Nitric acid Manufacturing Process | Uses | Ostwald Process

Nitric acid manufacturing process is started from ammonia and oxygen gas in ostwald process. Potassium nitrate and sulfuric gas can be used to produce nitric gas in laboratory scale. Nitric acid is used to manufacture explosives, some metal nitrates and many more.

nitric molecule structure

Figure : Nitric molecule



In this tutorial we discuss following sections of nitric acid. Click on a section what you want to study. Click on what you want to learn about HNO3.

  1. Characteristics of nitric acid
  2. Prepare nitric acid in laboratory
  3. Nitric acid industrially manufacturing - ostwald method
  4. Reactions of nitric acid

Characteristics of nitric acid

  • A strong acid
  • A strong oxidizing agent
  • Decomposes when exposes to the sunlight


Prepare nitric acid laboratory

The reaction of potassium nitrate and concentrated sulfuric acid can be used to prepare nitric acid in the laboratory. When mixture is heated, formed nitric acid can be separated by distillation process.

conc sulfuric and potassium nitrate prepare nitric acid


Decomposition of nitric acid

When nitric acid is heated or exposed to the sun light it turns yellow owing to it's decomposition . The yellow colour observed in bottles of nitric acid is due to the formation of nitrogen dioxide(NO2).

Decomposition-of-nitric-acid

Raw materials of nitric Acid manufacturing process industrially



Nitric acid manufacturing process - ostwald method


step 1

Prepare nitric oxide - NO

  • NH3 and O2 are mixed to 1:9 volume ratio.
  • The mixture is heated upto 850 - 10000C temperature. That mixture send through Pt/Rh catalyst. Then exothermic reactions happens and produces NO and H2O . Due to exothermic reaction reaction happens easily after it was started.
  • 4NH3(g) + 5O2(g) → 4NO + 6H2O(g) + ΔH
  • ΔH0 = -904kJmol-1
  • Reaction happens under high pressure. For higher pressure more reactants has to be entered. That increases more impacts between reactants and catalysts. This increases reaction rate.
  • Excess air will confirm completeness of ammonia oxidization.

step 2

Prepare nitrogen dioxide (NO2)

  • Next reaction give us NO2(g). This reaction should be done at low temperature than previous reaction.(<1500C). Hence NO is cooled and cold air mixed with NO. NO reacts with excess O2
  • NO(g) + O2(g) → NO2(g) + ΔH
  • ΔH0 = -115kJmol-1

step 3

Prepare nitric acid

  • NO2(g) is cooled before it sends to the water.
  • NO2(g) is absorbed very well in the water and produce HNO3 . (oxidizing)
  • 3NO2(g) + H2O2(l) → 2HNO3(aq) + 4NO(g)
  • Released nitric oxide (NO) in step 3 is recycled to the step 2

Requirements for 96% translation in industrial nitric acid manufacturing

  • Pressure: 4-10 atm
  • Temperature: 850- 10000C
  • Pt catalyst(10% Rh content)
Nitric acid production process

Uses of nitric acid

  • To produce TNT, TNG explosives.
  • Important chemical
  • Get dissolved metals
  • to produce fertilizers
  • to produce metal nitrates:
    • AgNO3: photographic films and paper
    • KNO3: Gun powder
    • NaNO3: preservation for meat, manufacture of sausages


Environmental pollution due to nitric acid manufacturing industry

As other chemical industries in the world, nitric acid production causes to environmental pollution.

  • By Ammonia gas, atmosphere is polluted.
  • Inhaling Ammonia cause to health problems
  • Water is used to reduce temperature of the system. When that water is released to the environment there may be effects to animals and plants.
  • NO & NO2 cause to acid rains, damages to Ozone layer, photochemical smog.


Decomposition of nitrous acid

At low temperature, slow decomposition of nitrous acid gives nitric acid and nitric oxide(NO)

Decomposition of nitrous acid


Nitric acid reactions

Nitric acid is both a strong acid and a strong oxidizing agent, nitric acid can dissolve most metals.


Dehydration of nitric acid

Dinitrogen pentoxide, N2O4 , is the anhydride of nitric acid, from which it can be prepared by dehydration of nitric acid at low temperatures,

Dehydration of nitric acid

Sulfur and hot concentrated nitric acid reaction

Sulfur is oxidized into sulfuric acid(H2SO4) and nitric acid will be reduced to nitrogen dioxide(NO2). This reaction is an example to oxidizing ability of nitric acid.

Sulfur and Nitric acid reaction

Sulfides and nitric acid

Sulfides are oxidized to sulfates by concentrated nitric acid. Nitric acid is reduced in to nitric oxide(NO).



Zinc sulfide and nitric acid reaction

Zinc sulfide and nitric acid reaction

Aqua regia

The mixture containing one volume of concentrated nitric and three volumes of concentrated hydrochloric is known as aqua regia , and it will dissolve even gold and platinum.


Copper and nitric acid

According to the concentration of nitric acid, different products are given. If dilute nitric is used, nitric oxide (NO) is given. With concentrated nitric acid, nitrogen dioxide (NO2) is given. Copper is oxidized into copper(II) with both dilute or concentrated nitric acid and blue colour solution will be given in both occasions.

Cu + dilute HNO3

Cu + dilute HNO3

Cu + concentrated HNO3

Cu + conc HNO3

Tin and nitric acid reaction

Tin(Sn) and dilute nitric acid react to form Sn(NO3)2, NH4NO3 and water.

Sn and nitric acid reaction


Lead and nitric acid reaction

Lead(Pb) and dilute nitric acid react to form Pb(NO3)2, NO2 and water.

Pb and nitric acid reaction


Nitric acid and sulfuric acid

In the reaction of sulfuric acid with nitric acid, the nitronium ion(NO2 + ) is generated. H2SO4 + HNO3


Hot concentrated nitric acid and carbon reaction

Carbon(C) and hot concentrated HNO3 acid react to give CO2, NO2, H2O.

Hot concentrated nitric acid and carbon reaction

Hot concentrated nitric acid and sulfur reaction

Sulfur(S) and hot concentrated HNO3 acid react to give H2SO4, NO2, H2O.

Hot concentrated nitric acid and sulfur reaction

Nitric acid and phosphorus reaction

Phosphorus(P) and HNO3 acid react to give H3PO4, NO2, H2O.

Nitric acid and phosphorus reaction

Nitric acid and silver metal reaction

Ag react with HNO3 acid to give AgNO3, NO2 and H2O.

Nitric acid and silver metal reaction

Nitric acid and hydrogen sulfide(H2S) rection

S and NO are given as the products by the reaction of H2S and HNO3.

Nitric acid and hydrogen sulfide reaction

Questions of Nitric acid manufacturing

Ask your question

What are the raw materials required for the manufacture of nitric acid by ostwald process

Ammonia, oxygen, water are the raw materials of nitric acid manufacturing. Ammonia can be obtained by haber process. Ammonia gas is oxidized to nitrogen dioxide by oxygen. Nitrogen dioxide is dissolved in water.



What are the nitric acid production methods

  • Potassium nitrate reacts with concentrated nitric acid on heating to give nitric acid. Nitric acid is separated by distillaation. This method can be used in laboratory.
  • Using ammonia and oxygen, nitroc acid can be prepared. This is the industrial method, ostwald process.

What are the catalyst used in large scale preparation of nitric acid?

In ammonia oxiddation to NO, Pt is used as the catalyst.