<P> Ring Test is a confirmatory test for HNO3 as well as nitrate radical . </P> <P> A common nitrate test, known as the brown ring test can be performed by adding iron (II) sulfate to a solution of a nitrate, then slowly adding concentrated sulfuric acid such that the acid forms a layer below the aqueous solution . A brown ring will form at the junction of the two layers, indicating the presence of the nitrate ion . Note that the presence of nitrite ions will interfere with this test . </P> <P> The overall reaction is the reduction of the nitrate ion by iron (II) which is oxidised to iron (III) and formation of a nitrosonium complex where nitric oxide is reduced to NO . </P> <Dl> <Dd> 2HNO + 3H SO + 6FeSO--->> 3Fe (SO) + 2NO + 4H O </Dd> <Dd> (Fe (H O)) SO + NO = (Fe (H O) (NO)) SO + H O </Dd> </Dl>

Solid iron reacts with aqueous copper (ii) nitrate