Photo credit: Mike Walker / Pop Sci
Liquid nitrogen isbasically nitrogen in a liquid state at an extremely low temperature. It’s often referred to by the abbreviation, LN2 or “LIN” or “LN” and has the UN number 1977. Liquid nitrogen is a diatomic liquid meaning the diatomic character of the covalent N bonding in N2 gas is retained even after liquification. At atmospheric pressure, liquid nitrogen boils at −196 °C (77 K; −321 °F) and is a cryogenic fluid that can cause rapid freezing on contact with living tissue. Continue reading for more.
5. Liquid Nitrogen Vehicle
A liquid nitrogen vehicle is powered by liquid nitrogen, which is stored in a tank. Traditional nitrogen engine designs work by heating the liquid nitrogen in a heat exchanger, extracting heat from the ambient air and using the resulting pressurized gas to operate a piston or rotary engine. Vehicles propelled by liquid nitrogen have been demonstrated, but are not used commercially. One such vehicle, Liquid Air was demonstrated in 1902.
4. Liquid Nitrogen Cooking
The culinary use of liquid nitrogen is mentioned in an 1890 recipe book titled Fancy Ices authored by Mrs. Agnes Marshall, but has been employed in more recent times by restaurants in the preparation of frozen desserts, such as ice cream, which can be created within moments at the table because of the speed at which it cools food. The rapidity of chilling also leads to the formation of smaller ice crystals, which provides the dessert with a smoother texture.
3. Liquid Nitrogen Explosion
Because of its extremely low temperature, careless handling of liquid nitrogen may result in cold burns. As liquid nitrogen evaporates it will reduce the oxygen concentration in the air and might act as an asphyxiant, especially in confined spaces. Nitrogen is odorless, colorless, and tasteless and may produce asphyxia without any sensation or prior warning. In 2012, a young woman in England had her stomach removed after ingesting a cocktail made with liquid nitrogen.
2. Liquid Nitrogen Production
Liquid nitrogen is produced commercially from the cryogenic distillation of liquified air or from the liquefication of pure nitrogen derived from air using pressure swing adsorption. An air compressor is used to compress filtered air to high pressure; the high-pressure gas is cooled back to ambient temperature, and allowed to expand to a low pressure. The expanding air cools greatly (the Joule-Thomson effect), and oxygen, nitrogen, and argon are separated by further stages of expansion and distillation.
1. Liquid Nitrogen Boils
Despite its reputation, liquid nitrogen’s 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. This effect, known as the Leidenfrost effect, applies to any liquid in contact with an object significantly hotter than its boiling point. More rapid cooling may be obtained by plunging an object into a slush of liquid and solid nitrogen rather than liquid nitrogen alone.