The Nitrate ion

Nitrate ions are very good oxydators, but only under the condition that sufficient acid (H+) is present.
The nitrate has various ways to react, dependent on the concentration of that nitrate:
  1. High concentrations

    NO3-+ 2H+ + 1 e- NO2 + H2O

  2. Moderate and low concentrations

    1. With few acid: NO3-+ 4H+ + 3 e- NO + 2H2O
    2. With more acid: 2NO3-+ 12H+ + 10 e- N2 + 6H2O

  3. Very low concentrations

    2NO3-+ 10H+ + 8 e- N2O + 5H2
N2 is the normal Nitrogen gas, colourless and odourless.
NO  + NO2 the 'nitrous vapors', yellow brown, suffocating
N2O a colourless gas, in fact a kind of nerve affecting gas.
It causes strange face contractions (kind of laughing) and it helps to anaestesise people (or animals).
It was found in 1860 and applied, for example, by dentists.