Lead(II,IV) oxide is lead(II) orthoplumbate(IV) [Pb2+]2[PbO4−4].[3] It has a tetragonal crystal structure at room temperature, which then transforms to an orthorhombic (Pearson symboloP28, Space group Pbam, No. 55) form at temperature 170 K (−103 °C). This phase transition only changes the symmetry of the crystal and slightly modifies the interatomic distances and angles.[4]
In solution, lead(II,IV) oxide can be prepared by reaction of potassium plumbate with lead(II) acetate, yielding yellow insoluble lead(II,IV) oxide monohydratePb3O4·H2O, which can be turned into the anhydrous form by gentle heating:
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.[6]
With iron oxides and with elemental iron, lead(II,IV) oxide forms insoluble iron(II) and iron(III) plumbates, which is the basis of the anticorrosive properties of lead-based paints applied to iron objects.
Red lead is used as a curing agent in some polychloroprene rubber compounds. It is used in place of magnesium oxide to provide better water resistance properties.
When inhaled, lead(II,IV) oxide irritates the lungs. In case of high dose, the victim experiences a metallic taste, chest pain, and abdominal pain. When ingested, it is dissolved in the gastric acid and absorbed, leading to lead poisoning. High concentrations can be absorbed through skin as well, and it is important to follow safety precautions when working with lead-based paint.
Long-term contact with lead(II,IV) oxide may lead to accumulation of lead compounds in organisms, with development of symptoms of acute lead poisoning. Chronic poisoning displays as agitation, irritability, vision disorders, hypertension, and a grayish facial hue.
This compound's Latin name minium originates from the Minius, a river in northwest Iberia where it was first mined.
Lead(II,IV) oxide was used as a red pigment in ancient Rome, where it was prepared by calcination of white lead. In the ancient and medieval periods it was used as a pigment in the production of illuminated manuscripts, and gave its name to the minium or miniature, a style of picture painted with the colour.
Made into a paint with linseed oil, red lead was used as a durable paint to protect exterior ironwork. In 1504 the portcullis at Stirling Castle in Scotland was painted with red lead, as were cannons including Mons Meg.[7]
In traditional Chinese medicine, red lead is used to treat ringworms and ulcerations, though the practice is limited due to its toxicity. Also, azarcón, a Mexican folk remedy for gastrointestinal disorders, contains up to 95% lead(II,IV) oxide.[8]
It was also used before the 18th century as medicine.[9]
^Egon Wiberg; Nils Wiberg; Arnold Frederick Holleman (2001). Inorganic chemistry. Academic Press. p. 920. ISBN0-12-352651-5.
^Gavarri, J; Weigel, Dominique; Hewat, A. W. (1978). "Oxydes de plomb. IV. Évolution structurale de l'oxyde Pb3O4 entre 240 et 5 K et mécanisme de la transition" [Lead oxides. IV. Structural evolution of the oxide Pb3O4 between 240 and 5 K and mechanism of transition]. Journal of Solid State Chemistry. 23 (3–4): 327. Bibcode:1978JSSCh..23..327G. doi:10.1016/0022-4596(78)90081-6.
^James Balfour Paul, Accounts of the Treasurer of Scotland, vol. 2 (Edinburgh, 1900), p. 277.
^Bose, A.; Vashistha, K; O'Loughlin, B. J. (1983). "Azarcón por empacho – another cause of lead toxicity". Pediatrics. 72: 108–118. doi:10.1542/peds.72.1.106. S2CID37730169.
