Argon is a chemical element with symbol Ar and atomic number 18. It is in group 18 of the periodic table and is a noble gas. Argon is the third most common gas in the Earth's atmosphere, at 0.93% (9,300 ppm), making it approximately 23.8 times as abundant as next most common atmospheric gas, carbon dioxide (390 ppm), and more than 500 times as abundant as the next most common noble gas, neon (18 ppm). Nearly all of this argon is radiogenic argon-40 derived from the decay of potassium-40 in the Earth's crust.
Argon is colorless, odorless and tasteless. It is know as one of the "Nobel" gases since it does not react reality with other materials and forms no known chemical compounds. It is nonflammable, will not support combustion and is not life-supporting. The gas is heavier than air and is only slightly soluble in water. When liquid argon is vaporized and then heated it consumes a large amount of heat, making it an ideal coolant.
Argon is present in the atmosphere at a concentration of ~1%. Argon is recovered from air in an Air Separation Unit (ASU) where it is drawn off as a cryogenic liquid at about -308°F. Argon can then be distributed as a cryogenic liquid or as a gas in cylinders.
Manufature :-
Oxygen, nitrogen and argon are recovered from air using a cryogenic method developed by Carl von Linde more than 100 years ago. Particulates are removed from the incoming air, which is then repeatedly compressed and cooled. Water, hydrocarbons and carbon dioxide are then removed. With further processing, the air eventually becomes a liquid and the individual gases are separated by distillation. These plants are called air separation units, or Air Separation Units (ASU). Many of the world's ASUs have been built by Linde's engineering division.
Specification :-
- Argon 99.999%
- Oxygen <2vpm
- Moisture <1vpm
- Nitrogen <6vpm
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Features :-
- Refrigerated liquid gas
- Boiling point -186°C
- Non-flammable
- Heavier than air
- Inert at most temperatures and pressures
- Colourless and odourless
- Constitutes 0.93% of atmospheric air
Application and use :-
- Electronics : In the semiconductor industry, argon is used in a number of device fabrication steps but its largest volume use is as a protective atmosphere in the manufacture of single crystal silicon by a number of processes known as crystal pulling.
- Fabrication : Argon is used as a shielding gas for MIG and TIG Welding processes and plasma-cutting.Argon is used alone or mixed with other gases such as helium, carbon dioxide, oxygen, nitrogen or hydrogen.
- Lasers : Argon can be used for the assist gas for the laser cutting of titanium as well as laser welding in CO2, ND:YAG and Diode machines.
- Metals : The argon-oxygen decarburising (AOD) process is the most common method of refining stainless steel. Argon is used to prevent oxidation of molten metals and alloys and for degassing and desulphurisation of molten iron and steel.
- Spectrographic analysis : Arc-spark analysis uses argon in the process of measuring the characteristic wavelength of light generated by striking an arc onto the metallic sample being analysed.
- Window unit insulation/Double-glazing : Argon is used to fill the inter-space in double-glazed window units because of its low thermal conductivity relative to air or nitrogen.