Liquid Nitrogen Dewar

Nitrogen constitutes 78% of the Earth’s atmosphere, and under normal conditions it exists as a colourless, odourless and tasteless gas. However, when its temperature is reduced below -196°C, it condenses and becomes a liquid. Liquid nitrogen has been put to many uses, including in cryotherapy to freeze off skin lesions, cooling supercomputers and cryogenic freezing of organisms in the hope of later revival. Although liquid nitrogen boils at temperatures above -196°C, it can be kept as a liquid for long periods (up to a few weeks) in vacuum flasks, usually referred to as ‘dewars’. The liquid inside maintains itself at a very low temperature by slowly boiling off nitrogen gas.