Argon

PHYSICAL CONSTANTS
  U.S. Units SI Units
Chemical formula Ar Ar
Molecular weight 39.95 39.95
Density of gas    
at 70oF (21.1oC) and at 1 atm 1.38 1.38
Boiling Point at 1 atm -302.60oF -185.9oC
Critical tempreture -188.1oF -122.3oC
Triple Point -308.8oF -189.3oC
Weight of the liquid at boiling point 11.63 lb/gal 1394.40 kg/m3
     

 

DESCRIPTION

 

Argon belongs to the family of inert, rare gases of the atmosphere. It is plentiful compared to the other rare atmospheric gases; 1 million ft3 (28,300 m3) of dry air contains 9,340 ft3 (264m3) of argon. Argon is colourless, odourless, tasteless, and nontoxic. It is extremely inert and forms no known chemical compounds, It is slightly soluble In water.

 

 

GRADES AVAILABLE

 

Gaseous argon is referred to as Type I and liquid argon as Type II.

 

A blank indicates no maximum limiting characteristic. The absence of a value In a listed grade does not mean to imply that the limiting characteristic is or Is not present, but merely indicates that the test Is not required for compliance with the specification.

 

 

USES

 

Argon extensively used in filling incandescent and fluorescent lamps, and electronic tubes; as an Inert gas shield for arc welding and cutting; as a blanket In the production of titanium, zirconium, and other reactive metals; to flush molten metals to eliminate porosity in casting; and to provide a protective shield for growing silicon and germanium crystals.

 

 

PHYSIOLOGICAL EFFECTS

 

Argon Is nontoxic and largely Inert. It can act as a simple asphyxiant by diluting the concentration of oxygen in air below levels necessary to support life. Inhalation of it in excessive concentration can result in dizziness, nausea, vomiting, loss of consciousness, and death. Death may result from errors in judgment, confusion, or toss of consciousness, which prevents self-rescue. At low-oxygen concentrations, unconsciousness and death may occur In seconds without warning.

 

Gaseous argon must be handled with all the precautions necessary for safety as with any nonflammable, nontoxic compressed gas. All precautions necessary for the safe handling of any gas liquefied at very low temperatures must be observed with liquid argon. Extensive tissue damage or burns can result from exposure to liquid argon or cold argon vapours.

 

 

MATERIALS OF CONSTRUCTION

 

Gaseous argon is noncorrosive and inert, and consequently may be contained in systems constructed of any common metals and designed to safely withstand the pressures involved. Satisfactory materials for use with liquid argon include austenitic stainless steel (for example, types 304 and 316), copper, monel, brass, aluminium, and other nickel-chromium alloys.

 

 

SAFE STORAGE, HANDLING AND USE

 

Gaseous argon is commonly stored in high pressure cylinders, tubes, or tube trailers. Liquid argon is commonly stored at the consumer site in cryogenic liquid containers and specially designed vacuum-insulated cryogenic storage tanks.

 

 

DISPOSAL

 

Position discharge valve away from personnel and vent argon gas slowly to well-ventilated outdoor location remote from personnel work area and building air intakes. Return cylinder to the supplier with residual pressure, the cylinder valve tightly closed, and the valve caps in place. Allow liquid argon to evaporate in well-ventilated outdoor locations, which are remote from work area and buildings air Intakes.

 

 

HANDLING LEAKS AND EMERGENCIES

 

Ventilate adjacent ventilated areas to prevent the formation of oxygen-deficient atmospheres caused by the release of gaseous argon or by the evaporation of liquid argon. Personnel, including rescue workers, should not enter areas where the oxygen concentration is below 19% , unless provided with an SCBA or air-line respirator.

 

 

METHODS OF SHIPMENT

 

By highway: In DOT /TC approved cylinders portable tanks, and cargo tanks as a compressed gas; and In cylinders and cargo tanks as a cryogenic liquid.

 

 

CONTAINERS

 

Argon gas is authorised for shipment in cylinders, tube cars, and tube trailers. Liquid argon is shipped as a cryogenic fluid in vacuum- insulated cylinders, insulated portable tanks, insulated tank trucks, and tank cars.

 

 

FILLING LIMITS

 

For gaseous argon, the maximum filling limits authorised are as follows: cylinders and tube trailer may be filled to the authorised service pressure marked on the cylinder or tube assemblies at 70oF (21.1oC).

 

For liquid argon, the maximum filling limits authorised are: specification TC/DOT 4L cylinders are authorised for the transportation of liquid argon when carried in the vertical position. The filling density must be in accordance with Table 3.

 

 

CYLINDERS

 

Cylinders that comply with TC/DOT specifications 3A and 3AA are the types usually used to ship gaseous argon. Liquid argons are authorised for shipment in cylinders that meet TC/DOT specification 4L. For liquid argons at pressures under 25.3 psig, the container specification is not regulated by DOT. All cylinders authorised for gaseous argon service must be re-qualified by hydrostatic retest every 5 to 10 years under present regulations with the following exceptions.

 

 

SMALL PORTABLE CONTAINERS

 

Liquid is shipped and stored in small portable containers (Dewar flasks), which hold quantities form 1 gal to 25 gal (4 L to 95 L) or more. These containers are encased in shells and are heavily insulated; they maintain the liquid at atmospheric pressure.