Download Nitrites Potassium nitrate decomposes to the nitrite when heated to

Nitrites
Potassium nitrate decomposes to the nitrite when heated to its melting point. Reducing
agents can also be added to facilitate the reaction to completion these are Pb, Fe 2S, Fe2O, Cu,
MnO2, Fe, chromic, and sulfur. Best results were from MnO2 at 650 ⁰C.
The nitrite can also be formed by reduction of a nitrate with a metal in their aqueous
solutions. Examples of the reducing agents are Zn, K, Na, Pb, or Zn-Amalgam. The problem with
these reactions is the nitrite when heated in the aqueous solution will absorb oxygen from the
air and water, which reforms the nitrate. The electrolysis of sodium nitrate with amalgated
copper cathode. Silver nitrate solution reacted with silver and heated yields silver nitrite.
Ammonia can be oxidized to ammonium nitrite by the addition of hydrogen peroxide or
potassium permanganate.
In the reaction of a nitrate with granulated lead, the reducer should be in 15% excess.
The reaction commences at the boiling point and after 2 hours at 420 ⁰C, complete reduction is
obtained (example with sodium nitrate).
KNO3 + H3PO3 → KNO2 + H3PO4
NaNO3 + CaO + SO2 → CaSO4 + NaNO3
2KNO3 → 2KNO2 + O2 with heat
NaNO3 + R → NaNO2 + RO where R is the metal reducing agent mentioned above
Pb + NaNO3 → PbO + NaNO2
3Pb + 4NaNO3 → Pb3O4 + 4NaNO2