Argon is a
chemical element
A chemical element is a species of atoms that have a given number of protons in their nuclei, including the pure substance consisting only of that species. Unlike chemical compounds, chemical elements cannot be broken down into simpler sub ...
with the
symbol Ar and
atomic number 18. It is in group 18 of the
periodic table and is a
noble gas
The noble gases (historically also the inert gases; sometimes referred to as aerogens) make up a class of chemical elements with similar properties; under standard conditions, they are all odorless, colorless, monatomic gases with very low ch ...
. Argon is the third-most abundant
gas
Gas is one of the four fundamental states of matter (the others being solid, liquid, and plasma).
A pure gas may be made up of individual atoms (e.g. a noble gas like neon), elemental molecules made from one type of atom (e.g. oxygen), or ...
in
Earth's atmosphere, at 0.934% (9340
ppmv). It is more than twice as abundant as
water vapor (which averages about 4000 ppmv, but varies greatly), 23 times as abundant as
carbon dioxide (400 ppmv), and more than 500 times as abundant as
neon (18 ppmv). Argon is the most abundant noble gas in
Earth's crust, comprising 0.00015% of the crust.
Nearly all of the argon in Earth's atmosphere is
radiogenic argon-40, derived from the
decay of
potassium-40
Potassium-40 (40K) is a radioactive isotope of potassium which has a long half-life of 1.25 billion years. It makes up about 0.012% (120 ppm) of the total amount of potassium found in nature.
Potassium-40 undergoes three types of radioactive d ...
in Earth's crust. In the universe,
argon-36 is by far the most common argon
isotope
Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers (mass numb ...
, as it is the most easily produced by stellar
nucleosynthesis
Nucleosynthesis is the process that creates new atomic nuclei from pre-existing nucleons (protons and neutrons) and nuclei. According to current theories, the first nuclei were formed a few minutes after the Big Bang, through nuclear reactions in ...
in
supernovas.
The name "argon" is derived from the
Greek
Greek may refer to:
Greece
Anything of, from, or related to Greece, a country in Southern Europe:
*Greeks, an ethnic group.
*Greek language, a branch of the Indo-European language family.
**Proto-Greek language, the assumed last common ancestor ...
word , neuter singular form of meaning 'lazy' or 'inactive', as a reference to the fact that the element undergoes almost no chemical reactions. The complete
octet (eight electrons) in the outer atomic shell makes argon stable and resistant to bonding with other elements. Its
triple point temperature of 83.8058
K is a defining fixed point in the
International Temperature Scale of 1990.
Argon is extracted industrially by the
fractional distillation of
liquid air. Argon is mostly used as an
inert shielding gas in welding and other high-temperature industrial processes where ordinarily unreactive substances become reactive; for example, an argon atmosphere is used in
graphite electric furnaces to prevent the graphite from burning. Argon is also used in
incandescent,
fluorescent lighting
A fluorescent lamp, or fluorescent tube, is a low-pressure mercury-vapor gas-discharge lamp that uses fluorescence to produce visible light. An electric current in the gas excites mercury vapor, which produces short-wave ultraviolet ligh ...
, and other gas-discharge tubes. Argon makes a distinctive
blue-green gas laser. Argon is also used in fluorescent glow starters.
Characteristics
Argon has approximately the same
solubility in water as
oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as ...
and is 2.5 times more soluble in water than
nitrogen
Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...
. Argon is colorless, odorless, nonflammable and nontoxic as a solid, liquid or gas. Argon is chemically
inert under most conditions and forms no confirmed stable compounds at room temperature.
Although argon is a
noble gas
The noble gases (historically also the inert gases; sometimes referred to as aerogens) make up a class of chemical elements with similar properties; under standard conditions, they are all odorless, colorless, monatomic gases with very low ch ...
, it can form some compounds under various extreme conditions.
Argon fluorohydride
Argon fluorohydride (systematically named fluoridohydridoargon) or argon hydrofluoride is an inorganic compound with the chemical formula HArF (also written ArHF). It is a compound of the chemical element argon.
Discovery
The discovery of thi ...
(HArF), a compound of argon with
fluorine and
hydrogen
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic ...
that is stable below , has been demonstrated.
[
] Although the neutral ground-state chemical compounds of argon are presently limited to HArF, argon can form
clathrates with water when atoms of argon are trapped in a lattice of water molecules.
Ions
An ion () is an atom or molecule with a net electrical charge.
The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conven ...
, such as , and
excited-state complexes, such as ArF, have been demonstrated. Theoretical calculation predicts several more
argon compounds
Argon compounds, the chemical compounds that contain the element argon, are rarely encountered due to the inertness of the argon atom. However, compounds of argon have been detected in inert gas matrix isolation, cold gases, and plasmas, and molec ...
that should be stable but have not yet been synthesized.
History
''Argon'' (
Greek
Greek may refer to:
Greece
Anything of, from, or related to Greece, a country in Southern Europe:
*Greeks, an ethnic group.
*Greek language, a branch of the Indo-European language family.
**Proto-Greek language, the assumed last common ancestor ...
, neuter singular form of meaning "lazy" or "inactive") is named in reference to its chemical inactivity. This chemical property of this first
noble gas
The noble gases (historically also the inert gases; sometimes referred to as aerogens) make up a class of chemical elements with similar properties; under standard conditions, they are all odorless, colorless, monatomic gases with very low ch ...
to be discovered impressed the namers.
[
][
] An unreactive gas was suspected to be a component of air by
Henry Cavendish
Henry Cavendish ( ; 10 October 1731 – 24 February 1810) was an English natural philosopher and scientist who was an important experimental and theoretical chemist and physicist. He is noted for his discovery of hydrogen, which he termed "infl ...
in 1785.
Argon was first isolated from air in 1894 by
Lord Rayleigh
John William Strutt, 3rd Baron Rayleigh, (; 12 November 1842 – 30 June 1919) was an English mathematician and physicist who made extensive contributions to science. He spent all of his academic career at the University of Cambridge. Am ...
and Sir
William Ramsay
Sir William Ramsay (; 2 October 1852 – 23 July 1916) was a Scottish chemist who discovered the noble gases and received the Nobel Prize in Chemistry in 1904 "in recognition of his services in the discovery of the inert gaseous element ...
at
University College London
, mottoeng = Let all come who by merit deserve the most reward
, established =
, type = Public research university
, endowment = £143 million (2020)
, budget = ...
by removing
oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as ...
,
carbon dioxide, water, and
nitrogen
Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...
from a sample of clean air.
[
] They first accomplished this by replicating an experiment of
Henry Cavendish
Henry Cavendish ( ; 10 October 1731 – 24 February 1810) was an English natural philosopher and scientist who was an important experimental and theoretical chemist and physicist. He is noted for his discovery of hydrogen, which he termed "infl ...
's. They trapped a mixture of atmospheric air with additional oxygen in a test-tube (A) upside-down over a large quantity of dilute
alkali solution (B), which in Cavendish's original experiment was potassium hydroxide,
and conveyed a current through wires insulated by U-shaped glass tubes (CC) which sealed around the platinum wire electrodes, leaving the ends of the wires (DD) exposed to the gas and insulated from the alkali solution. The arc was powered by a battery of five
Grove cell
The Grove cell was an early electric primary cell named after its inventor, Welsh physical scientist William Robert Grove, and consisted of a zinc anode in dilute sulfuric acid and a platinum cathode in concentrated nitric acid, the two separated ...
s and a
Ruhmkorff coil of medium size. The alkali absorbed the oxides of nitrogen produced by the arc and also carbon dioxide. They operated the arc until no more reduction of volume of the gas could be seen for at least an hour or two and the spectral lines of nitrogen disappeared when the gas was examined. The remaining oxygen was reacted with alkaline pyrogallate to leave behind an apparently non-reactive gas which they called argon.
Before isolating the gas, they had determined that nitrogen produced from chemical compounds was 0.5% lighter than nitrogen from the atmosphere. The difference was slight, but it was important enough to attract their attention for many months. They concluded that there was another gas in the air mixed in with the nitrogen. Argon was also encountered in 1882 through independent research of H. F. Newall and W. N. Hartley. Each observed new lines in the
emission spectrum of air that did not match known elements.
Until 1957, the symbol for argon was "A", but now it is "Ar".
Occurrence
Argon constitutes 0.934% by volume and 1.288% by mass of
Earth's atmosphere. Air is the primary industrial source of purified argon products. Argon is isolated from air by fractionation, most commonly by
cryogenic fractional distillation, a process that also produces purified
nitrogen
Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...
,
oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as ...
,
neon,
krypton and
xenon. Earth's crust and seawater contain 1.2 ppm and 0.45 ppm of argon, respectively.
Isotopes
The main
isotope
Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers (mass numb ...
s of argon found on Earth are (99.6%), (0.34%), and (0.06%). Naturally occurring , with a
half-life of 1.25 years, decays to stable (11.2%) by
electron capture or
positron emission
Positron emission, beta plus decay, or β+ decay is a subtype of radioactive decay called beta decay, in which a proton inside a radionuclide nucleus is converted into a neutron while releasing a positron and an electron neutrino (). Positron ...
, and also to stable (88.8%) by
beta decay. These properties and ratios are used to determine the age of
rocks by
K–Ar dating
Potassium–argon dating, abbreviated K–Ar dating, is a radiometric dating method used in geochronology and archaeology. It is based on measurement of the product of the radioactive decay of an isotope of potassium (K) into argon (Ar). Potassium ...
.
[
]
In Earth's atmosphere, is made by
cosmic ray activity, primarily by neutron capture of followed by two-neutron emission. In the subsurface environment, it is also produced through
neutron capture by , followed by proton emission. is created from the
neutron capture by followed by an
alpha particle emission as a result of subsurface
nuclear explosions. It has a half-life of 35 days.
Between locations in the
Solar System
The Solar System Capitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar ...
, the isotopic composition of argon varies greatly. Where the major source of argon is the decay of
in rocks, will be the dominant isotope, as it is on Earth. Argon produced directly by
stellar nucleosynthesis is dominated by the
alpha-process nuclide . Correspondingly, solar argon contains 84.6% (according to
solar wind
The solar wind is a stream of charged particles released from the upper atmosphere of the Sun, called the corona. This plasma mostly consists of electrons, protons and alpha particles with kinetic energy between . The composition of the sol ...
measurements), and the ratio of the three isotopes
36Ar :
38Ar :
40Ar in the atmospheres of the outer planets is 8400 : 1600 : 1. This contrasts with the low abundance of
primordial in Earth's atmosphere, which is only 31.5 ppmv (= 9340 ppmv × 0.337%), comparable with that of neon (18.18 ppmv) on Earth and with interplanetary gasses, measured by
probes.
The atmospheres of
Mars
Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury. In the English language, Mars is named for the Roman god of war. Mars is a terrestrial planet with a thin at ...
,
Mercury and
Titan (the largest moon of
Saturn) contain argon, predominantly as , and its content may be as high as 1.93% (Mars).
The predominance of
radiogenic 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
Dmitri Ivanovich Mendeleev (sometimes transliterated as Mendeleyev or Mendeleef) ( ; russian: links=no, Дмитрий Иванович Менделеев, tr. , ; 8 February Old_Style_and_New_Style_dates">O.S._27_January.html" ;"title="O ...
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).
Compounds
Argon's complete octet of
electrons indicates full s and p subshells. This full
valence shell
In chemistry and physics, a valence electron is an electron in the outer shell associated with an atom, and that can participate in the formation of a chemical bond if the outer shell is not closed. In a single covalent bond, a shared pair forms ...
makes argon very stable and extremely resistant to bonding with other elements. Before 1962, 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)
5Ar, was isolated in 1975. However, it was not widely recognised at that time. In August 2000, another argon compound,
argon fluorohydride
Argon fluorohydride (systematically named fluoridohydridoargon) or argon hydrofluoride is an inorganic compound with the chemical formula HArF (also written ArHF). It is a compound of the chemical element argon.
Discovery
The discovery of thi ...
(HArF), was formed by researchers at the
University of Helsinki, by shining ultraviolet light onto frozen argon containing a small amount of
hydrogen fluoride with
caesium iodide
Caesium iodide or cesium iodide (chemical formula CsI) is the ionic compound of caesium and iodine. It is often used as the input phosphor of an X-ray image intensifier tube found in fluoroscopy equipment. Caesium iodide photocathodes are highly ...
. This discovery caused the recognition that argon could form weakly bound compounds, even though it was not the first.
It is stable up to 17 kelvins (−256 °C). The
metastable
In chemistry and physics, metastability denotes an intermediate energetic state within a dynamical system other than the system's state of least energy.
A ball resting in a hollow on a slope is a simple example of metastability. If the ball i ...
dication, which is valence-
isoelectronic
Isoelectronicity is a phenomenon observed when two or more molecules have the same structure (positions and connectivities among atoms) and the same electronic configurations, but differ by what specific elements are at certain locations in th ...
with
carbonyl fluoride
Carbonyl fluoride is a chemical compound with the formula COF2. It is a carbon oxohalide. This gas, like its analog phosgene, is colourless and highly toxic. The molecule is planar with ''C''2v symmetry, bond lengths of 1.174 Å (C=O) and 1.312 ...
and
phosgene, was observed in 2010.
Argon-36, in the form of argon hydride (
argonium) ions, has been detected in
interstellar medium associated with the
Crab Nebula supernova; this was the first
noble-gas molecule detected in
outer space.
Solid argon
hydride
In chemistry, a hydride is formally the anion of hydrogen( H−). The term is applied loosely. At one extreme, all compounds containing covalently bound H atoms are called hydrides: water (H2O) is a hydride of oxygen, ammonia is a hydride ...
(Ar(H
2)
2) has the same crystal structure as the MgZn
2 Laves phase. It forms at pressures between 4.3 and 220 GPa, though Raman measurements suggest that the H
2 molecules in Ar(H
2)
2 dissociate above 175 GPa.
Production
Industrial
Argon is extracted industrially by the
fractional distillation of
liquid air in a
cryogenic air separation unit; a process that separates
liquid nitrogen, which boils at 77.3 K, from argon, which boils at 87.3 K, and
liquid oxygen, which boils at 90.2 K. About 700,000
tonnes of argon are produced worldwide every year.
In radioactive decays
40Ar, the most abundant
isotope
Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers (mass numb ...
of argon, is produced by the decay of
40 K with a half-life of 1.25 years by
electron capture or
positron emission
Positron emission, beta plus decay, or β+ decay is a subtype of radioactive decay called beta decay, in which a proton inside a radionuclide nucleus is converted into a neutron while releasing a positron and an electron neutrino (). Positron ...
. Because of this, it is used in
potassium–argon dating to determine the age of rocks.
Applications
Argon has several desirable properties:
* Argon is a chemically
inert gas.
* Argon is the cheapest alternative when
nitrogen
Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...
is not sufficiently inert.
* Argon has low
thermal conductivity.
* Argon has electronic properties (ionization and/or the emission spectrum) desirable for some applications.
Other
noble gas
The noble gases (historically also the inert gases; sometimes referred to as aerogens) make up a class of chemical elements with similar properties; under standard conditions, they are all odorless, colorless, monatomic gases with very low ch ...
es would be equally suitable for most of these applications, but argon is by far the cheapest. 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.
Industrial processes
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
Arc welding is a welding process that is used to join metal to metal by using electricity to create enough heat to melt metal, and the melted metals, when cool, result in a binding of the metals. It is a type of welding that uses a welding powe ...
such as
gas metal arc welding
Gas metal arc welding (GMAW), sometimes referred to by its subtypes metal inert gas (MIG) and metal active gas (MAG) is a welding process in which an electric arc forms between a consumable MIG wire electrode and the workpiece metal(s), which hea ...
and
gas tungsten arc welding
Gas tungsten arc welding (GTAW), also known as tungsten inert gas (TIG) welding, is an arc welding process that uses a non-consumable tungsten electrode to produce the weld. The weld area and electrode are protected from oxidation or other atm ...
, 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
electric stunning
Stunning is the process of rendering animals immobile or unconscious, with or without killing the animal, when or immediately prior to slaughtering them for food.
Rationale
Within the European Union, most animals slaughtered for human consumpt ...
. Argon is denser than air and displaces oxygen close to the ground during
inert gas asphyxiation
Inert gas asphyxiation is a form of asphyxiation which results from breathing a physiologically inert gas in the absence of oxygen, or a low amount of oxygen, rather than atmospheric air (which is composed largely of nitrogen and oxygen). Examples ...
.
Its non-reactive nature makes it suitable in a food product, and since it replaces oxygen within the dead bird, argon also enhances shelf life.
Argon is sometimes used for
extinguishing fires where valuable equipment may be damaged by water or foam.
Scientific research
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. As with most other liquefied noble gases, argon has a high scintillation light yield (about 51 photons/keV), is transparent to its own scintillation light, and is relatively easy to purify. 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 contamination, unless one uses argon from underground sources, which has much less contamination. Most of the argon in Earth's atmosphere was produced by electron capture of long-lived ( + e
− → + ν) present in natural potassium within Earth. The activity in the atmosphere is maintained by cosmogenic production through the knockout reaction (n,2n) and similar reactions. The half-life of is only 269 years. As a result, the underground Ar, shielded by rock and water, has much less contamination. Dark-matter detectors currently operating with liquid argon include
DarkSide,
WArP,
ArDM,
microCLEAN and
DEAP
DEAP (Dark matter Experiment using Argon Pulse-shape discrimination) is a direct dark matter search experiment which uses liquid argon as a target material. DEAP utilizes background discrimination based on the characteristic scintillation pulse- ...
. Neutrino experiments include
ICARUS and
MicroBooNE
MicroBooNE is a liquid argon time projection chamber (LArTPC) at Fermilab in Batavia, Illinois. It is located in the Booster Neutrino Beam (BNB) beamline where neutrinos are produced by colliding protons from Fermilab's booster-accelerator on a b ...
, both of which use high-purity liquid argon in a
time projection chamber for fine grained three-dimensional imaging of neutrino interactions.
At Linköping University, Sweden, the inert gas is being utilized in a vacuum chamber in which plasma is introduced to ionize metallic films. This process results in a film usable for manufacturing computer processors. The new process would eliminate the need for chemical baths and use of expensive, dangerous and rare materials.
Preservative
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 E938). 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
Acetic acid bacteria (AAB) are a group of Gram-negative bacteria which oxidize sugars or ethanol and produce acetic acid during fermentation. The acetic acid bacteria consist of 10 genera in the family Acetobacteraceae. Several species of acetic ...
) and standard
redox chemistry.
Argon is sometimes used as the propellant in
aerosol cans.
Argon is also used as a preservative for such products as
varnish,
polyurethane
Polyurethane (; often abbreviated PUR and PU) refers to a class of polymers composed of organic units joined by carbamate (urethane) links. In contrast to other common polymers such as polyethylene and polystyrene, polyurethane is produced from ...
, and paint, by displacing air to prepare a container for storage.
Since 2002, the American
National Archives stores important national documents such as the
Declaration of Independence
A declaration of independence or declaration of statehood or proclamation of independence is an assertion by a polity in a defined territory that it is independent and constitutes a state. Such places are usually declared from part or all of th ...
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.
Laboratory equipment
Argon may be used as the
inert gas within
Schlenk lines and
glovebox
A glovebox (or glove box) is a sealed container that is designed to allow one to manipulate objects where a separate atmosphere is desired. Built into the sides of the glovebox are gloves arranged in such a way that the user can place their hand ...
es. 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.
Medical use
Cryosurgery
Cryosurgery is the use of extreme cold in surgery to destroy abnormal or diseased tissue; thus, it is the surgical application of cryoablation. The term comes from the Greek words cryo (κρύο) ("icy cold") and surgery (''cheirourgiki'' – χ� ...
procedures such as
cryoablation use liquid argon to destroy tissue such as
cancer
Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal b ...
cells. It is used in a procedure called "argon-enhanced coagulation", a form of argon
plasma beam electrosurgery
Electrosurgery is the application of a high-frequency (radio frequency) alternating polarity, electrical current to biological tissue as a means to cut, coagulate, desiccate, or fulgurate tissue.Hainer BL, "Fundamentals of electrosurgery", ''J ...
. The procedure carries a risk of producing
gas embolism
An air embolism, also known as a gas embolism, is a blood vessel blockage caused by one or more bubbles of air or other gas in the circulatory system. Air can be introduced into the circulation during surgical procedures, lung over-expansion ...
and has resulted in the death of at least one patient.
Blue
argon laser
An ion laser is a gas laser that uses an ionized gas as its lasing medium.
Like other gas lasers, ion lasers feature a sealed cavity containing the laser medium and mirrors forming a Fabry–Pérot resonator. Unlike helium–neon lasers, the ...
s 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.
Lighting
Incandescent light
An incandescent light bulb, incandescent lamp or incandescent light globe is an electric light with a wire filament heated until it glows. The filament is enclosed in a glass bulb with a vacuum or inert gas to protect the filament from oxidat ...
s 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 globe
A plasma globe or plasma lamp is a clear glass container filled with a mixture of various noble gases with a high-voltage electrode in the center of the container.
When voltage is applied, a plasma is formed within the container. Plasma filam ...
s and
calorimetry in experimental
particle physics.
Gas-discharge lamps filled with pure argon provide lilac/violet light; with argon and some mercury, blue light. Argon is also used for blue and green
argon-ion lasers.
Miscellaneous uses
Argon is used for
thermal insulation in
energy-efficient windows. Argon is also used in technical
scuba diving to inflate a
dry suit because it is inert and has low thermal conductivity.
Argon is used as a propellant in the development of the
Variable Specific Impulse Magnetoplasma Rocket (VASIMR). Compressed argon gas is allowed to expand, to cool the seeker heads of some versions of the
AIM-9 Sidewinder
The AIM-9 Sidewinder (where "AIM" stands for "Air Intercept Missile") is a short-range air-to-air missile which entered service with the US Navy in 1956 and subsequently was adopted by the US Air Force in 1964. Since then the Sidewinder has prove ...
missile and other missiles that use cooled thermal seeker heads. The gas is
stored at high pressure.
Argon-39, with a half-life of 269 years, has been used for a number of applications, primarily
ice core and
ground water
Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations. About 30 percent of all readily available freshwater in the world is groundwater. A unit of rock or an unconsolidate ...
dating. Also,
potassium–argon dating and related
argon-argon dating are used to date
sedimentary,
metamorphic
Metamorphic rocks arise from the transformation of existing rock to new types of rock in a process called metamorphism. The original rock (protolith) is subjected to temperatures greater than and, often, elevated pressure of or more, causi ...
, and
igneous rock
Igneous rock (derived from the Latin word ''ignis'' meaning fire), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rock is formed through the cooling and solidification of magma o ...
s.
Argon has been used by athletes as a doping agent to simulate
hypoxic conditions. In 2014, the
World Anti-Doping Agency
The World Anti-Doping Agency (WADA; french: Agence mondiale antidopage, AMA) is a foundation initiated by the International Olympic Committee based in Canada to promote, coordinate, and monitor the fight against drugs in sports. The agency's key ...
(WADA) added argon and
xenon to the list of prohibited substances and methods, although at this time there is no reliable test for abuse.
Safety
Although argon is non-toxic, it is 38% more
dense
Density (volumetric mass density or specific mass) is the substance's mass per unit of volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' can also be used. Mathematically ...
than air and therefore considered a dangerous
asphyxiant in closed areas. It is difficult to detect because it is colorless, odorless, and tasteless. A 1994 incident, in which a man was
asphyxia
Asphyxia or asphyxiation is a condition of deficient supply of oxygen to the body which arises from abnormal breathing. Asphyxia causes generalized hypoxia, which affects primarily the tissues and organs. There are many circumstances that ca ...
ted 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.
[
]
See also
*
Industrial gas
*
Oxygen–argon ratio, a ratio of two physically similar gases, which has importance in various sectors.
References
Further reading
*
* On triple point pressure at 69 kPa.
* On triple point pressure at 83.8058 K.
External links
Argonat ''
The Periodic Table of Videos
''Periodic Videos'' (also known as ''The Periodic Table of Videos'') is a video project and YouTube channel on chemistry. It consists of a series of videos about chemical elements and the periodic table, with additional videos on other topics i ...
'' (University of Nottingham)
USGS Periodic Table – Argon* Diving applications
{{Authority control
Chemical elements
E-number additives
Noble gases
Industrial gases