Nitrogen (\(\text{N}_2\)) is a colorless, odorless, and tasteless gas that makes up approximately 78% of the Earth’s atmosphere. The two nitrogen atoms are held together by a very strong triple covalent bond, which requires significant energy to break. This powerful bond is responsible for the molecule’s extreme unreactivity, or inertness, under normal conditions. This abundance and chemical stability make nitrogen ideal for applications requiring an atmosphere free of reactive components like oxygen or moisture.
Inerting and Preventing Oxidation
The inert nature of nitrogen gas makes it highly effective for displacing oxygen in industrial environments, a process known as blanketing or purging. By filling the headspace of storage tanks or process vessels, industries eliminate the risk of fire or explosion. This is widely practiced in the petrochemical, oil and gas, and chemical manufacturing sectors to protect volatile liquids from coming into contact with atmospheric oxygen.
This blanket of inert gas is also used to preserve product quality by preventing undesirable chemical reactions like oxidation. In the manufacturing of electronics and semiconductors, nitrogen purging is used within clean rooms and during soldering to ensure sensitive components do not corrode or degrade.
Nitrogen gas is also used in specialized applications like filling aircraft and racing tires. Using nitrogen instead of regular compressed air helps maintain a more consistent tire pressure because nitrogen expands less with temperature changes. It also prevents the slow oxidation of rubber compounds that can lead to material degradation over time.
Cryogenic Applications of Liquid Nitrogen
When cooled to approximately \(-196^\circ\text{C}\) (\(-320^\circ\text{F}\)), nitrogen changes into a clear, colorless liquid (\(\text{LN}_2\)). This extremely cold temperature makes liquid nitrogen a highly effective cryogen used across numerous fields. In medicine and biology, \(\text{LN}_2\) is the standard for cryopreservation, allowing for the long-term storage of biological materials.
Laboratories and biobanks use specialized containers to store sperm, eggs, blood, and tissue samples for decades, as the ultra-low temperature halts all biological activity and degradation. Liquid nitrogen is also used in cryosurgery, where the rapid application of intense cold precisely destroys abnormal or diseased tissue, such as warts or precancerous cells.
Industrially, this deep cold is utilized for processes like cryogenic tempering, where metal components are submerged in \(\text{LN}_2\) to increase their strength and durability. In scientific research, it is used to cool high-speed sensors, detectors, and computer components to reduce thermal noise and improve measurement accuracy.
Food Preservation and Beverage Dispensing
Nitrogen gas plays a significant role in maintaining the quality and extending the shelf life of consumer goods, particularly food and beverages. In the food industry, \(\text{N}_2\) is a primary gas used in Modified Atmosphere Packaging (MAP), replacing the air inside a package with a specific gas mixture. By flushing nitrogen into the packaging, the oxygen concentration is rapidly reduced, dramatically slowing down spoilage.
This process prevents oxidative rancidity in fatty foods, stops color deterioration in meats, and inhibits the growth of aerobic spoilage microorganisms. In flexible packaging, such as bags of potato chips, nitrogen is also used as a harmless filler gas to create a protective cushion, preventing the contents from being crushed during shipping.
In beverage dispensing, nitrogen is used to pressurize kegs of beer or coffee, serving as a propellant that does not chemically alter the flavor of the drink. When dissolved into the liquid, it produces the characteristic fine, dense bubbles found in “nitro” coffee and certain stouts, giving the drink a smoother, velvety mouthfeel.
Role in Chemical Synthesis and Laboratory Work
The chemical reactivity of nitrogen is fundamentally transformed through the high-pressure, high-temperature industrial process known as the Haber-Bosch synthesis. This process combines atmospheric nitrogen with hydrogen to create ammonia (\(\text{NH}_3\)) using an iron-based catalyst.
Ammonia is the foundational ingredient for nearly all synthetic nitrogen fertilizers, which are directly responsible for sustaining a substantial portion of the global population. Annually, over 90 million metric tons of nitrogen fertilizer are produced via this method, underscoring nitrogen’s role as a chemical building block for global food production.
In analytical and laboratory settings, nitrogen is widely used as a specialized tool in its gaseous form. It functions as an inert carrier gas in instruments like gas chromatographs, pushing the sample through the system without reacting with it. It is also used as a purging agent to dry scientific glassware and reaction vessels before sensitive experiments begin.