Argon
Ar

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General Characteristics Health Hazards Material Recommendations

A colorless, nonflammable and odorless gas

A Simple Asphyxiant

Normal materials can be used
TLV-TWA Flammable Limits DOT Class / Label
None Established Nonflammable 2.2 / Nonflammable
Molecular Weight Specific Gravity Specific Volume
39.95 1.378 @ 70 F 9.68 cu.ft./lb @ 70 F
CGA Valve Outlet CAS Registry No. UN Number
580 740-37-1 1006
National Stock Number (NSN) Applicable to Argon MIL Spec / Fed Specs
MSDS for Argon


Grade
Part #
Purity Minimum Cylinder
Size
Volume
SCF
Pressure
@ 70 F
Comments
Research
474300
99.9995% 049
044
002
336
224
4
2640
2000
1800

None

Spectrographic
405500
99.9995% 049
044
LBS
336
224
2
2640
2000
1800

None

Ultra High Pure
401000
99.999% 049
044
LBS
336
224
2
2640
2000
1800

None

Zero
400800
99.998%
<0.5 ppm THC
049
044
LBS
336
224
2
2640
2000
1800

None

High Purity
401100
99.998% 049
044
LBS
336
224
2
2640
2000
1800

None

Prepurified
401200
99.996% 049
044
LBS
336
224
2
2640
2000
1800

None

Industrial / Technical 99.9% 049
044
LBS
336
224
2
2640
2000
1800

None


Uses: Argon is one of the most abundant members of the rare gas family which consists of helium, neon, argon, krypton, and xenon. Here you can review current CGA and MIL Specs for Argon, including a variety of specialty gas grades up to 99.9995% pure. Argon is used extensively in the incandescent lamp industry for the filling of light bulbs. It is used in arc welding, plasma jet torches and several other rare gas mixtures.

General

(Ar), chemical element, inert gas of Group 0 (noble gases) of the periodic table, terrestrially the most abundant and industrially the most frequently used of the noble gases. Colourless, odourless, and tasteless, argon gas was isolated (1894) from air by the British scientists Lord Rayleigh and Sir William Ramsay. Henry Cavendish, while investigating atmospheric nitrogen ("phlogisticated air"), had concluded in 1785 that not more than 1/120 part of air might be some inert constituent. His work was forgotten until Lord Rayleigh, more than a century later, found that nitrogen prepared by removing oxygen from air is always about 0.5 percent more dense than nitrogen derived from chemical sources such as ammonia. The heavier gas remaining after both oxygen and nitrogen had been removed from air was the first of the noble gases to be discovered on Earth and was named argon because of its chemical inertness. (Helium had been spectroscopically detected in the Sun in 1868.)

Argon constitutes 1.3 percent of the atmosphere by weight and 0.94 percent by volume and is found occluded in rocks. A major portion of terrestrial argon has been produced, since the Earth's formation, in potassium-containing minerals by decay of the rare, naturally radioactive isotope potassium-40. The gas slowly leaks into the atmosphere from the rocks in which it is still
being formed. The production of argon-40 from potassium-40 decay is utilized as a means of determining the Earth's age (potassium-argon dating). On Earth, naturally occurring argon is a mixture of three stable isotopes: argon-36 (0.34 percent), argon-38 (0.06 percent), and argon-40 (99.60 percent).

Argon is isolated on a large scale by the fractional distillation of liquid air. It is used in gas-filled electric light bulbs, radio tubes, and Geiger counters. It also is widely utilized as an inert
atmosphere for arc-welding metals, such as aluminum and stainless steel; for the production and fabrication of metals, such as titanium, zirconium, and uranium; and for growing crystals of semi-conductors, such as silicon and germanium.

Argon gas condenses to a colourless liquid at -185.8° C (-302.4° F) and to a crystalline solid at -189.4° C (-308.9° F). The gas cannot be liquefied by pressure above a temperature of -122.3° C (-188.1° F), and at this point a pressure of at least 48 atmospheres is required to make it liquefy. At 12° C (53.6° F), 3.94 volumes of argon gas dissolve in 100 volumes of water. An electric discharge through argon at low pressure appears pale red and at high pressure, steely blue.

The outermost (valence) shell of argon has eight electrons, making it exceedingly stable and, thus, chemically inert. Argon atoms do not combine with one another; nor have they been observed to combine chemically with atoms of any other element. Argon atoms have been trapped mechanically in cagelike cavities among molecules of other substances, as in crystals of ice or the organic compound hydroquinone.

Atomic number 18

Atomic weight 39.948

Melting point -189.2° C (-308.6° F)

Boiling point -185.7° C (-302.3° F)

Density (1 atm, 0 C) 1.784 g/litre

Valence 0

Electronic configuration 2-8-8 or 1s22s22p63s23p6

Last Updated: 7/25/98