Pure boron exists in at least four crystalline modifications or allotropes. It is not yet clear what the precise role of boron in plant life is, but most researchers agree that the element is in some way essential for the normal growth and functioning of apical meristems, the growing tips of plant shoots. Gigantism of several species of plants growing in soil naturally abundant in boron has been reported. In excess quantities, however, borates act as unselective herbicides. Boron deficiency can be alleviated by the application of soluble borates to the soil. Typical effects of long-term boron deficiency are stunted, misshapen growth vegetable “brown heart” and sugar beet “dry rot” are among the disorders due to boron deficiency. In the form of boric acid or borates, traces of boron are necessary for growth of many land plants and thus are indirectly essential for animal life. Get a Britannica Premium subscription and gain access to exclusive content. In the semiconductor industry, small, carefully controlled amounts of boron are added as a doping agent to silicon and germanium to modify electrical conductivity. Boron is also used in the nonferrous-metals industry, generally as a deoxidizer, in copper-base alloys and high-conductance copper as a degasifier, and in aluminum castings to refine the grain. Added as the ironalloyferroboron, it is present in many steels, usually in the range 0.001 to 0.005 percent. Limited quantities of elemental boron are widely used to increase hardness in steel. Pure crystalline boron may be prepared with difficulty by reduction of its bromide or chloride (BBr 3, BCl 3) with hydrogen on an electrically heated tantalum filament. The impure amorphous product, a brownish black powder, was the only form of boron known for more than a century. Sassolite-natural boric acid-occurs especially in Italy.īoron was first isolated (1808) by French chemists Joseph-Louis Gay-Lussac and Louis-Jacques Thenard and independently by British chemist Sir Humphry Davy by heating boron oxide (B 2O 3) with potassium metal. Boron occurs combined as borax, kernite, and tincalconite (hydrated sodium borates), the major commercial boron minerals, especially concentrated in the arid regions of California, and as widely dispersed minerals such as colemanite, ulexite, and tourmaline.
It constitutes about 0.001 percent by weight of Earth’s crust. It is hard enough (9.3 on Mohs scale) to scratch some abrasives, such as carborundum, but too brittle for use in tools. Pure crystalline boron is a black, lustrous semiconductor i.e., it conducts electricity like a metal at high temperatures and is almost an insulator at low temperatures. Properties, occurrence, and uses Boron Element On Periodic Table How well do you know their symbols? In this quiz you’ll be shown all 118 chemical symbols, and you’ll need to choose the name of the chemical element that each one represents. The periodic table is made up of 118 elements.
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