A positive brown ring test indicates the presence of
Answer Details
The positive brown ring test indicates the presence of nitrate ions (NO3). The test is done by adding freshly prepared iron(II) sulfate (FeSO4) solution and concentrated sulfuric acid (H2SO4) to the test solution. If nitrate ions are present in the solution, a brown ring will form at the junction of the two liquids. This occurs because nitrate ions reduce Fe2+ ions to Fe3+ ions, which then react with the sulfuric acid to form Fe(HSO4)2 which appears as the brown ring.