On the Spectrum of Argon

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Try again? Cited by. Back to tab navigation Download options Please wait Correction HTM 3K. Article type: Paper. DOI: Download Citation: J. Emission spectra of copper and argon in an argon glow discharge containing small quantities of hydrogen V.

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Hodoroaba, V. Argon is isolated from air by fractionation, most commonly by cryogenic fractional distillation , a process that also produces purified nitrogen , oxygen , neon , krypton and xenon. The main isotopes of argon found on Earth are 40 Ar Naturally occurring 40 K , with a half-life of 1.

These properties and ratios are used to determine the age of rocks by K—Ar dating. In the Earth's atmosphere, 39 Ar is made by cosmic ray activity, primarily by neutron capture of 40 Ar followed by two-neutron emission. In the subsurface environment, it is also produced through neutron capture by 39 K , followed by proton emission. It has a half-life of 35 days. Between locations in the Solar System , the isotopic composition of argon varies greatly. Where the major source of argon is the decay of 40 K in rocks, 40 Ar will be the dominant isotope, as it is on Earth.

Argon produced directly by stellar nucleosynthesis , is dominated by the alpha-process nuclide 36 Ar. Correspondingly, solar argon contains The atmospheres of Mars , Mercury and Titan the largest moon of Saturn contain argon, predominantly as 40 Ar , and its content may be as high as 1. The predominance of radiogenic 40 Ar is the reason the standard atomic weight of terrestrial argon is greater than that of the next element, potassium , a fact that was puzzling when argon was discovered.

Mendeleev positioned the elements on his periodic table in order of atomic weight, but the inertness of argon suggested a placement before the reactive alkali metal. Henry Moseley later solved this problem by showing that the periodic table is actually arranged in order of atomic number see History of the periodic table. Argon's complete octet of electrons indicates full s and p subshells. This full valence shell makes argon very stable and extremely resistant to bonding with other elements. Before , argon and the other noble gases were considered to be chemically inert and unable to form compounds; however, compounds of the heavier noble gases have since been synthesized.

The first argon compound with tungsten pentacarbonyl, W CO 5 Ar, was isolated in However it was not widely recognised at that time. This discovery caused the recognition that argon could form weakly bound compounds, even though it was not the first. It forms at pressures between 4. Argon is produced industrially by the fractional distillation of liquid air in a cryogenic air separation unit; a process that separates liquid nitrogen , which boils at About , tonnes of argon are produced worldwide every year. Because of this, it is used in potassium—argon dating to determine the age of rocks.

Other noble gases would be equally suitable for most of these applications, but argon is by far the cheapest.

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Argon is inexpensive, since it occurs naturally in air and is readily obtained as a byproduct of cryogenic air separation in the production of liquid oxygen and liquid nitrogen : the primary constituents of air are used on a large industrial scale. The other noble gases except helium are produced this way as well, but argon is the most plentiful by far. The bulk of argon applications arise simply because it is inert and relatively cheap. Argon is used in some high-temperature industrial processes where ordinarily non-reactive substances become reactive.

For example, an argon atmosphere is used in graphite electric furnaces to prevent the graphite from burning. For some of these processes, the presence of nitrogen or oxygen gases might cause defects within the material. Argon is used in some types of arc welding such as gas metal arc welding and gas tungsten arc welding , as well as in the processing of titanium and other reactive elements.

An argon atmosphere is also used for growing crystals of silicon and germanium. Argon is used in the poultry industry to asphyxiate birds, either for mass culling following disease outbreaks, or as a means of slaughter more humane than the electric bath. Argon is denser than air and displaces oxygen close to the ground during gassing. Argon is sometimes used for extinguishing fires where valuable equipment may be damaged by water or foam. Liquid argon is used as the target for neutrino experiments and direct dark matter searches. The interaction between the hypothetical WIMPs and an argon nucleus produces scintillation light that is detected by photomultiplier tubes.

Two-phase detectors containing argon gas are used to detect the ionized electrons produced during the WIMP—nucleus scattering. Compared to xenon , argon is cheaper and has a distinct scintillation time profile, which allows the separation of electronic recoils from nuclear recoils. On the other hand, its intrinsic beta-ray background is larger due to 39 Ar contamination, unless one uses argon from underground sources, which has much less 39 Ar contamination. The 39 Ar activity in the atmosphere is maintained by cosmogenic production through the knockout reaction 40 Ar n,2n 39 Ar and similar reactions.

As a result, the underground Ar, shielded by rock and water, has much less 39 Ar contamination.

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Neutrino experiments include ICARUS and MicroBooNE , both of which use high-purity liquid argon in a time projection chamber for fine grained three-dimensional imaging of neutrino interactions. Argon is used to displace oxygen- and moisture-containing air in packaging material to extend the shelf-lives of the contents argon has the European food additive code E Aerial oxidation, hydrolysis, and other chemical reactions that degrade the products are retarded or prevented entirely.

High-purity chemicals and pharmaceuticals are sometimes packed and sealed in argon. In winemaking , argon is used in a variety of activities to provide a barrier against oxygen at the liquid surface, which can spoil wine by fueling both microbial metabolism as with acetic acid bacteria and standard redox chemistry. Argon is sometimes used as the propellant in aerosol cans for such products as varnish , polyurethane , and paint, and to displace air when preparing a container for storage after opening. Since , the American National Archives stores important national documents such as the Declaration of Independence and the Constitution within argon-filled cases to inhibit their degradation.

Argon is preferable to the helium that had been used in the preceding five decades, because helium gas escapes through the intermolecular pores in most containers and must be regularly replaced.

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Argon may be used as the inert gas within Schlenk lines and gloveboxes. Argon is preferred to less expensive nitrogen in cases where nitrogen may react with the reagents or apparatus. Argon may be used as the carrier gas in gas chromatography and in electrospray ionization mass spectrometry ; it is the gas of choice for the plasma used in ICP spectroscopy. Argon is preferred for the sputter coating of specimens for scanning electron microscopy. Argon gas is also commonly used for sputter deposition of thin films as in microelectronics and for wafer cleaning in microfabrication.

Cryosurgery procedures such as cryoablation use liquid argon to destroy tissue such as cancer cells. It is used in a procedure called "argon-enhanced coagulation", a form of argon plasma beam electrosurgery. The procedure carries a risk of producing gas embolism and has resulted in the death of at least one patient. Blue argon lasers are used in surgery to weld arteries, destroy tumors, and correct eye defects. Argon has also been used experimentally to replace nitrogen in the breathing or decompression mix known as Argox , to speed the elimination of dissolved nitrogen from the blood.

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Incandescent lights are filled with argon, to preserve the filaments at high temperature from oxidation. It is used for the specific way it ionizes and emits light, such as in plasma globes and calorimetry in experimental particle physics. Argon is also used for blue and green argon-ion lasers. Argon is used for thermal insulation in energy-efficient windows.

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Compressed argon gas is allowed to expand, to cool the seeker heads of some versions of the AIM-9 Sidewinder missile and other missiles that use cooled thermal seeker heads. The gas is stored at high pressure. Argon, with a half-life of years, has been used for a number of applications, primarily ice core and ground water dating. Also, potassium—argon dating and related argon-argon dating is used to date sedimentary , metamorphic , and igneous rocks. Argon has been used by athletes as a doping agent to simulate hypoxic conditions.

In , the World Anti-Doping Agency WADA added argon and xenon to the list of prohibited substances and methods, although at this time there is no reliable test for abuse.

It is difficult to detect because it is colorless, odorless, and tasteless. A incident, in which a man was asphyxiated after entering an argon-filled section of oil pipe under construction in Alaska , highlights the dangers of argon tank leakage in confined spaces and emphasizes the need for proper use, storage and handling.

From Wikipedia, the free encyclopedia. This article is about the chemical element. For other uses, see Argon disambiguation. Chemical element with atomic number Main article: Isotopes of argon. Main article: Argon compounds.

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See also: shielding gas. See also: Air-free technique. Lein, Daniel A. Morgan Kirk Othmer Encyclopedia of Chemical Technology. See Group periodic table.

Retrieved 14 October Argon's not so noble after all — researchers make argon fluorohydride". Science News. Journal of Physics: Conference Series. Bibcode : JPhCS.. Journal of Chemical Physics.