Nitrates

1. By neutralizing nitric acid with an alkali or base
2. By the action of nitric acid on a carbonate
3. By the action of a metal on nitric acid (only for magnesium, zinc, lead, and copper)

1. All nitrates are soluble and form crystalline solids
2. Action of heat on nitrates

a) Sodium and potassium nitrates give nitrites

b) Many metal nitrates give the oxide

Example:

i. Effect of heat on copper nitrate crystals. When the blue crystals of copper nitrate are heated in a boiling tube, they dissolve in their water of crystallization. Prolonged heating gives brown fumes of nitrogen dioxide and a black residue of copper oxide.

ii. Effect of heat on lead nitrate crystals. When heated, they decrepitate (expand with a crackling noise) and melt. Prolonged heating gives brown fumes of nitrogen dioxide and a yellow residue of lead monoxide (litharge).

c) Silver and mercury nitrates give the metal

d) Ammonium nitrates give nitrous oxide

3. The action of concentrated sulphuric acid

Concentrated sulphuric acid, when heated with a nitrate, liberates nitric acid.

4. All nitrates except those of sodium and potassium are hydrated. Sodium nitrate and calcium nitrate are deliquescent, and other nitrates are not.

Summary of chemical properties of Nitrates

1. Add concentrated sulphuric acid to the solid nitrate and warm. Acid fumes (nitric acid) are evolved. Add 3–4 copper turnings and warm the mixture. The colour of the gas turns deep brown.
2. The brown ring test is normally used to confirm nitrates.

To a solution of nitrate, add a few drops of freshly prepared ferrous sulphate solution. A few drops of concentrated sulphuric acid are added carefully and a brown ring is obtained at the junction between the liquids. It is nitrate ferrous sulphate (FeSO4NO) that is formed.

The nitrogen monoxide then reacts with more iron(II) sulphate to give the brown compound, which appears as a brown ring.

1. Potassium nitrate is used as a food preservative; it is also used to make slow-burning fuses.
2. Sodium nitrate is mainly used as a fertilizer.
3. Ammonium nitrate is mixed with chalk; the mixture is known as NITROCHALK, widely used as a fertilizer.
4. It is also used in manufacturing explosives.
5. Silver nitrate is used to make silver bromide and silver iodide, chemicals used to make photographic film.