Argon (Ar) is a colourless, odourless, non-reactive, inert gas. In high concentrations, it has an asphyxiating effect. As argon is an atmospheric gas (0.93% vol.), it is generally sourced by separating air. A crude argon stream containing up to 5% oxygen is removed from the main air separation column and purified to produce the commercial purity grade required. Argon can also be recovered from the exhaust streams of certain ammonia plants.
Argon has many different applications in many industries. The most common one is as a shielding gas for arc welding – either in pure form or as part of various mixtures. It is one of the main gases used in filling mixtures for incandescent (filament) lamps, phosphorescent tubes and thyratron radio tubes.
It is also used as a carrier gas in chromatography, sputtering, plasma etching and ion implantations. It provides a blanket atmosphere in crystal growth, viniculture and pharmaceutical packaging. For excimer lasers, argon is blended with fluorine and helium. As an insulation gas, argon is a popular way of improving thermal insulation in multi-pane windows.
It has many protective applications in iron, steel and heat treatment industries – particularly in the case of metals susceptible to nitriding when treated with a nitrogen-based atmosphere.
Less common applications include cryosurgery, refrigeration, decarburising of stainless steel, airbag inflation, fire extinguishing, spectroscopy, spectrometry and purging or balancing in laboratories.