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For light bulbs.
(Gr. argos, inactive) Its presence in air was suspected by Cavendish in 1785,
discovered by Lord Rayleigh and Sir William Ramsay in 1894.
The gas is prepared by fractionation of liquid air because the atmosphere contains
0.94% argon. The atmosphere of Mars contains 1.6% of 40Ar and 5 p.p.m. of 36Ar.
Argon is two and one half times as soluble in water as nitrogen, having about the same
solubility as oxygen. Argon is colorless and odorless, both as a gas and liquid. Argon is
considered to be a very inert gas and is not known to form true chemical compounds, as do
krypton, xenon, and radon.
Naturally occurring argon is a mixture of three isotopes. Twelve other radioactive
isotopes are known to exist.
It is used in electric light bulbs and in fluorescent tubes at a pressure of about 400
Pa. and in filling photo tubes, glow tubes, etc. Argon is also used as an inert gas shield
for arc welding and cutting, as blanket for the production of titanium and other reactive
elements, and as a protective atmosphere for growing silicon and germanium crystals.
Sources: CRC Handbook of Chemistry
and Physics and the American Chemical Society.