Brown Ring Test － Test for Nitates

NO₃^- + H₂SO₄ →HNO₃ + HSO₄^2-
HNO₃ + 3Fe²⁺ →NO+ 3Fe³⁺+ 2H₂O
Fe²⁺+ NO → [Fe(NO)]²⁺ (brownish nitroso complex)/
[Fe(H₂O)₆]²⁺ + NO → [Fe(H₂O)₅(NO) ]²⁺ + H₂O