Nitrogen

Chemical Symbol: N2
Proper Shipping Name:                      Nitrogen, Compressed
Nitrogen, Refrigerated Liquid
Classification: 2.2 (Nonflammable Gas)
Label: NON-FLAMMABLE GAS

 
 
 

PHYSICAL CONSTANTS
  U.S. Units SI Units
Chemical formula N2 N2
Molecular weight 28.01 28.01
Specific gravity of the gas at 70oF (21.1oC)    
and 1 atm (air=1) 0.967 0.967
Density of the liquid at boiling point and 1 atm 50.47 lb/ft3 808.5 kg/m3
Critical temperature -232.4oF -146.9oC
Triple point At 1.81 psia or 12.5 kPa, abs -346.0oF -210.0oC
     

 

DESCRIPTION

 
Nitrogen makes up the major portion of the atmosphere (78.08% by volume, 75.5% by weight). It is a colourless, odourless, tasteless, non-toxic, almost totally inert gas, and is colourless as a liquid. Nitrogen is non-flammable, will not support combustion and is not life supporting. It combines with some of the more active metals such as lithium and magnesium to form nitrides, and at high temperatures, it will also combine with hydrogen, oxygen, and other elements. It is used as inert protection against atmospheric contamination in many non-welding applications. Nitrogen is only slightly soluble in water and most other liquids, and is a poor conductor of heat and electricity. As a liquid at cryogenic temperatures it is non-magnetic. It is shipped as a non-liquefied gas at pressures of 2,000 psig (13,790 kPa) or above, and also as a cryogenic fluid at pressures and temperatures below 200 psig (1,380 kPa) and -261oF.

 

USES

 
Nitrogen has many commercial and technical applications. As a gas, it is used in heat treating of primary metals; blanketing of oxygen-sensitive liquids and of volatile liquid chemicals; the production of semiconductor electronic components, as a blanketing atmosphere; the blowing of foam-type plastics; the deaeration of oxygen-sensitive liquids; the degassing of nonferrous metals; food processing and packing; inhibition of aerobic bacteria growth; magnesium reduction of aluminum scrap; and the propulsion of liquids through pipelines. Gaseous nitrogen is also used in pressurising aircraft tires and emergency bottles to operate landing gear; purging, in the brazing of copper tubing for air-conditioning and refrigeration systems; the purging, filling of electronic devices; the purging, filling, and testing of high voltage compression cables; the purging and testing of pipelines and related instruments; and the treatment of alkyd resins in the paint industry.

 

Liquid nitrogen also has many uses, among them are the freezing of highly perishable foods such as shrimp, hamburgers, and chicken; deflashing of rubber tires; cooling of concrete; and the cold trapping of materials such as carbon dioxide from gas streams. It is used as a coolant for electronic equipment, for pulverising plastics, and for simulating the conditions of outer space. Other ways in which liquid nitrogen is used include; creating a very high pressure gaseous nitrogen (15,000 psig or 103,000 kPa) through liquid nitrogen pumping; in food and chemical pulverisation; for freezing of liquids in pipelines for emergency repairs; for low temperature stabilisation and hardening of metals; for low temperature research; for low temperature stress relieving of aluminum alloys; for the preservation of whole blood, livestock sperm, and other biochemical; for refrigerating food in local and long-distance hauling; for refrigeration shielding of liquid nitrogen, helium and neon; for the removal of skin blemishes in dermatology; and for shrink fitting of metal parts.

PHYSIOLOGICAL EFFECTS

 
Nitrogen is non-toxic and largely inert. It can act as a simple asphyxiant by diluting the concentration of oxygen below levels necessary to support life. Inhalation of nitrogen 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 prevents self rescue. At low oxygen concentrations, unconsciousness and death may occur in seconds without warning.

All precautions necessary for the safe handling of any gas liquefied at very low temperatures must be observed with liquid nitrogen. Extensive tissue damage or burns can result from exposure to liquid nitrogen or cold nitrogen vapours.

 

MATERIALS OF CONSTRUCTION

 
Gaseous nitrogen is non-corrosive and inert, and may consequently be contained in systems constructed of any common metals and designed to safely withstand the pressure involved.

 

 

SAFE STORAGE, HANDLING AND USE

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

 

All of the precautions necessary for any nonflammable gas or cryogenic liquid must be taken.

 

DISPOSAL

 
Vent nitrogen gas slowly to a well-ventilated outdoor location, remote from personnel work areas and building air intakes. Return cylinders to the supplier with residual pressure, and with the cylinder valve tightly closed and the valve caps in place.

 

Allow liquid nitrogen to evaporate in well-ventilated outdoor locations that are remote from work areas and building air intakes.

 

HANDLING LEAKS AND EMERGENCIES

 
Ventilate adjacent enclosed area to prevent the formation of oxygen-deficient atmospheres caused by the release of gaseous nitrogen or by the evaporation of liquid nitrogen. Avoid contact of the skin with liquid nitrogen or its cold boil-off gas. Flush liquid nitrogen spills with water to accelerate evaporation.