The brown ring test is a typical nitrate test that involves adding iron(II) sulphate to a nitrate solution, then slowly adding strong sulfuric acid until the acid forms a layer below the aqueous solution. The existence of the nitrate ion will be shown by the formation of a brown ring at the junction of the two layers. Dark brown ring is formed in the confirmatory test of NO3− − ions. Deep red precipitate with FeCl3 is formed in the presence of CH3COO− ions.