General properties of Nitric Acid
- Nitric acid is a strong corrosive acid at ambient temperature and strong oxidizing agent.
- Nitric acid is commercially available in an azetrope composition with the water molecule.
- Nitric acid is colorless and tends to acquire a yellow color due to decomposition into oxides of nitrogen and water.
- Pure form of nitric acid is not stable and even at ordinary temperature it undergoes slight decomposition.
Production of Nitric Acid
- Ostwald process
- Laboratory synthesis
Ostwald process is a chemical process for commercial nitric acid preparation and it is developed by the Wihelm Ostwald in 1902. The Ostwald process is one of the most important process and it provides raw material for the fertilizer industry. Ammonia (NH3) is used as a raw material for the production of Nitric acid in Ostwald process and it’s obtained from the Haber’s process. Catalyst such as Platiunum combined with 10% Rhodium is used in the Ostwald process.
4 NH3 (g) + 5 O2 (g) → 4 NO (g) + 6 H2O (g)
2 NO (g) + O2 (g) → 2 NO2 (g)
3 NO2 (g) + H2O (l) → 2 HNO3 (aq) + NO (g)
Aqueous HNO3 obtained from the Ostwald process can be concentrated by distillation up to 68% and further concentration to 98% can be achieved by dehydration with concentrated H2SO4.
Nitric acid is made by laboratory synthesis by thermal decomposition of cupric nitrate producing nitrogen oxide and oxygen. Nitrogen oxide gases, which then passed through the water to produce nitric acid and byproduct as sodium sulphate.
2 Cu(NO3)2 → 2 CuO (s) + 4 NO2 (g) + O2 (g)
4 NO2 (g) + O2 (g) + 2 H2O (l) → 4 HNO3 (aq)
Nitric acid is also alternatively produced by the sodium nitrate salt with highly concentrated sulphuric acid. High purity, red fuming Nitric acid is obtained from distilling this mixture around 830C. The distillate red fuming nitric acid is then converted to the white fuming nitric acid.
2 NaNO3 + H2SO4 → 2 HNO3 + Na2SO4
- Fertilizer Industry
- Chemical Reagent
- Chemical Industry
- Cleaning agent
- Aerospace Industry
- Other Applications
Nitric acid is extensively used by percentage of 80% in fertilizer industries. Nitric acid is the key chemical for the preparation of nitrogen fertilizers such as Ammonium nitrate and calcium nitrate.
Nitric acid is used as an excellent analytical chemical reagent for determining metal traces in solutions. It is used in atomic absorption spectroscopy for the digestion of the sample. It is also used a precursor to organic nitrogen compounds such as nylon and adipic acid. It is also used widely in the calorimetric test in order to determine the difference between heroin and morphine.
Nitric acid is used in explosive manufacture of various products such Trinitrotoluene (TNT), RDX, gun cotton, Ammonal, nitrocellulose and nitroglycerine. In chemical industries, Nitric acid is extensively used in the preparation of nitrate salts such as calcium nitrate, silver nitrate and ammonium nitrate.
Combination solution of Nitric acid, water and alcohol is called as Nital and it’s extensively used as an etchant and cleaning agent.
In the field of aerospace engineering, nitric acid is widely used as an oxidizer in liquid-fuel rockets.
Nitric acid is used as a laboratory reagent and used in purification of silver, gold and platinum. Nitric acid is one of the integral components for the preparation of Aqua Regia which dissolves most of noble metals.In electrochemical industry, Nitric acid is used as a chemical doping agent for organic semiconductors and in purification processes for raw carbon nanotubes. Lower concentration of nitric acid is used in the woodworking industry for ageing pine and maple woodworks.Aqueous blends of nitric acid and phosphoric acid is used in the food and dairy industry to remove precipitated calcium and magnesium compounds.Nitric acid can also be used as a spot test for alkaloids like LSD.
|Color in a liquid state||Transparent to yellow|
|Color in a gaseous state||Transparent to yellow or brown|
|Odour||Sweet to pungent|
|In liquid state||Rapidly attacks flesh and most organic matter|
|As gaseous oxides||Anaesthetic to dangerously toxic|
|Molar mass||63.01 g / mol|
|Density||1.5192 g / cm3|
|Freezing point||< 0oF|
|Boiling Point of constant – (68% HNO3 at 78mmHg)||120.5°C|
|Heat capacity at 27°C||26.24 cal /g mol|
|Heat of fusion||2503 cal / g mol|
|Heat of vaporisation at 20°C||9426 cal / g mol|