Argon
Argon was suspected to be
present in air by Henry
Cavendish in 1785
but wasn't discovered until 1894
by Lord
Rayleigh and Sir William
Ramsay.
Argon is the third noble
gas, in period 8, and it makes up about 1% of the Earth's
atmosphere.
Argon has
approximately the same
solubility as Oxygen
and it is 2.5 times as soluble
in water as Nitrogen
.
This chemically inert
element is colorless and odorless in both its liquid and gaseous forms.
It is not found in any compounds.
This gas is isolated through
liquid air fractionation since the atmosphere
contains only 0.94% Argon. The Martian
atmosphere in contrast contains 1.6% of Ar-40 and 5 ppm
Ar-36. World production exceeds 750.000 tonnes per year, the supply
is virtually inexhaustible.
Applications
Argon does not
react with the filament in a
lightbulb even under high temperatures
, so is used in lighting and
in other cases where diatomic Nitrogen is
an unsuitable (semi-)inert
gas.
Argon is perticularly important for the metal industry, being used as an inert gas shield in arc
welding and cutting. Other uses incude non-reactive blanket in the manufacture of Titanium
and other reactive elements and as a protective atmosphere for growing Silicon
and Germanium crystals.
Argon-39 has been used for a number of applications, primarily ice
coring. It has also been used for ground
water dating. Argon is also used in technical SCUBA
diving to inflate the drysuit, due to its nonreactive, heat isolating
effect.
Argon as the gap between the panes of glass provides better insulation
because it is a poorer conductor of heat than ordinary air. The most
exotic use of Argon is in the tyre of luxury cars.
Argon in the environment
In earth's atmosphere, Ar-39
is made by cosmic
ray activity, primarily with Ar-40. In the subsurface envIronment,
it is also produced through neutron-capture
by K-39 or alpha emission by Calcium.
Argon-37 is produced from the decay of Calcium-40, the result of
subsurface nuclear
explosions. It has a half-life of 35 days.
Argon is present in some Potassium minerals because
of radiactive decay of the isotope
Potassium
-40
Routes
of exposure:
The substance can be absorbed into the body by
inhalation.
Inhalation
risk:
On loss of containment this
liquid evaporates very quickly causing supersaturation of the air with
serious risk of suffocation when in confined areas.
Effects
of exposure:
Inhalation: Dizziness. Dullness. Headache.
Suffocation. Skin: On contact with liquid: frostbite. Eyes: On contact
with liquid: frostbite.
Inhalation:
This gas is inert and is classified as a simple asphyxiant. Inhalation
in excessive concentrations can result in dizziness, nausea, vomiting,
loss of consciousness, and death. Death may result from errors in
judgment, confusion, or loss of consciousness which prevent self-rescue.
At low Oxygen concentrations, unconsciousness and death may occur in
seconds without warning.
The effect of simple
asphyxiant gases is proportional to the extent to which they diminish
the amount (partial pressure) of Oxygen in the air that is breathed. The
Oxygen may be diminished to 75% of it's normal percentage in air before
appreciable symptoms develop. This in turn requires the presence of a
simple asphyxiant in a concentration of 33% in the mixture of air and
gas. When the simple asphyxiant reaches a concentration of 50%, marked
symptoms can be produced. A concentration of 75% is fatal in a matter of
minutes.
Symptoms:
The first symptoms produced by a simple asphyxiant
are rapid respirations and air hunger. Mental alertness is diminished
and muscular coordination is impaired. Later judgment becomes faulty and
all sensations are depressed. Emotional instability often results and
fatigue occurs rapidly. As the asphyxia progresses, there may be nausea
and vomiting, prostration and loss of
consciousness, and finally convulsions, deep coma and death.
No known ecological damage
caused by Argon.
No adverse Environmental
consequences are expected. Argon gas occurs naturally in the
envIronment. The gas will dissipate rapidly in well ventilated
areas.
The effects of Argon on plants
or animals is not currently known. It is not expected to harm aquatic
life.
Argon does not contain any
ozone depleting chemicals and is not listed as a marine pollutant by DOT
(Department of Transportation, USA).
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