Argon
Overview
Slightly less than one percent of the earth’s atmosphere is composed of argon, which is colorless, odorless, tasteless, and nontoxic. As an inert gas, argon does not react with other compounds or elements. Argon is about 1.4 times heavier than air and cannot sustain life. The inert properties of argon make it ideal as a shield against atmospheric contamination, thus it is used in many welding processes. Argon promotes good arc starting characteristics and arc stability due to its low ionization potential.
Argon Characteristics
Argon has approximately the same solubility in water as oxygen and is 2.5 times more soluble in water than nitrogen. 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, it can form some compounds under various extreme conditions. Argon fluorohydride (HArF), a compound of argon with fluorine and hydrogen that is stable below 17 K (−256.1 °C; −429.1 °F), 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, such as ArH+, and excited-state complexes, such as ArF, have been demonstrated. Theoretical calculation predicts several more argon compounds that should be stable but have not yet been synthesized.
TEchnical Information
Argon Physical Properties
| Formula | Ar |
| Molecular Weight (lb/mol) | 39.95 |
| Critical Temp. (°F) | -188.4 |
| Critical Pressure (psia) | 705.8 |
| Boiling Point (°F) | -302.6 |
| Melting Point (°F) | -308.8 |
| Gas Density @ 70°F 1 atm (lb/ft3) | 0.1034 |
| Specific Volume @ 70°F 1 atm (ft3/lb) | 9.67 |
| Specific Gravity | 1.38 |
| Specific Heat @ 70°F (Btu/lbmol-°F) | 4.98 |
Argon Uses and Applications
Argon is one of the most common carrier gases in gas chromatography. Argon is used as a carrier gas in sputtering, plasma etching and ion implantations, and as a blanket atmosphere in crystal growth.
Argon is also the choice gas for ICP spectroscopy (Inductively Coupled Plasma spectroscopy).
One of the most common applications of argon, either pure or in various mixtures, is as a shielding gas for arc welding.
Many Geiger-counting tubes contain argon or argon mixed with organic vapors or other gases, for example 10% methane in argon.
Argon is one of the principal gases used for filling incandescent (filament) lamps, generally in a mixture with nitrogen, krypton or neon, for phosphorescent tubes in mixtures with neon, helium and mercury vapor and for thyratron radio tubes, in mixtures with neon.
The argon-oxygen decarburizing (AOD) process is the most common method of refining stainless steel, and uses large quantities of both gases supplied either in liquid form or via pipeline from an on-site plant.
The pharmaceutical industry uses argon to displace oxygen in the top of intravenous drug containers, extending product shelf-life
Liquid argon is used in cryosurgery, e.g. cryoablation to destroy cancer cells.
Argon, R-740, is used in gas mixtures for non-CFC ultra-low temperature refrigeration applications.
Argon:
- is used in atomic absorption spectrometry as a blanket gas in the graphite furnace.
- is used in blends with, for example, fluorine and helium in excimer lasers.
- is used as an insulation gas in high-efficiency multi-pane windows to improve thermal insulation.
- is used in the iron and steel industry to prevent oxidation of molten metals and alloys and for degassing and desulphurization of molten steel and iron baths.
- is used, often in a mixture with hydrogen, as a protective atmosphere for the heat treatment of certain metals, particularly those which are susceptible to nitriding when treated in a nitrogen-based atmosphere. This includes stainless steels and many different specialized and therefore small-scale applications.
- is used for wine preservation to eliminate air by the heavier argon, to prevent oxidation and extend the product quality for opened bottles and barrels.
- is, sometimes in combination with nitrogen, used to inflate airbags.
- is used, often in combination with nitrogen and/ or carbon dioxide, as a clean fire extinguishing gas, since the inert properties do not damage any materials extinguished.
- is used in laboratory as purge gas or balance gas in gas mixtures.
Compressed Gas
Argon Purity Grades
| Product/Purity | Purity Percent | Part Number Prefix |
|---|---|---|
| Argon: Research, 6.0 | >99.9999% Oxygen < 0.2 ppm Water < 1 ppm Total Hydrocarbons (as CH4) < 0.1 ppm Nitrogen < 1 ppm Carbon Monoxide < 0.1 ppm Carbon Dioxide < 0.1 ppm | ARG6.0 |
| Argon: Lab & Specialty Grade | >99.9995% Oxygen < 1 ppm Water < 1 ppm Total Hydrocarbons (as CH4) < 0.5 ppm | ARG5.5 |
| Argon: Ultra High Purity, 5.0 | >99.999% Oxygen < 2 ppm Water < 4 ppm Total Hydrocarbons (as CH4) < 1 ppm | ARG5.0 |
| Argon: High Purity, 4.8 | >99.998% | ARG4.8 |
| Argon: Industrial Grade | >99.997% Oxygen < 5 ppm Water < 10.5 ppm Total Hydrocarbons (as CH4) < 1 ppm | ARG |
| Argon: Food Grade | >99.998% Nitrogen + Oxygen < 20 ppm | ARGFG |
Argon Transportation Information
| Proper Shipping Name | ID Number | Hazard Class or Division | Packing Group | Labeling Requirements | Passenger Aircraft or Railcar Quantity Limitations | Cargo Aircraft Only Quantity Limitations | Additional Shipping Description |
|---|---|---|---|---|---|---|---|
| Argon, compressed | UN1006 | 2.2 | Not applicable | 2.2 | 75 kg or L | 150 kg | N/A |
| Argon, Liquid | UN1951 | 2.2 | Not applicable | 2.2 | 75 kg or L | 150 kg | N/A |
Argon Conversion Chart
| Weight | Gas | Liquid | ||||
|---|---|---|---|---|---|---|
| pounds (lb) | kilograms (kg) | cubic feet (scf) | cu meters (Nm3) | gallons (gal) | liters (l) |
|
| 1 pound | 1.0 | 0.4536 | 9.671 | 0.2543 | 0.08600 | 0.3255 |
| 1 kilogram | 2.205 | 1.0 | 21.32 | 0.5605 | 0.18957 | 0.7176 |
| 1 scf gas | 0.1034 | 0.04690 | 1.0 | 0.02628 | 0.008893 | 0.03366 |
| 1 Nm3 gas | 3.933 | 1.7840 | 38.04 | 1.0 | 0.3382 | 1.2802 |
| 1 gallon liquid | 11.630 | 5.276 | 112.5 | 2.957 | 1.0 | 3.785 |
| 1 liter liquid | 3.072 | 1.3936 | 29.71 | 0.7812 | 0.2642 | 1.0 |
| 1 short ton | 2000 | 907.2 | 19342 | 508.6 | 172 | 651.0 |