n. Symbol Ar
A colorless, odorless, inert gaseous element constituting approximately one percent of the earth's atmosphere, from which it is commercially obtained by fractionation for use in electric light bulbs, fluorescent tubes, and radio vacuum tubes and as an inert gas shield in arc welding. Atomic number 18; atomic weight 39.948; melting point -189.36°C; boiling point -185.85°C. See Periodic Table.
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