MICRONUTRIENT ROLES IN PHYSIOLOGY AND HEALTH
Location: Grand Forks Human Nutrition Research Center
Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: May 1, 2005
Publication Date: January 1, 2006
Citation: Nielsen, F.H. 2006. Boron. In: Klasing, K.C., editor. Mineral Tolerance of Animals. 2nd Revised Edition. Washington DC; National Academies Press. p. 60-67.
Elemental boron (B) is a relatively inert metalloid that exists as either black monoclinic crytsals or yellow-brown amorphous powder when impure at room temperature. However, boron as an element does not occur in nature; it is always found bound to oxygen or in the borate form. The most common commercial compounds of boron are anhydrous, pentahydrate and decahydrate (tincal) forms of disodium tetraborate (borax, Na2B407), colemanite (2CaO'3B2O3'5H2O), ulexite (Na2O'2CaO'5B2O3'16H2O), boric acid (H3BO3), and monohydrate and tetrahydrate forms of sodium perborate (NaBO3) (Woods, 1994). The borate industry began in 1865 with the mining of borate pandermite (priceite, 4CaO'5B2O3'7H2O) in Turkey. Shortly thereafter, several borate deposits were found in California and Nevada including ulexite and colemanite in Death Valley. Subsequently, tincal, colemanite and kernite (Na2O'2B2O3'4H2O) were found and mined in the Mojave Desert (Woods, 1994). In addition to Turkey and the United States, other countries producing borates are Peru, Chile, Russia, and China. Sodium perborates are hydrolytically unstable compounds containing boron-oxygen-oxygen bonds; they are used as bleaches in detergents. The end uses of boric acid and borates are diverse and include glass, enamel, and synthetic gems manufacturing, wood and leather perservatives, flame retardants, cosmetics, medical products, detergents, fertilizers, and neutron absorbers for the nuclear industry. Boron halides and hydrides are used as catalysts and in jet and rocket fuels. Elemental boron and its carbides and nitrides are used in high-temperature abrasives and in steelmaking (Larsen, 1988).