Nitric Acid Properties and Uses

Nitric acid is an oxidising mineral acid with physical and chemical properties that make it one of the most useful inorganic minerals. Nitric acid is used in a wide range of industries the most common of which are the production of explosives, nitrogen fertilisers and dyestuffs.

Originally Nitric acid was produced via several routes, but in 1906 the first large scale production of Nitric acid using the Ostwald process came on stream and since then almost all nitric acid is manufactured by this route. The Ostwald process takes place in 3 main steps, the initial step being the oxidation of ammonia to produce nitrogen monoxide, the second the oxidation of the nitrogen monoxide to produce nitrogen dioxide or tetraoxide and finally the absorption of the nitrogen oxides in water to produce nitric acid.

Properties of Nitric Acid:

Molecular Weight 63.02
Color In liquid state: transparent to yellow
As gaseous oxides: transparent yellow or brown
Odour Sweet to pungent
Hazards In liquid state: Rapidly attacks flesh and most organic matter
As gaseous oxides: anaesthetic to dangerously toxic
Melting Point -41.6oC
Boiling Point of Constant (68% HNO3 at 78mmHg) 120.5oC
Density (68% HNO3 at 20oC) 1.41g/l
Heat Capacity at 20oC 26.24 cal /g mol
Heat of Fusion 2503 cal /g mol
Heat Vaporisation at 20oC 9426 cal /g mol

Table extracted from -‘Nitric Acid and Fertilizer Nitrates’, fertilizer science and technology series – volume 4, edited by Cornelius Keleti.