Liquid nitrogen

It is called liquid nitrogen the nitrogen in a liquid state at an extemly low temperature. Liquid nitrogen is mostly referred by the abbreviation LN2 or “LIN” or “LN” and it is usually produced industrially by fractional distillation of liquid air. The liquid is colourless and it has the density at its boiling point 0.807g/mL and a dielectric constant of 1.4. Nitrogen was first liquefied at the Jagiellonian University on 15 April 1883 by Polish physicists, Zygmunt Wróblewski and Karol Olszewski.

At atmospheric pressure, liquid nitrogen boils at −196 °C (77 K; −321 °F) and is a cryogenic fluid which can cause rapid freezing on contact with living tissue. When appropriately insulated from ambient heat, liquid nitrogen can be stored and transported. Here, the very low temperature is held constant at 77 K by slow boiling of the liquid. Depending on the size and design, the holding time of vacuum flasks ranges from a few hours to a few weeks.

If interested in converting liquid nitrogen  into the solid, the process can be easily done by placing it in a vacuum chamber pumped by a rotary vacuum pump. Liquid nitrogen freezes at 63 K (−210 °C; −346 °F).

Although it has a great reputation, its efficiency as a coolant is limited by the fact that it boils immediately on contact with a warmer object, enveloping the object in insulating nitrogen gas. The effect that is created is known  the Leidenfrost effect and it applies to any liquid in contact with an object significantly hotter than its boiling point.


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