What Are the Major Uses of Nitric Acid in Fertilizers Explosives and Metal Processing
Nitric acid is commonly known as aqua fortis or spirit of nitre. It is represented by the chemical formula of HNO3. It is a very strong oxidizing agent and a super-strong corrosive mineral acid. It is a colourless acid but older samples will acquire a yellow cast due to the formation of oxides of nitrogen. Commercially available nitric acid is concentrated up to 68% w/w. This means that 68 grams of nitric acid are dissolved in 100 ml of water.
Nitric acid is an important laboratory reagent used for nitration- the addition of the nitro group to an organic molecule. There are other varied uses of nitric acid in the industrial sector. Talking about its chemical structure, nitric acid is an example of a monobasic acid.
Formula: HNO3
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What is the Nitric Acid Density, Boiling Point and Melting Point?
Density: 1.51 g/cubic cm
Boiling point: 83℃
Melting point: -42℃
Areas of Application of Nitric Acid
There are many important uses of HNO3. These are as follows-
In fertilizers: Nitric acid is a very important compound used in the production of different kinds of fertilizers. Nitrogenous fertilizers are one of the main categories of fertilizers for example calcium nitrate, ammonium nitrate, etc. Nitric acid is used to manufacture these compounds. Nitrogen is one of the primary nutrients that is required by plants. It plays a very crucial role in plant physiology and hence plants require an excessive amount of nitrogen as compared to other elements. Hence nitrogenous fertilizers are of vital importance to agriculture and farming.
The precursor to nitro organic compounds: Nitric acid is used for the nitration of several organic compounds. The nitro group is a very versatile functional group by which many explosives such as TNT is prepared. This group is added to aromatic compounds by using a mixture of nitric acid and sulfuric acid.
C6H5CH3 + 3HNO3 🡪 C6H2(NO2)3CH3+ 3H2O
The above mentioned is the chemical equation for the preparation of the explosive TNT.
Polymer synthesis: Nitric acid is the raw material for the synthesis of many chemical compounds. Polymers like polyamines and polyurethane are few compounds that essentially require nitric acid for their synthesis. Certain polymerization reactions take place only in presence of a nitric acid medium.
Rocket propellant: Nitric acid is used as a rocket propellant in the aerospace industry. This form of nitric acid is known as the red fuming nitric acid which is a storable oxidizer. It contains 84 % nitric acid, 13% dinitrogen tetroxide and 1 to 2% of water.
As an oxidant: Nitric acid is a very strong oxidizing agent hence used as an oxidant. Adipic acid which is a precursor to the polymer nylon is produced on a very large scale by the oxidation of KA oil which is a mixture of cyclohexanone and cyclohexanol by nitric acid. The function of nitric acid here is to oxidize the oil to yield adipic acid.
Manufacture of various industrial products: Nitric acid is used for the production of various industrial products like nitrate salts, dyes, coal tar products, various drugs.
In preparation of aqua regia: Aqua regia is a yellow fuming liquid made by mixing concentrated nitric acid and concentrated hydrochloric acid in ratio 1:3. It can dissolve noble metals like gold and platinum hence it is used in the purification of gold and platinum and also in jewellery making.
Nitric acid uses at home: Directly nitric acid is not used in our daily life owing to its extreme power of corrosion and harmful effects on human tissue. Instead, the products manufactured from nitric acid like various medicines, cleansers, fertilizers for the garden are used in our homes on a daily basis. Uses of nitric acid in our daily life can be said as a laboratory school reagent. Dilute nitric acid is used in the woodworks and carpentry to fabricate a maple and pine wood log for giving them an old look. Nitric acid is used in the spot test of alkaloids like LSD which is known as the colourimetric test.
Nitric acid medical use: Nitric acid is used to prepare homoeopathic medicines through a process called potentization. There are drugs that cure throat sore and tonsillitis, mouth ulcers, piles and skin issues.
Interesting Facts About Nitric Acid
Nitric acid is produced by the process called the Ostwald process. This was discovered during the time of the first World War and was a reason behind the extension of the war. This was because Germany had no method of producing nitric acid which was essential for the production of explosives used in the artillery shells like nitroglycerin and nitrotoluene. Nitrates are available only from Guano islands in the form of droppings of fish-eating birds. Hence another method to make nitric acid was essentially required.
Nitric acid is an extremely corrosive acid and can cause irreparable burns on the skin. It burns the human tissue. It should be handled under expert supervision at school or other places. It should be kept out of reach of students. The concentrated form of the acid is usually not used for demonstration in schools as it is more corrosive as compared to the dilute form.
FAQs on Uses of Nitric Acid in Chemistry and Industry
1. What are the main uses of nitric acid?
The main uses of nitric acid (HNO3) are in the manufacture of fertilizers, explosives, dyes, and metal processing.
- Fertilizers: Production of ammonium nitrate (NH4NO3).
- Explosives: Manufacture of TNT, nitroglycerin, and nitrocellulose.
- Metal treatment: Cleaning, pickling, and etching of metals.
- Chemical synthesis: Preparation of nitrates and organic nitro compounds.
2. Why is nitric acid used in the manufacture of fertilizers?
Nitric acid is used in fertilizers because it reacts with ammonia to form ammonium nitrate (NH4NO3), a nitrogen-rich fertilizer. The key reaction is:
NH3(g) + HNO3(aq) → NH4NO3(aq).
- Ammonium nitrate provides nitrogen in a form plants can easily absorb.
- Nitrogen is essential for protein synthesis and plant growth.
- This process is a major industrial use of nitric acid worldwide.
3. How is nitric acid used in making explosives?
Nitric acid is used in explosives through nitration reactions, where nitro groups (–NO2) are introduced into organic compounds.
- TNT (trinitrotoluene): Produced by nitrating toluene.
- Nitroglycerin: Formed by reacting glycerol with nitric acid.
- Nitrocellulose: Made by nitrating cellulose.
4. What is the role of nitric acid in metal cleaning and pickling?
Nitric acid is used in metal cleaning because it dissolves oxides and impurities from metal surfaces.
- It removes rust such as iron(III) oxide (Fe2O3).
- It is used in pickling stainless steel to remove surface contaminants.
- It can oxidize metals like copper:
3Cu(s) + 8HNO3(dil) → 3Cu(NO3)2(aq) + 2NO(g) + 4H2O(l).
5. Why is nitric acid called a strong oxidizing agent?
Nitric acid is called a strong oxidizing agent because it readily accepts electrons and oxidizes many metals and non-metals.
- It can oxidize copper, silver, and other less reactive metals.
- Unlike HCl or dilute H2SO4, it usually does not produce hydrogen gas with metals.
- Reduction products include NO2, NO, or N2O depending on concentration.
6. How is nitric acid used in the production of dyes and drugs?
Nitric acid is used in dyes and pharmaceuticals through nitration of aromatic compounds.
- It introduces the nitro group (–NO2) into benzene rings.
- Nitro compounds can be further reduced to amines, which are key intermediates in dye and drug synthesis.
- This reaction is essential in manufacturing synthetic colors and medicinal compounds.
7. What are the laboratory uses of nitric acid?
In the laboratory, nitric acid is used as a reagent, oxidizing agent, and cleaning agent.
- Preparation of nitrate salts such as AgNO3.
- Qualitative analysis and sample digestion.
- Cleaning glassware by removing organic residues.
8. How is nitric acid used in the preparation of nitrate salts?
Nitric acid is used to prepare nitrate salts by reacting with metals, metal oxides, or carbonates. Examples include:
- With copper: 3Cu(s) + 8HNO3(dil) → 3Cu(NO3)2(aq) + 2NO(g) + 4H2O(l).
- With calcium carbonate: CaCO3(s) + 2HNO3(aq) → Ca(NO3)2(aq) + CO2(g) + H2O(l).
9. Can nitric acid be used in gold purification?
Nitric acid is used in gold purification because it dissolves silver and base metals but not gold.
- Gold is resistant to nitric acid alone.
- Silver reacts to form silver nitrate: Ag(s) + 2HNO3(conc) → AgNO3(aq) + NO2(g) + H2O(l).
- This process helps separate gold from impurities.
10. What safety precautions are required when handling nitric acid?
Nitric acid must be handled with strict safety precautions because it is a corrosive and highly oxidizing acid.
- Wear gloves, goggles, and a lab coat.
- Use in a well-ventilated area or fume hood.
- Avoid contact with organic materials and reducing agents.
- In case of skin contact, rinse immediately with plenty of water.
