Lead(II,IV) oxide

Lead(II,IV) oxide, also called minium, red lead or triplumbic tetroxide, is a bright red or orange crystalline or amorphous pigment. Chemically, red lead is Pb₃O₄, or 2 PbO·PbO₂. Pb₃O₄,is [2PbO].[PbO₂] or Lead(II,IV) oxide. It is used in the manufacture of batteries, lead glass and rust-proof primer paints.

Structure

Lead(II,IV) oxide has a tetragonal crystal structure at room temperature, which transforms to an orthorhombic (Pearson symbol oP28, Space group = Pbam, No 55) form at temperature 170 K. This phase transition only changes the symmetry of the crystal and slightly modifies the interatomic distances and angles.

Unit cell of tetragonal Pb₃O₄ (Key:      Pb      O)

Unit cell of tetragonal Pb₃O₄ (Key:      Pb      O)

Part of tetragonal red lead's crystal structure

Part of tetragonal red lead's crystal structure

Preparation

Lead(II,IV) oxide is prepared by calcination of lead(II) oxide (also called litharge) in air at about 450 to 480 °C:

The resulting material is contaminated with lead(II) oxide. If a pure compound is desired, PbO can be removed by a potassium hydroxide solution: