Nitrogen boiling point

The first objective was that of achieving critical temperatures higher than 77 K (—196°C). In this way liquid nitrogen (boiling point 77 K) could be used as the cryogenic liquid instead of the much more expensive and difficult to handle liquid helium. 

Nevertheless it should be borne in mind that the use of liquid fluorine has considerable disadvantages. Its boiling point is — 187°C. To prevent corrosion special vessels of nickel alloys surrounded by a jacket filled with liquid nitrogen (boiling point — 199.5°C) are required. 

For cryogenic temperature measurements, furnaces consist of thermally conductive jackets filled with liquid nitrogen (boiling point 77.35 K) or liquid helium (boiling point 4.215 K). The heat dissipation from resistance heating elements competes with the cooling effects of these fluids to permit stable temperature control down to near absolute zero [10]. 

When cooled to very low temperatures, some materials lose all electrical resistance and exhibit superconductivity. Some alloys are superconductive when cooled in liquid helium (boiling point 4.2 K), but some ceramics are superconductive at higher temperatures and need only be cooled in liquid nitrogen (boiling point 77.3 K) to show this effect. 

When temperatures 80-100 K are required regularly, liquid nitrogen (boiling point 77K) is a convenient cryogenic liquid. 

The heat of vaporization of a liquid (A//yap) is the energy required to vaporize 1.00 g of the liquid at its boiling point. In one experiment, 60.0 g of liquid nitrogen (boiling point — 196°C) are poured into a Styrofoam cup containing 2.00 X 10 g of water at 55.3°C. Calculate the molar heat of vaporization of liquid nitrogen if the final temperature of the water is 41.0°C. 

The sample first had to be frozen as a small droplet (diameter about 1.5 mm) in liquid propane (boiling point 228.6 K, melting point 84.4 K) that was kept around its melting temperature by indirect contact with liquid nitrogen (boiling point 77.3 K). 

---