Liquid Nitrogen Science

Nitrogen is one of the most common naturally occurring elements and is typically found in its gaseous state; it is odorless, colorless and non-reactive. When chilled to extreme temperatures, nitrogen gas condenses and is converted to liquid nitrogen, which has a number of medical and industrial uses. Though liquid nitrogen is quite safe when basic protective guidelines are followed, failure to use proper equipment can result in severe injury.

Liquid Nitrogen Facts
Discovered by Daniel Rutherford in 1772, liquid nitrogen is an extremely cold compound that does not freeze until it reaches temperatures of -346 degrees Fahrenheit. Though most commonly referred to by its common name, liquid nitrogen may also be referred to as LN2, LN, or LIN. In its liquid form, nitrogen has been found to be lighter than water, weighing in at around six pounds per gallon. Though it has been highly prized for its coldness, it also has a high degree of inertness; this helps shield materials that may be potentially reactive from contact with oxygen and is another higher desirable characteristic of the compound.

Uses of Liquid Nitrogen
One of the most common uses of liquid nitrogen is in the field of health care. Cryotherapy is a technique in which skin growths are frozen and removed through the application of liquid nitrogen. Developed in the mid-19th century, cryotherapy has been found to be a highly effective method of eliminating warts, precancerous lesions, and sun spots. In cryotherapy, the area of skin under treatment is sprayed with liquid nitrogen for five to 60 seconds, or until it has been completely covered with ice. The frozen tissue is allowed to thaw, and the process is repeated another two or three times. Eventually, the tissue undergoing cryotherapy will dry up and fall off. Cryotherapy has been found to be most effective for individuals who suffer from warts, sun spots, or precancerous lesions that are less than ten millimeters in diameter, are in an exposed location, do not go away with time or medication, or are causing pain or bleeding.

Liquid nitrogen has also been used in food preservation. Though freezing has always been an effective method of extending the life of perishables, the gradual lowering of temperature by which food traditionally was frozen does not always produce satisfactory results. Upon contact with the perishable item, the liquid nitrogen evaporates, instantaneously absorbing all available heat, and providing a “deep freeze” that may not be obtainable with more traditional methods.   

With energy rates rising significantly in recent years, scientists are searching for ways in which our energy requirements can be decreased. Recently, some researchers found that when metals are cooled to extremely low temperatures, such as those that can be reached when liquid nitrogen is applied, the atoms and molecules found within them stop moving. This results in low resistance levels, and an increased ability of electricity to flow through the metals in question. These increased flow rates may result in lowered energy bills, and potential financial savings.

Finally, liquid nitrogen is also commonly used in theatric experiments and demonstrations to mimic smoke or fog in plays and movies, due to its relative safety and ease of use. Spraying fruits, vegetables, flowers, or pieces of paper with liquid nitrogen, and then dropping them on a hard surface—causing them to shatter into hundreds of pieces—is another popular stage trick that is commonly used by magicians, clowns, and other entertainers. 

Liquid Nitrogen Safety
As with other chemicals, liquid nitrogen can be a very dangerous compound when basic safety measures are not followed. For the best results when using this compound, handlers should always wear goggles, leather gloves, and remove all metal jewelry. Those working with large quantities of liquid nitrogen may want to consider the use of full-length aprons to avoid possible spills and burns. It is recommended that those working with liquid nitrogen have another individual present in the room in case a spill does occur. In the event of a liquid nitrogen burn, emergent medical treatment may be required.