LIQUID NITROGEN

Source: Hindu

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Context

• A video of a boy screaming in pain after consuming a ‘smoking’ biscuit that went viral has led to the Food Safety department issuing an order on the use of liquid nitrogen.
• The department instructed the Designated Officers and Food Safety Officers “to take enforcement action as per Food Safety and Standards Act 2006 against any Food Business Operator who is using liquid nitrogen for direct consumption along with food items like biscuit, ice creams, wafer biscuits, etc.

Details

• Liquid nitrogen is a colorless, odorless, non-toxic, and non-flammable cryogenic liquid with the chemical formula N2.
• It is derived from the liquefaction of nitrogen gas, which makes up about 78% of the Earth's atmosphere.
• Liquid nitrogen is widely used in various industrial, scientific, culinary, and medical applications due to its unique properties and extremely low temperature.

Properties of Liquid Nitrogen

• Temperature: Liquid nitrogen has an extremely low boiling point of -196°C, making it one of the coldest substances on Earth.
• Density: It has a density of approximately 0.808 grams per milliliter (g/mL) at its boiling point.
• Expansion Ratio: Liquid nitrogen expands about 694 times in volume when it vaporizes to gas at room temperature.
• Reactivity: It is relatively inert and non-reactive under normal conditions, but it can react violently with certain materials at high temperatures.
• Non-toxicity: Liquid nitrogen is generally safe to handle in well-ventilated areas, although it can displace oxygen in confined spaces, leading to asphyxiation.

Production

• Liquid nitrogen is typically produced through a process called cryogenic distillation, which involves compressing and cooling nitrogen gas until it liquefies. The main steps in the production process include:
• Compression: Nitrogen gas is compressed to increase its pressure.
• Cooling: The compressed gas is cooled to very low temperatures, typically using a heat exchanger or Joule-Thomson expansion.
• Separation: At low temperatures, nitrogen gas liquefies while other gases remain in the gaseous state. The liquid nitrogen is then collected and stored in insulated containers.

Applications

• Cryogenics: Liquid nitrogen is extensively used in cryogenic applications, including cryopreservation of biological samples, cryotherapy for medical treatments, and superconductivity research.
• Food Industry: It is used for freezing and preserving food products, such as in the rapid freezing of foods like ice cream or in cryogenic grinding.
• Metal Processing: Liquid nitrogen is employed in metalworking processes, such as cryogenic cooling during machining or in the production of high-strength steel alloys.
• Healthcare: In medicine, liquid nitrogen is utilized in dermatology for cryosurgery to remove warts, skin tags, and certain types of skin cancers.
• Research and Development: It serves as a coolant for various laboratory equipment, such as nuclear magnetic resonance (NMR) spectrometers, electron microscopes, and particle accelerators.
• Industrial Applications: Liquid nitrogen finds applications in industrial processes like inert gas blanketing, purging, and as a coolant for electronic components during manufacturing.

About Nitrogen

• Nitrogen is a chemical element with the symbol N and atomic number 7.
• It is a colorless, odorless, and tasteless gas that makes up about 78% of Earth's atmosphere by volume.
• Nitrogen is the sixth most abundant element in the universe and plays a crucial role in various biological, industrial, and environmental processes.

Properties of Nitrogen:

• Nitrogen is typically found in a gaseous state under normal atmospheric conditions.
• Nitrogen is relatively inert and forms diatomic molecules (N2), which are stable and do not readily react with other elements. However, nitrogen can form compounds with certain elements under specific conditions.
• Nitrogen has a boiling point of -196°C and a melting point of -210°C, making it a cryogenic liquid at low temperatures.
• Nitrogen gas has a density of approximately 1.25 grams per liter under standard conditions.
• Nitrogen is sparingly soluble in water, but it can dissolve in some organic solvents.

Occurrence:

• Earth's atmosphere is composed mainly of nitrogen gas (N2), accounting for approximately 78% of its volume. Nitrogen is obtained from the air through processes such as fractional distillation or cryogenic separation.
• Nitrogen is also produced industrially through the fractional distillation of liquefied air, a process that separates nitrogen from other gases like oxygen and argon.

Applications:

• Fertilizers: Nitrogen compounds such as ammonia (NH3) and urea (CO(NH2)2) are essential components of fertilizers, which are used to improve soil fertility and promote plant growth.
• Chemical Manufacturing: Nitrogen is a key raw material in the production of various chemicals, including ammonia, nitric acid (HNO3), and nitrogenous fertilizers.
• Food Preservation: Nitrogen gas is used in food packaging and storage to create a controlled atmosphere that extends the shelf life of perishable products by inhibiting microbial growth and oxidative reactions.
• Medical Applications: Liquid nitrogen (N2) is used in cryotherapy for medical treatments such as the removal of warts, skin tags, and certain skin lesions.
• Electronics Industry: Nitrogen gas is employed for inerting and purging processes in the electronics industry to prevent oxidation and contamination during the manufacturing of semiconductors and electronic components.
• Metallurgy: Nitrogen is used as a shielding gas in welding and as a heat treatment atmosphere in metallurgical processes to prevent oxidation and improve the mechanical properties of metals.

Environmental Impact:

• Excessive use of nitrogen fertilizers in agriculture can lead to environmental pollution, including water contamination through runoff and eutrophication of aquatic ecosystems.
• Nitrous oxide (N2O), a byproduct of agricultural activities and industrial processes, is a potent greenhouse gas that contributes to global warming and climate change.
• Biological processes such as nitrogen fixation by certain bacteria play a crucial role in converting atmospheric nitrogen into forms that can be utilized by plants, thereby sustaining ecosystems and agricultural productivity.

Sources:

Hindu

PRACTICE QUESTION Q.  Liquid nitrogen is indispensable for numerous scientific, medical, and industrial processes. Comment. (250 words)