Lead Plumbate

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Lead plumbate, also called red lead, minium or Mennige (in German), is a mineral showing colors from light red to brown/yellow tints. As a pure chemical it shows a vivid red. Minium is rare and occurs in lead mineral deposits that have been subjected to severe oxidizing conditions. It also occurs as a result of mine fires. It is most often associated with galena, cerussite, massicot, litharge, native lead, wulfenite and mimetite.

Lead plumbate is obtained by heating lead monoxide (\(PbO\)) to 450-480°C in air:

\[3 PbO + 1/2 O_2 \rightarrow Pb_3O_4 \nonumber \]

or by oxidative annealing of lead white:

\[3 Pb_2CO_3(OH)_2 + O_2 \rightarrow 2 Pb_3O_4 + 3 CO_2 + 3 H_2O \nonumber \]

Lead plumbate decomposes into lead monoxide and oxygen above 550°C.

\(Pb_3O_4\) can be seen formally as a lead(II)plumbate(IV), \(Pb_2[PbO_4]\), or \(2PbO\cdot PbO_2\). In nitric acid, the lead(II) oxide reacts forming lead nitrate, while the insoluble lead(IV) oxide is left unchanged:

\[Pb_3O_4 + 4 HNO_3 \rightarrow 2 Pb(NO_3)_2 + PbO_2 + 2 H_2O \nonumber \]

Lead plumbate is virtually insoluble in water. However, it dissolves in hydrochloric acid (which is present in the stomach), and is therefore toxic when ingested. Lead plumbate (in a mixture with linseed oil or other organic adhesives) has been used as an anti-corrosion paint for iron. It forms insoluble iron(II) and iron(III) plumbates when brought into contact with iron oxides and with elementary iron. However, its use as a protective undercoat paint is limited due to its toxicity.

Lead plumbate was used as a red pigment in ancient and medieval periods for paintings and the production of illuminated manuscripts (the term miniature is connected to the name of the substance).

Contributors and Attributions

Hans Lohninger (Epina eBook Team)