Boron

BORON, Borum (chemical symbol B, atomic weight 10.82, with two isotopes), discovered in 1807 by Davy. Found in nature in the form of free boric acid - orthoacid - sassolite (Italy) and in the form of various of its salts (California, Turkey, Tibet, Uzbekistan, Chile and other places). In the USSR, the discovered deposits of boron derivatives are still very insignificant. Borax and boric acid are almost completely (a little less than 2,000 tons per year) obtained from foreign boron minerals and go to the needs of metalworking (610 tons), silicate (500 tons), textile industry and the State Medical Trade Industry. Pure boron is a greenish-brown powder; with traces of Al and C it is crystalline; in hardness, refractive index and other properties it resembles diamond; specific gravity about 2.5, melting point about 2,300°. With hydrogen it gives compounds B₂H₆, B₄H₁₀ and other gaseous, liquid and solid boranes, analogous to hydrocarbons. In compounds with O and halogens, boron is trivalent, according to its position (5th place, III group) in the periodic system of elements. Of compounds with O, derivatives of boric anhydride B₂O₃ - boric acid and borax deserve special attention. Boric acid, Acidum boricum, H₃BO₃ (Ph VII), in Tuscany is separated with water vapor from cracks in the mountains (fumaroles). In pure form it is usually obtained from borax, displacing it with acids (hydrochloric or nitric). The main supplier of boric acid is the U.S.A. (100-150 thousand tons). In pure form, boric acid appears as colorless, shiny flakes, silky and greasy to the touch, or a fine white powder, with an acidic taste, specific gravity 1.48. It dissolves with difficulty in cold water (1:25) and slowly, easily and quickly in hot water (1:3), alcohol (1:18), glycerin (1:4); it colors flame green and curcuma paper brown. With metals it forms, predominantly, monometallic salts of the type NaBO₂·H₂O, i.e., salts of metaboric acid HBO₂, which is easily formed in pure form from H₃BO₃ when heated to 100° and is called Ac. boricum fusum; upon further heating (to 160°) it passes into tetraboric acid - H₂B₄O₇, known in the form of sodium salt under the name borax, Natr. boricum (old name - Natr. biboricum), Borax (Ph VII); from water it crystallizes in the form of prismatic crystals of hydrate Na₂B₄O₇·10H₂O (at 60° the hydrate Na₂B₄O₇·5H₂O precipitates, used in jewelry), which upon calcination loses water and turns into calcined borax, Borax ustum; melted borax upon cooling turns into a glassy mass (borax pearl). The hydrate dissolves in 17 parts of cold water and ²/³ parts of boiling water (forming alkaline solutions), easily in glycerin. The antiseptic properties of boric acid are insignificant; its solution (1:100) only inhibits the growth of the bacillus of Siberian plague; for other microbes the same is achieved with a solution concentration of 1:500; on mold fungi boric acid acts even weaker; it hardly irritates tissues and does not coagulate proteins; its toxicity is weak, although there are cases of poisoning with boric acid even with fatal outcome, for example, when large doses of it are introduced into the stomach or when extensive and easily absorbable cavities are washed with it; poisoning causes gastroenteritis and collapse. - Boric acid is used in medicine for washing wounds and mucous membranes, as a non-irritating to tissues and painless antiseptic, in 1-4% aqueous solution; rarely - internally, 0.3-1.0 (with fermentation in the stomach and some infectious diseases); usually in the form of ointments, Ung. Acid. borici (1 part to 9 parts of fatty substance). When wounds were dusted with boric acid powder, poisoning phenomena were also observed due to resorption. It was previously used for preserving meat and other food products, but due to the toxicity of the preparation, this is everywhere prohibited by law, including in the USSR. - Borax is used for rinsing and wiping the oral mucosa, with stomatitis and thrush; internally - sometimes with uric acid diathesis in doses up to 10.0-15.0.