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An inert, colorless, odorless, gaseous element. Argon has an abundance of 0.935% in the earth's atmosphere. It was discovered in 1894 by Lord Rayleigh and Sir William Ramsay. Argon is inert but will form compounds with highly electronegative elements such as Oxygen and Fluorine. It is used as a filler in incandescent lightbulbs and neon-type bulbs where it produces a purple fluorescence. Argon is also used in some lasers.

Synonyms and Related Terms

Ar; argo (It.); argônio (Port. Brazil); árgon (Port.); argón (Esp.); Argon (Ces., Dan., Deut., Fr., It., Ned., Pol., Slov., Sven.)


  • Can act as an asphyxiant by displacing air.
  • Airgas: SDS

Physical and Chemical Properties

Emits purple light when an electric current is passed through.

Composition Ar (atomic no. 18)
CAS 7440-37-1
Melting Point -189.3 C
Molecular Weight atomic wt = 39.948
Boiling Point -185.7 C

Resources and Citations

  • Van Nostrand's Scientific Encyclopedia, Douglas M. Considine (ed.), Van Nostrand Reinhold, New York, 1976
  • Chemical & Engineering News, American Chemical Society, Washington DC, 81 (36) , Sept. 8, 2003
  • Richard S. Lewis, Hawley's Condensed Chemical Dictionary, Van Nostrand Reinhold, New York, 10th ed., 1993
  • The Merck Index, Martha Windholz (ed.), Merck Research Labs, Rahway NJ, 10th edition, 1983
  • G.S.Brady, Materials Handbook, McGraw-Hill Book Co., New York, 1971
  • 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