Nitric Acid (HNO₃) -- Industrial Applications, Safety & Storage Guide

Nitric acid, with the chemical formula HNO₃, is an important inorganic compound used across many industrial sectors. It is a strong acid with high oxidizing power, widely used in fertilizer manufacturing, explosives production, and metal refining processes.

In this article, Loc Thien Chemical takes a deep dive into what nitric acid is, including the structural formula of HNO3, its physical properties, and its applications in industry and manufacturing. Let's start by looking at what kind of acid HNO3 is, since it is an extremely important compound across many industrial fields.

Chemical Formula of Nitric Acid

The chemical formula of HNO3 is HNO₃, consisting of three main elements: hydrogen (H), nitrogen (N), and oxygen (O). In terms of the structural formula of HNO3, the molecule has a single bond between the nitrogen atom and the hydroxyl group (-OH), plus two double bonds between nitrogen and the remaining oxygen atoms.

• Nitric acid has a molecular weight of 63.01 g/mol and a density of about 1.51 g/cm³. Notably, HNO3 turns yellow because of decomposition that forms NO₂ during prolonged storage.






• The HNO₃ molecule consists of one nitrogen atom bonded to three oxygen atoms and one hydroxyl group (-OH). This structure allows nitric acid to fully dissociate in water, producing H⁺ and NO₃⁻ ions, confirming its nature as a strong acid.






• Under normal conditions, nitric acid is a colorless liquid, but on exposure to light or high temperature it can turn yellow due to the accumulation of nitrogen dioxide (NO₂). The boiling point of HNO₃ is 83°C and its freezing point is -42°C. It is fully soluble in water, forming a strongly acidic solution.

Physical Properties

Nitric acid (HNO3) is a colorless liquid with a strong pungent odor. Under the effect of light or high temperature, HNO3 turns yellow due to the formation of nitrogen dioxide (NO₂). Below are some important characteristics of nitric acid:

• Freezing point: -42°C






• Boiling point: 83°C






• Solubility: Fully soluble in water, forming a strongly acidic solution.

Thanks to these properties, nitric acid is widely applied across many industries.

Manufacturing HNO3

Nitric acid is mainly manufactured through the Ostwald process, an efficient industrial method for producing nitric acid from ammonia (NH3). Below are the basic steps of this process:

1. Oxidation of Ammonia: First, ammonia is mixed with air and then passed through a catalyst (typically platinum or rhodium) at high temperature (around 800-900°C). Here, ammonia reacts with oxygen from the air to form nitric oxide (NO) and water.






2. Oxidation of Nitric Oxide to Nitrogen Dioxide: The nitric oxide is then rapidly cooled and reacts with additional air to form nitrogen dioxide (NO2).






3. Absorption of Nitrogen Dioxide: Nitrogen dioxide is then dissolved in water, producing HNO3. This process usually takes place in an absorption tower, where NO2 reacts with water to produce nitric acid and nitric oxide.






4. Conversion of NO to NO2: Nitric oxide released from the absorption tower can be re-oxidized to NO₂ and recycled back into the process.






5. Purification of Nitric Acid: Finally, the nitric acid is purified by removing impurities and adjusting the concentration to match specific usage requirements.
   The Ostwald process is not only efficient for producing nitric acid but also helps optimize the use of both raw materials and energy.

In industry, nitric acid is mainly produced through the Ostwald process, which includes the following steps:

• Oxidation of Ammonia (NH₃): Ammonia is oxidized into nitric oxide (NO) using a platinum catalyst at high temperature.






• Oxidation of Nitric Oxide: Nitric oxide is further oxidized into nitrogen dioxide (NO₂).






• Absorption of NO₂: NO₂ is dissolved in water, forming nitric acid and releasing some NO, which can be recycled back into the process.

This process allows nitric acid to be produced at high efficiency and is widely applied in the chemical industry.

Applications of Nitric Acid

What is HNO3 used for? It is an extremely important acid with many applications, including:

• Fertilizer Production
  
  
  
  • Nitric acid is the main raw material for producing ammonium nitrate, a key ingredient in many fertilizers.
  
  
  
  






• Metal Refining
  
  
  
  • Nitric acid is used to etch and clean metal surfaces such as gold and silver, through dissolving and separating the metal from ore.
  
  
  
  






• Explosives Manufacturing
  
  
  
  • Nitric acid combined with glycerin forms nitroglycerin, an important component in explosives.
  
  
  
  






• Pharmaceutical and Chemical Industry
  
  
  
  • HNO3 takes part in the synthesis of many important chemical compounds.
  
  
  
  






• Wastewater Treatment and Industrial Cleaning
  
  
  
  • Nitric acid helps remove organic contaminants, a common application in water treatment.
  
  
  
  






• Production of Nitrate Compounds:
  
  
  
  • Used to produce other nitrate compounds such as potassium nitrate and calcium nitrate, which have applications across many different industries.
  
  
  
  

See more applications of HNO3

Safety Precautions When Using Nitric Acid

Because of its corrosive and strongly oxidizing properties, handling and using nitric acid requires strict safety measures:

• Protective Equipment: Always wear gloves, safety goggles, and chemical-resistant clothing when working with HNO₃.






• Storage: Store nitric acid in containers made of corrosion-resistant materials, in a dry, well-ventilated place away from flammable substances.






• Incident Response: If it contacts skin or eyes, rinse immediately with clean water and seek medical attention.

Following these safety measures helps ensure safety for users and the surrounding environment.

Conclusion

Is HNO3 a strong or weak acid? Based on its chemical properties, HNO3 is a strong acid, capable of corroding metals and decomposing organic compounds. Thanks to these properties, it plays an important role in industry and many other fields. The structural formula of HNO3 consists of a nitrogen atom bonded to three oxygen atoms, with one hydroxyl group (-OH). This is also the structural formula of HNO3 that determines the chemical reactions of this acid. Under long-term storage conditions, HNO3 turns yellow due to the gradual decomposition of the compound, forming NO₂ — an important consideration when using nitric acid in laboratories or industrial production.

So what is nitric acid? It is a colorless liquid, with the chemical formula HNO₃, used in fertilizer production, explosives, and industrial chemicals. At Loc Thien Chemical, we supply technical-grade nitric acid suitable for production and research needs. If you need advice or want to buy HNO3, please contact 0979 891 929 for support.

At Loc Thien Chemical, we always deal in products that meet quality standards at reasonable prices. If you need to buy HNO3, buy HCl acid or buy H2SO4 acid, or any other acid you need, please contact us via hotline: 0979 891 929 for detailed advice.