People often use liquid nitrogen as a freezing agent for preparing food, preserving medical samples and removing diseased tissue. Liquid nitrogen boils at minus 320.4 degrees Fahrenheit at atmospheric pressure. Manufacturers produce this cryogenic liquid by distilling air.
Liquid nitrogen freezes food almost instantly. Some processors use it in the production of individually packed quick-frozen foods. However, liquid nitrogen is somewhat self-limiting in its freezing ability. Submersing a warmer object in the liquid causes it to boil instantly, forming insulating gaseous bubbles around the object. For even faster freezing of objects, producers have the option of compressing the gas to form a slushy solid. Submersing objects in the slush causes them to freeze before the insulating gas layer forms.
In medicine, personnel often use liquid nitrogen to preserve blood, tissue and other biological specimens collected. The instant-freezing process prevents degradation of the sample, allowing a more accurate diagnosis. Cryogenic freezing of diseased tissue provides a minimally invasive method of removal.
Industries use liquid nitrogen to cool sensitive equipment, such as vacuum pumps and semiconductors. They use the liquid to cool some products that are easier to machine when extremely cold.
The cold of liquid nitrogen can cause immediate frostbite to human skin. Because the liquid boils at room temperature, it builds pressure rapidly in closed containers, creating an explosion hazard.