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Boron is a metalloid chemical element with symbol B and atomic number 5. Produced entirely by cosmic ray spallation and supernovae and not by stellar nucleosynthesis, it is a low-abundance element in both the Solar system and the Earth's crust.〔(【引用サイトリンク】Q & A: Where does the element Boron come from? )〕 Boron is concentrated on Earth by the water-solubility of its more common naturally occurring compounds, the borate minerals. These are mined industrially as evaporites, such as borax and kernite. The largest proven boron deposits are in Turkey, which is also the largest producer of boron minerals. Chemically uncombined boron, which is found in small amounts in meteoroids, but is not found naturally on Earth. Industrially, very pure boron is produced with difficulty, as boron tends to form refractory materials containing small amounts of carbon or other elements. Several allotropes of boron exist: amorphous boron is a brown powder, and crystalline boron is black, extremely hard (about 9.5 on the Mohs scale), and a poor conductor at room temperature. The primary use of elemental boron is to make boron filaments, which are used in a similar way to carbon fibers in some high-strength materials. Almost all boron use is as chemical compounds. About half of global consumption of boron compounds is as an additive in glass fibers of boron-containing fiberglass used for insulation or structural materials. The next leading use is in polymers and ceramics, that play specialized roles as high-strength lightweight structural and refractory materials. Borosilicate glass glassware is desired for its greater strength and thermal shock resistance than ordinary soda lime glass. Boron compounds are also used as fertilizers in agriculture, and in sodium perborate bleaches. In small-volume uses, boron is a dopant in semiconductors, and boron-containing reagents are used as intermediates in the synthesis of organic fine chemicals. A few boron-containing organic pharmaceuticals are used, or are in study. Natural boron is composed of two stable isotopes, one of which (boron-10) has a number of uses as a neutron-capturing agent. In biology, borates have low toxicity in mammals (similar to table salt), but are more toxic to arthropods and are used as insecticides. Boric acid is mildly antimicrobial, and a natural boron-containing organic antibiotic is known. Boron is essential to life. Small amounts of boron compounds play a strengthening role in the cell walls of all plants, making boron a necessary plant nutrient. Boron is involved in the metabolism of calcium in both plants and animals. It is considered an essential nutrient for humans, and lack of boron is implicated in osteoporosis in humans. ==History== The word ''boron'' was coined from ''borax'', the mineral from which it was isolated, by analogy with ''carbon'', which it resembles chemically. For the etymology of ''borax'', see that article. Borax, its mineral form then known as tincal, glazes were used in China from AD 300, and some crude borax reached the West, where the Persian alchemist Jābir ibn Hayyān seemed to mention it in AD 700. Marco Polo brought some glazes back to Italy in the 13th century. Agricola, around 1600, reports the use of borax as a flux in metallurgy. In 1777, boric acid was recognized in the hot springs (soffioni) near Florence, Italy, and became known as ''sal sedativum'', with mainly medical uses. The rare mineral is called sassolite, which is found at Sasso, Italy. Sasso was the main source of European borax from 1827 to 1872, at which date American sources replaced it. Boron compounds were relatively rarely used chemicals until the late 1800s when Francis Marion Smith's Pacific Coast Borax Company first popularized these compounds and made them in volume and hence cheap.〔Hildebrand, G. H. (1982) "Borax Pioneer: Francis Marion Smith." San Diego: Howell-North Books. p. 267 ISBN 0-8310-7148-6〕 Boron was not recognized as an element until it was isolated by Sir Humphry Davy〔 and by Joseph Louis Gay-Lussac and Louis Jacques Thénard.〔 In 1808 Davy observed that electric current sent through a solution of borates produced a brown precipitate on one of the electrodes. In his subsequent experiments, he used potassium to reduce boric acid instead of electrolysis. He produced enough boron to confirm a new element and named the element ''boracium''.〔 Gay-Lussac and Thénard used iron to reduce boric acid at high temperatures. By oxidizing boron with air, they showed that boric acid is an oxidation product of boron.〔 Jöns Jakob Berzelius identified boron as an element in 1824.〔Berzelius produced boron by reducing a borofluoride salt; specifically, by heating potassium borofluoride with potassium metal. See: Berzelius, J. (1824) ("Undersökning af flusspatssyran och dess märkvärdigaste föreningar" ) (Part 2) (Investigation of hydrofluoric acid and of its most noteworthy compounds), ''Kongliga Vetenskaps-Academiens Handlingar'' (Proceedings of the Royal Science Academy), vol. 12, pp. 46–98; see especially pp. 88ff. Reprinted in German as: Berzelius, J. J. (1824) ("Untersuchungen über die Flußspathsäure und deren merkwürdigste Verbindungen" ), Poggendorff's ''Annalen der Physik und Chemie'', vol. 78, pages 113–150.〕 Pure boron was arguably first produced by the American chemist Ezekiel Weintraub in 1909.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「boron」の詳細全文を読む スポンサード リンク
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