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This test differentiates N0₃- ion from N0₂- ion, sińce the latter gives the brown ring in presence of dii. H₂S0₄ or even acetic acid, while N0₃ ion dose not form the ring except in presence of conc. H₂S0₄.

(N0₂, I and Br ions will interfere)

III. Special Tests

1- For Nitrate:

Ammonia test:

If solution of NOj- is boiled with Zn⁰ or Al⁰ metals and NaOH solution, NH₃ will be evolved which can identified by its odor or with red litmus

paper (nitrites interfere).

N0₃ + 4Zn°+ 7 OH 3NH₃ + 4[Zn0₂]² + 2H₂0

zincate ions

3N0₃ + 8AI°+ 50H + 2H₂0    3NH₃ + 8 [AI0₂]

In acidic solution ( CH₃COOH), nitrate can be reduced with Zn⁰ to nitrite.