Extensive borax deposits are also found in Turkey. High purity boron is prepared by the vapour phase reduction of boron trichloride or tribromide with hydrogen on electrically heated filaments. The impure, or amorphous, boron can be prepared by heating the trioxide with magnesium powder. Uses Amorphous boron is used in pyrotechnic flares to provide a distinctive green colour, and in rockets as an igniter. The most important compounds of boron are boric, or boracic acid, widely used as a mild antiseptic, and borax which serves as a cleansing flux in welding and as a water softener in washing powders.
Boron compounds are also extensively used in the manufacture of borosilicate glasses.
Other boron compounds show promise in treating arthritis. The isotope boron 10 is used as a control for nuclear reactors, as a shield for nuclear radiation, and in instruments used for detecting neutrons. Demand is increasing for boron filaments, a high-strength, lightweight material chiefly employed for advanced aerospace structures. Biological Role Elemental boron is not considered a poison, and indeed is essential to plants, but assimilation of its compounds has a cumulative toxic effect. General Information Elemental boron has an energy band gap of 1.50 to 1.56 eV, which is higher than that of either silicon or germanium.