(Chemical symbol: Ar) A colorless, tasteless, odorless, nonflammable gaseous element; atomic number: 18; atomic weight: 39.94; specific gravity (air = 1) 1.378; critical temperature: -122.5″C (-188.5″F); critical pressure: 4865 kPa (705.6 psia).
Argon was discovered in 1895 by Lord Rayleigh and Sir William Ramsey. About 0.8% of the earth’s atmosphere is made up of argon, and it is also found in volcanic gases. Argon is an inert gas; inert gases do not react with other elements. It is used as a shielding gas in certain forms of arc welding.
Argon is commercially available in purity exceeding 99.996% in the gaseous and liquid form. One gallon of liquid argon will produce 113.2 cu ft at 70°F. The boiling point of argon is -185.9″C (-302.6″F).