Nitrate test

[1] A common nitrate test, known as the brown ring test[2] 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.

This reaction has been used to test for organic nitrates as well,[7] and has found use in gunshot residue kits detecting nitroglycerine and nitrocellulose.

[8] The nitrate ion can easily be identified by heating copper turnings along with concentrated sulfuric acid.

Effervescence of a brown, pungent gas is observed which turns moist blue litmus paper red.