Liquid nitrogen is a transparent substance with a specific gravity of 0.808 g / cm³. This is one of the states of aggregation in which nitrogen can be located; its boiling point is −195.75 C. Liquid nitrogen is not toxic and explosion-proof.
A feature of the operation and storage of liquid nitrogen is that when heated, it expands very much, for example, when the temperature rises to only 20 C, about 700 liters of gas are formed from one liter of substance. Therefore, for storage and transportation of it special containers are used, the so-called Dewar vessels, which provide vacuum insulation.
Liquid nitrogen has found quite wide application in various fields of human activity, in many ways, such a breadth of use is due to a property such as the temperature of liquid nitrogen. It is used in industry where the use of cryogenic metal cutting technologies is necessary. The very low temperature of liquid nitrogen allows it to be used for deep freezing, and in this area it is suitable for both inorganic materials and organic, including living organisms.
There are other areas of application: fire fighting and cooling of various units and technical devices, cryopreservation of cells, overclocking.
At atmospheric pressure, the temperature of liquid nitrogen is lower than the oxygen condensation temperature by 10 degrees, therefore, as a rule, a precipitate of the substance condensate can be observed on the walls of the vessels.
Due to the fact that the boiling point of nitrogen in the liquid state is - 195.8 C, which is lower than the same indicator for liquid oxygen, in which it is - 183 C, as a result of their interaction, the liquid air is very rapidly enriched with oxygen. The same temperature difference also explains the more intense evaporation of liquid nitrogen, compared with liquid oxygen.
Almost any temperature that exceeds the figure for liquid nitrogen can be observed during the following experiment. This requires an aluminum block that cools if it is gradually dripped with liquid air.
In modern technologies, the temperature of liquid nitrogen, as the main property of this substance, has led to the widespread use in the electronic and electrical industries of semiconductors, which thereby receive reliable cooling.
The use of the substance as a component of various fire fighting mixtures is based on the same principle. In the process of extinguishing, nitrogen evaporates very quickly and, thereby, displaces oxygen, as a result of the cessation of oxygen access to the source of ignition, the fire is localized and stops completely. Due to this effect, nitrogen fire extinguishing is now recognized as more effective than carbon dioxide. Using such technologies, a high degree of conservation of material values is achieved.
In general, the effect of liquid nitrogen can be observed by almost everyone if he turns his attention to the film effects used in filming modern films. For example, in the movie “Terminator”, effects obtained using liquid nitrogen are widely used (frames that show instant freezing of objects). But such an effect may have a much more familiar embodiment. For example, the low temperature of nitrogen allows it to be used for quick frosts of anesthetic nature. We can often observe this during sporting events, when an athlete is injured and he is given first aid with local aerosol anesthesia.
More exotic, if not fantastic, is the use of the substance as a means of freezing living things, with the aim of defrosting them later, and preserving biological properties.
At the same time, in the USA and in Russia, there are already companies that are engaged in the cryogenic freezing of people and animals on a commercial basis.