Uses of Nitric Acid

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

[Image will be uploaded soon]

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.