Lead(II,IV) oxide

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Lead tetroxide
)
Lead(II,IV) oxide
Sample of pulverised lead(III,IV) oxide
Names
Preferred IUPAC name
Lead tetroxide [1]
Other names
Minium, red lead, triplumbic tetroxide
Identifiers
3D model (
JSmol
)
ChemSpider
ECHA InfoCard
 100.013.851 Edit this at Wikidata
EC Number
  • 215-235-6
UNII
UN number 1479
  • InChI=1S/4O.3Pb checkY
    Key: XMFOQHDPRMAJNU-UHFFFAOYSA-N checkY
  • O1[Pb]O[Pb]11O[Pb]O1
Properties
Pb3O4
Molar mass 685.6 g·mol−1
Appearance Vivid orange crystals
Density 8.3 g/cm3
Melting point 500 °C (decomposition)
Vapor pressure 1.3 kPa (at 0 °C)
Structure
Tetragonal, tP28
P42/mbc, No. 135
Hazards
GHS labelling:
GHS07: Exclamation mark GHS08: Health hazard GHS09: Environmental hazard
Danger
H272, H302, H332, H360, H373, H410
P201, P220, P273, P308+P313, P501
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
3
0
0
Related compounds
Related lead oxides
 Lead(II) oxide
Lead(IV) oxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkY☒N ?)

Lead(II,IV) oxide, also called red lead or

Pb(II) and Pb(IV) in the ratio of two to one.[2]

Structure

Lead(II,IV) oxide is lead(II) orthoplumbate(IV) [Pb2+]2[PbO4−4].

orthorhombic (Pearson symbol oP28, 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]

  • 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 (PbO; also called litharge) in air at about 450–480 °C:[5]

6 PbO + O2 → 2 Pb3O4

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

PbO + KOH + H2O → K[Pb(OH)3]

Another method of preparation relies on

annealing of lead(II) 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(II,IV) oxide can be prepared by reaction of potassium

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

mine fire.[6]

Reactions

Red lead is virtually insoluble in water and in

glacial acetic acid and a diluted mixture of nitric acid and hydrogen peroxide
.

When heated to 500 °C, it decomposes to lead(II) oxide and oxygen. At 580 °C, the reaction is complete.

2 Pb3O4 → 6 PbO + O2

lead(IV) oxide
:

Pb3O4 + 4 HNO3 → PbO2 + 2 Pb(NO3)2 + 2 H2O

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.

Use

Red lead has been used as a

pyrotechnic stars
.

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.

Red lead was used for engineer's scraping, before being supplanted by engineer's blue.

It is also used as an adulterating agent in turmeric powder.

Physiological effects

Main article: Lead poisoning

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.

Lead(II,IV) oxide was shown to be

laboratory animals
. Its carcinogenicity for humans was not proven.

Minium from a mine fire at Broken Hill, Australia

History

This compound's

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]

As a finely divided powder, it was also sprinkled on

Lichtenberg figures
.

In

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]

See also

References

  1. ^ "VOLUNTARY RISK ASSESSMENT REPORT ON LEAD AND SOME INORGANIC LEAD COMPOUNDS". Retrieved 2012-12-25.
  2. ISBN 978-0-08-037941-8
    .
  3. ISBN 0-12-352651-5
    .
  4. doi:10.1016/0022-4596(78)90081-6
    .
  5. ISBN 978-3527306732
    .
  6. ^ Minium
  7. ^ James Balfour Paul, Accounts of the Treasurer of Scotland, vol. 2 (Edinburgh, 1900), p. 277.
  8. S2CID 37730169
    .
  9. ^ "The London Lancet: A Journal of British and Foreign Medicine, Physiology, Surgery, Chemistry, Criticism, Literature and News". 1853.

External links

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