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What are the applications of liquid nitrogen?

Applications of Liquid Nitrogen in Industry and Biology

In industrial applications, liquid nitrogen obtained through the fractional distillation of compressed liquid air serves various purposes. Due to its chemical inertness, it can be used as a deep refrigerant without compromising the biological activity of tissues. Its applications include rapid freezing and transportation of food, low-temperature physics research, demonstrations of low-temperature states in scientific education, and providing the necessary temperature for displaying the superconductivity of high-temperature superconductors.

Furthermore, liquid nitrogen finds use as a refrigerant in quickly freezing biological tissues to prevent damage, in the production of nitrogen fertilizer, and in chemical detection methods such as BET specific surface area testing.

In the field of biology and medicine, liquid nitrogen plays a crucial role. It is utilized to exterminate red fire ants, aid in hemostasis and the insertion of -170°C needles into cancerous tissues during surgical procedures, and freeze cancer cells beneath the skin's surface, eliminating the need for excision of superficial areas.

Moreover, liquid nitrogen is employed for preserving live tissues, biological samples, as well as storing sperm and eggs. Its introduction includes its characteristics: being an inert, colorless, odorless, non-corrosive, non-flammable liquid with extremely low temperatures. Nitrogen constitutes a significant portion of the atmosphere (78.03% by volume, 75.5% by weight) and is non-reactive, not supporting combustion.

At atmospheric pressure, the temperature of liquid nitrogen is -196°C, and it expands from 1 cubic meter to 696 cubic meters of pure gaseous nitrogen at 21°C. Liquid nitrogen is a colorless, tasteless liquid and gas at low temperatures and high pressure. In industry, it is obtained through the air separation process, purifying and pressurizing air, followed by liquefaction in a cooled environment based on the different boiling points of air components. Liquid nitrogen is produced by fractionating air, where nitrogen gas (78.09% of air volume) is the first to escape, followed by rare gases (0.93% of air), and finally, oxygen (20.95% of air).

Direct contact with liquid nitrogen on the skin is initially safe, with frostbite only occurring after more than 2 seconds, and it becomes irreversible.