Salts of nitric acid are called nitrates which are obtained by the action of nitric acid on metals or their oxides or carbonates. They are usually soluble in water.
Take 2-3 drops of HN03 in a test tube, dilute it. Take about 1 mL of this dil. solution of HN03 and about double volume of conc. H2S04 to it. Cool the mixture in cold water then add freshly prepared FeS04 solution slowly into the test tube of mixture maintained in inclined position. Brown ring is formed at the surface of the contact of the liquids.
Nitric acid oxidises FeS04 in presence of H2S04 into Fe2(SO4)3 and is itself reduced to NO. This NO dissolves in excess of FeS04 solution giving the brown coloured ring of FeS04.NO; Nitrosoferrous sulphate.
Ring test for nitrate.
This test can be carried out for any nitrate salt also.