Nitrogen combines with O₂ under different conditions to form a number of binary oxides which differ with respect to the oxidation state of the nitrogen atom. The important oxides are N₂O, NO, N₂O₃, NO₂, N₂O₄ and N₂O₅. N₂O and NO both are neutral. Nitrous oxide ( N₂O) has a sweet taste and its main use is as anesthetic. When inhaled in mild quantities it causes hysterical laughter so it is also called Laughing gas. Nitric oxide (NO) can be obtained by treating a mixture of sodium nitrite and ferrous sulfate with dil. H₂SO₄ . N₂O₅ is the strongest oxidizing agent.