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An inert, noble gas element. Helium is a colorless, odorless gas that is much lighter than air. In 1868, the spectrum for helium was identified in the sun's corona during an eclipse by Lockyer and Frankland. Helium was isolated in 1890 by Hillebrand and identified by Ramsay in 1895 in the mineral cleveite. Helium has been used in dirigibles and balloons for elevation and is preferred over hydrogen because it is noncombustible. It is also used for cryogenics, leak detection, geological dating, luminous signs, lasers, and as an oxygen diluent in deep sea diving tanks. Although helium is naturally produced by the disintegration of radioactive element, it is anticipated that helium reserves will be depleted by the end of the 21st century.

Synonyms and Related Terms

He; hélium (Fr.); elio (It.); Hélio (Port.); helio (Esp.)


  • Noncombustible.
  • Asphyxiant.
  • Airgas: SDS

Physical and Chemical Properties

Slightly soluble in water. Insoluble in ethanol.

Composition He (atomic no. 2)
CAS 7440-59-7
Melting Point -272.2 C
Molecular Weight atomic wt = 4.00260
Boiling Point -268.9 C

Resources and Citations

  • Van Nostrand's Scientific Encyclopedia, Douglas M. Considine (ed.), Van Nostrand Reinhold, New York, 1976
  • Richard S. Lewis, Hawley's Condensed Chemical Dictionary, Van Nostrand Reinhold, New York, 10th ed., 1993
  • Random House, Webster's Encyclopedic Unabridged Dictionary of the English Language, Grammercy Book, New York, 1997
  • The Merck Index, Martha Windholz (ed.), Merck Research Labs, Rahway NJ, 10th edition, 1983 Comment: entry #4660
  • The American Heritage Dictionary or Encarta, via Microsoft Bookshelf 98, Microsoft Corp., 1998
  • G.S.Brady, Materials Handbook, McGraw-Hill Book Co., New York, 1971 Comment: p. 393

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