Nitric acid has a wide range of industrial applications, although it’s primarily used in the manufacture of fertilisers as a precursor to ammonium nitrate. In fact, fertiliser production accounts for around 80% of the total global use of nitric acid. The chemical is also used to manufacture furniture coatings and certain types of plastics.
Continue reading to learn more about the commercial and industrial uses of nitric acid, as well as the potential hazards.
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What is nitric acid?
Nitric acid is a strong, inorganic mineral acid. Although generally colourless as an aqueous solution, it can sometimes turn yellow over time. This yellowish shade develops as a result of the nitrogen oxides that are produced when the solution decomposes.
Typically, nitric acid is commercially sold as a 68% solution in water, but higher concentrations are also available. These more concentrated solutions are known either as red fuming nitric acid (with a concentration of 86% and above) or white fuming nitric acid (above 95% concentration).
In industry, nitric acid is used as both a reagent for nitration and as an oxidising agent. As a reagent, it can add a nitro group to an organic molecule. Depending on the type of organic molecule, it can either be used to produce thermally-sensitive explosives or stable compounds like the pigments in inks and dyes.
Is nitric acid dangerous?
Nitric acid is dangerous because, just like other strong acids, it’s highly corrosive. It can burn your skin upon contact, especially at high concentrations. Nitric acid fumes can also damage the eyes and mucous membranes in the respiratory tract.
When inhaled, nitric acid may lead to delayed pulmonary oedema. This is a potentially life-threatening condition that causes fluid to build up in the lungs, making it more difficult to breathe. Nitric acid fumes can also cause other types of acute respiratory illnesses such as bronchitis (inflammation of the bronchi).
What is the chemical formula for nitric acid?
Nitric acid has the chemical formula HNO3. As shown in the diagram below, it has one central nitrogen atom, three oxygen atoms, and one hydrogen atom. One of the oxygen atoms is double-bonded to the central nitrogen atom, while the other two are single-bonded. The hydrogen atom is attached to one of the oxygen atoms.
Uses of nitric acid
As we explain below, nitric acid has a variety of applications. It’s mainly used to produce ammonium nitrate for fertilisers, although it can also act as a protective wood coating and a general laboratory reagent.
1. To create ammonium nitrate
Nitric acid is primarily used to produce ammonium nitrate (NH₄NO₃), a key component in fertiliser production. Ammonium nitrate is a salt product that’s produced by the neutralisation reaction between ammonia and nitric acid. The balanced chemical reaction is shown below.
HNO3 + NH3 → NH4NO3
In addition to fertilisers, ammonium nitrate is also used to manufacture other products like nylon. You can read more about the reaction between nitric acid and ammonia here.
2. Furniture coating
Nitric acid is sometimes applied to wooden furniture as it acts as a protector against dents, scratches, and damage from moisture. The furniture is coated with a nitric acid solution and left to dry. The acid then reacts with the cellulose, creating a protective layer that prevents moisture from infiltrating the wood. Nitric acid can also be used to artificially age woods like maple and pine.
3. Chemical laboratory operations
Nitric acid is one of the most common chemicals found in commercial and school chemistry laboratories. Whether for analytical or educational purposes, it’s essential for a range of chemical laboratory operations. Nitric acid can also be used as a pH buffer and cleaning agent.
4. Plastic & packaging manufacturing
About 3% of the total production of nitric acid is dedicated to making polymer intermediates, particularly polyamides. These chemicals are necessary for the production of plastic and other packaging materials like polyurethanes.
5. Fertiliser & gardening chemicals
Nitric acid is neutralised by ammonia to produce ammonium nitrate – a primary ingredient in many fertilisers and chemically-based gardening and agricultural products. According to some estimates, around 80% of industrially-produced nitric acid is used to manufacture nitrate-based fertilisers.
6. Drug detection
Nitric acid is sometimes used to detect and identify certain drugs. For example, it can act as an indicator to differentiate between heroin and morphine. It’s also capable of identifying LSD. In addition, nitric acid can be used as an assay in colourimetry to measure the spectral absorbance of the compounds being analysed.
What are the hazards of using nitric acid?
Highly-concentrated nitric acid solutions are very corrosive and can burn your skin upon contact. The chemical also releases hazardous fumes which, if inhaled, may damage your lungs and respiratory system. It’s therefore important to take proper safety precautions and wear appropriate PPE when handling nitric acid.
What neutralises nitric acid?
In industrial applications, ammonia is commonly used to neutralise nitric acid to produce ammonium nitrate. Ammonia is a weak base that produces an acidic salt. However, a strong base like sodium hydroxide can completely neutralise nitric acid, producing sodium nitrate and water. The balanced chemical equation for this reaction is shown below.
NaOH + HNO3 → NaNO3 + H2O
Summary
Nitric acid is a strong inorganic acid that has several industrial and commercial applications. It’s most commonly used to manufacture fertilisers, acting as a precursor for ammonium nitrate. Uses of nitric acid also include making certain types of plastics and protecting wooden furniture. The substance is commonplace in chemical laboratories, where it’s primarily used for analytical purposes. At high concentrations, nitric acid is very corrosive and should be handled with care.
