Liquid nitrogen
The development of pressurised super-insulated vacuum vessels has enabled liquid nitrogen to be stored and transported over longer time periods with losses reduced to 2 percent per day or less.
Further, its ability to maintain temperatures far below the freezing point of water, specific heat of 1040 J⋅kg−1⋅K−1 and heat of vaporization of 200 kJ⋅kg−1 makes it extremely useful in a wide range of applications, primarily as an open-cycle refrigerant, including: The culinary use of liquid nitrogen is mentioned in an 1890 recipe book titled Fancy Ices authored by Agnes Marshall,[14] 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.
[14] The technique is employed by chef Heston Blumenthal who has used it at his restaurant, The Fat Duck, to create frozen dishes such as egg and bacon ice cream.
[16] It is also added to drinks to create a smoky effect, which occurs as tiny droplets of the liquid nitrogen come into contact with the surrounding air, condensing the vapour that is naturally present.
[18] In January 2021, a line carrying liquid nitrogen ruptured at a poultry processing plant in the U.S. state of Georgia, killing six people and injuring 11 others.
However, a small splash or even pouring down skin will not burn immediately because of the Leidenfrost effect, the evaporating gas thermally insulates to some extent, like touching a hot element very briefly with a wet finger.
[20][21][22] Oxygen sensors are sometimes used as a safety precaution when working with liquid nitrogen to alert workers of gas spills into a confined space.
The liquid in such a vessel becomes increasingly enriched in oxygen (boiling point 90 K; −183 °C; −298 °F) as the nitrogen evaporates, and can cause violent oxidation of organic material.
In 1997, a physics student demonstrating the Leidenfrost effect by holding liquid nitrogen in his mouth accidentally swallowed the substance, resulting in near-fatal injuries.
