Preparation
Lead tetroxide is prepared by calcination of lead(II) oxide (also called litharge) in air at about 450 to 480 °C:
- 6 PbO + O2 → 2 Pb3O4
The resulting material is contaminated with lead(II) oxide. If a pure compound is desired, PbO can be removed by a potassium hydroxide solution:
- PbO + KOH + H2O → K (aq)
Another method of preparation relies on annealing of lead carbonate (cerussite) in air:
- 6 PbCO3 + O2 → 2 Pb3O4 + 6 CO2
Yet another method is oxidative annealing of white lead:
- 3 Pb2CO3(OH)2 + O2 → 2 Pb3O4 + 3 CO2 + 3 H2O
In solution, lead tetroxide can be prepared e.g. by reaction of potassium plumbate with lead acetate, yielding yellow insoluble lead tetroxide monohydrate, Pb3O4·H2O, which can be turned into the anhydrous form by gentle heating:
- K2PbO3 + 2 Pb(OCOCH3)2 + H2O → Pb3O4 + 2 KOCOCH3 + 2 CH3COOH
Natural minium is uncommon, forming only in extreme oxidizing conditions of lead ore bodies. The best known natural specimens come from Broken Hill, New South Wales, Australia, where they formed as the result of a mine fire.
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