LIQUID NITROGEN, LN2
Nitrogen N2 Nitrogen is mainly found as a gas in the atmosphere, where it accounts for 78 % by volume.
Nitrogen is also found:
In the Earth's crust, to a limited extent (in the form of nitrates, etc.),
In organic form (in the living or dead plants and organisms which form humus)
In mineral form (ammonia), and thus contributes to soil fertility.
In gaseous form, nitrogen is a neutral, colorless gas. It is inert and does not sustain life.
Handling & Use Liquid Nitrogen, often abbreviated as LN2 is used extensively in all fields of research and industry. The important things to remember is that as a liquid its boiling point is around -195°C (-320°F) at normal pressure which means that unless its temperature is kept below that temperature, it will boil and turn into Nitrogen Gas. Increasing the pressure under which it is stored increases the boiling point. At -147°C (-232.6°F) it reaches the critical temperature above this temperature, the gas cannot be liquefied by pressure alone.
Practically this means that storage of LN2 requires the best heat insulation possible. For this purpose Dewar Flasks or vacuum insulated flasks and containers are used. The Dewar Flask principle is to reduce heat transfer and therefore boiling of the LN2 by minimizing conduction of heat ( the vacuum space and the normal material glass are poor conductors of heat), by minimizing radiation, dewar flasks are coated with silver on their inside walls and by minimizing convection ( the vacuum space has very little gas to allow heat convection .
The main concern in safe handling is to realize that LN2 is very cold and will freeze most items that are placed in it, including human tissue; fingers and such like. The gas boiling off the LN2 is not toxic but will not support life so don't boil LN2 in quantities in small closed spaces. The gas escaping can be very cold and should be handled with care. Use gloves, and eye protection, use proper Dewar Flasks for containing, transport and use of LN2
|Critical temperature||-147 °C|
|Critical pressure||33.999 bar|
|Critical density||314.03 kg/m3|
|Triple point temperature||-210.1 °C|
|Triple point pressure||0.1253 bar|
|Molecular weight||28.0134 g/mol|
|Melting point||-210 °C|
|Latent heat of fusion (1,013 bar, at triple point)||25.73 kJ/kg|
|Liquid density (1.013 bar at boiling point)||808.607 kg/m3|
|Liquid/gas equivalent (1.013 bar and 15 °C (59 °F))||691 vol/vol|
|Boiling point (1.013 bar)||-195.9 °C|
|Latent heat of vaporization (1.013 bar at boiling point)||198.38 kJ/kg|
|Gas density (1.013 bar at boiling point)||4.614 kg/m3|
|Specific gravity (air = 1) (1.013 bar and 21 °C (70 °F))||0.967|
|Specific volume (1.013 bar and 21 °C (70 °F))||0.862 m3/kg|
|Ratio of specific heats (Gamma:Cp/Cv) (1.013 bar and 25 °C (77 °F))||1.403846|
|Thermal conductivity (1.013 bar and 0 °C (32 °F))||24 mW/(m.K)|
|Compressibility Factor (Z) (1.013 bar and 15 °C (59 °F))||0.9997|