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A nonmetallic element that occurs in the earth's crust at concentrations of 0.001%. Boron is primarily mined as Borax in India, Russia, Persia and California. Boron was first separated as an element by J.L. Gay-Lussac and L.J. Thenard in 1808. It generally occurs as an amorphous brown powder, but it also forms black crystals that are nearly as hard as diamonds. Boron is used for fibers and filaments in composites and ceramics. It is also used in semiconductors, oxygen scavengers, rocket propellant, and brazing alloys. Trace amounts of boron (0.001-0.005%) are added to steel for increased hardness.

Synonyms and Related Terms

B; Boor (Ned.); bore (Fr.); Bor (Deut., Sven.); boro (It., Port., Esp.)


Dust ignites spontaneously in air. Fire and explosion hazard.

Hummel Croton: SDS

Physical and Chemical Properties

  • Flame color is green.
  • Soluble in concentrated acids. Insoluble in water, ethanol, ether.
Composition B (atomic no. 5)
Mohs Hardness 9.3 (crystalline)
Melting Point 2200 C
Density 2.45 g/ml
Molecular Weight atomic wt = 10.82
Boiling Point 2550 C

Resources and Citations

  • Chemical & Engineering News, American Chemical Society, Washington DC, 81 (36) , Sept. 8, 2003 Comment: E.J.Corey, p. 40
  • Richard S. Lewis, Hawley's Condensed Chemical Dictionary, Van Nostrand Reinhold, New York, 10th ed., 1993
  • Van Nostrand's Scientific Encyclopedia, Douglas M. Considine (ed.), Van Nostrand Reinhold, New York, 1976
  • The Merck Index, Martha Windholz (ed.), Merck Research Labs, Rahway NJ, 10th edition, 1983 Comment: entry 1373
  • G.S.Brady, Materials Handbook, McGraw-Hill Book Co., New York, 1971 Comment: p. 110
  • Random House, Webster's Encyclopedic Unabridged Dictionary of the English Language, Grammercy Book, New York, 1997
  • The American Heritage Dictionary or Encarta, via Microsoft Bookshelf 98, Microsoft Corp., 1998