-5 per degree (from 0 to 100 degrees Celsius).

According to its chemical properties, barium is similar to calcium and strontium, while exceeding them according to its chemical activity. It oxidizes rapidly within the air, forming the film, which is containing the oxide, peroxide, and nitride of barium. During the heating within the air, it easily ignites and burns. It decomposes water with the emission of hydrogen more energetically than calcium. The most characteristic oxidation state for barium is +2, though there are known the compounds, within which the oxidation state of barium is +1 (for example, the BaCl compound). During the heating, barium interacts with hydrogen and nitrogen, forming the hydrides and nitrides (the BaH2 and Ba3N2 compounds). They obtain within the arc furnace the carbide BaC2 and phosphide Ba3P2 compounds. Barium sulfide, BaS, forms itself during the heating of the barium sulfate to 1200 degrees Celsius within the reducing atmosphere. Barium directly reacts with halogens, forming the salts of the corresponding hydrohalic acids. Barium forms alloys with lead, nickel, tin, iron. During the interaction of barium with the diluted acids, there are forming the [BaSO4, Ba(NO3)2] salts. Halides, nitrate, chloride, and certain other compounds of barium are toxic.

Barium is fairly common element; the content of it within the Earth's crust amounts to 5 • 10^-2%. The bulk mass of barium is located in the dispersed state within the erupted and sedimentary rocks. Of the sedimentary rocks, there are most beneficiated with barium the clays and argillaceous shales, of the erupted rocks, the acidic and alkaline ones. The main concentrates of barium within the erupted rocks are the potassic feldspars and micas, within which the accumulation of barium is caused by the K+ - Ba+ isomorphism. The important geochemical peculiarity of barium is the tendency to concentrate into the post-magmatic phase. Barium is transferred in the form of the soluble compounds. There are known 10 its own minerals of barium. The main mineral of barium is the barite. There are less common the witherite, celsian - Ba[Al2Si2O3], gialofan - K2Ba[Al2Si4O12], and others.

About the major genetic types of the deposits of the natural raw materials of barium, and about its beneficiation, see within the "Barite ores" article.

They obtain the metallic barium by the thermal reduction of the barium oxide by the powder of aluminium at the temperature of 1100-1200 degrees Celsius within the vacuum. They use barium within the alloys, namely, with lead (printing and anti-friction alloys), with aluminium and magnesium (gas absorbers within the vacuum systems). They use widely its artificial radioactive isotopes.

They add barium and its compounds to the materials, which are purposed for the protection against the radioactive and X-ray radiation. There are widely used the compounds of barium: oxide, peroxide, and hydroxide (for the obtainment of the hydrogen peroxide), nitride (within the pyrotechnics), sulfate (as the contrast substance during the X-ray and other researches), chromate and manganate (during the manufacturing of paints), titanate (one of the most important ferroelectrics), sulfide (within the leather industry), and so on.