Lead(II,IV) oxide: Difference between revisions

{{chembox

| verifiedrevid = 429509813

| ImageSize = 250px

| ImageName = Red lead powder

| IUPACName = lead(II,IV) oxide

| OtherNames =

| Section1 = {{Chembox Identifiers

| StdInChI_Ref = {{stdinchicite|correct|chemspider}}

| StdInChI = 1S/4O.3Pb

| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}

| StdInChIKey = XMFOQHDPRMAJNU-UHFFFAOYSA-N

| CASNo_Ref = {{cascite|correct|CAS}}

| ChemSpiderID=21169908

| PubChem =

| SMILES = O1[Pb]O[Pb]12O[Pb]O2

| Section2 = {{Chembox Properties

| Formula = Pb₃O₄<br/>

2PbO·PbO₂

| MolarMass = 685.598 g/mol

| Appearance = orange red powder

| Density = 8.3 g/cm³

| MeltingPt = 500°C

| BoilingPt =

| Solubility = insoluble

| Solubleother = slightly soluble in [[hydrochloric acid]]

| Section3 = {{Chembox Structure

| CrystalStruct = [[Tetragonal]], [[Pearson symbol|tP28]]

| SpaceGroup = P4₂/mbc, No. 135

}}

| Section7 = {{Chembox Hazards

| MainHazards = toxic from lead presence

| FlashPt = none

| Autoignition = none

'''Lead tetroxide''', also called '''minium''', '''red lead''' or '''triplumbic tetroxide''', is a bright red or orange [[crystalline]] or [[amorphous]] [[pigment]]. Chemically, red lead is lead [[oxide|tetroxide]], Pb₃O₄, or 2PbO·PbO₂.

This compound's [[Latin]] name ''minium'' originates from the [[Minius River]] in northwest [[Spain]] where it was first mined. [[Minium (mineral)|Natural minium]] is uncommon, forming only in extreme oxidizing conditions of [[lead]] ore bodies. The best specimens known come from [[Broken Hill]], [[New South Wales]], [[Australia]], where they formed as the result of a mine fire.<ref>[http://www.galleries.com/minerals/oxides/minium/minium.htm Minium]</ref>

Lead tetroxide is used in the manufacture of [[Lead–acid_battery|batteries]], [[lead glass]] and [[rust]]-proof [[primer (paint)|primer paints]].

Lead tetroxide 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.<ref>{{cite journal|doi=10.1016/0022-4596(78)90081-6|title=Oxydes de plomb. IV. Evolution structurale de l'oxyde Pb3O4 entre 240 et 5°K et mécanisme de la transition|year=1978|author=Gavarri, J|journal=Journal of Solid State Chemistry|volume=23|pages=327}}</ref>

Image:Red-lead-unit-cell-3D-balls.png|[[Crystal structure#Unit cell|Unit cell]] of tetragonal Pb₃O₄

Image:Red-lead-3D-balls.png|Part of tetragonal red lead's crystal structure

== 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[Pb(OH)₃] (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

Red lead is virtually insoluble in water and in alcohol. However, it is soluble in [[hydrochloric acid]] present in the [[stomach]], and is therefore [[toxic]] when ingested. It also dissolves 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

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

With iron oxides and with elemental [[iron]], lead tetroxide forms insoluble iron(II) and iron(III) [[plumbate]]s, which is the basis of the anti-[[corrosion|corrosive]] properties of lead-based paints applied to iron objects.

== Use ==

Lead tetraoxide is most often used as a [[pigment]] for [[Primer (paint)|primer]] [[paint]]s for [[iron]] objects. Due to its [[toxicity]], its use is being limited. In the past, it was used in combination with [[linseed oil]] as a thick, long-lasting anti-corrosive paint. The combination of minium and linen fibres was also used for [[plumbing]], now replaced with [[PTFE]] tape. Currently it is mostly used for manufacture of [[glass]], especially [[lead glass]]. It finds limited use in some amateur [[pyrotechnics]] as a relatively potent [[oxidizer]].

Red lead was also used for engineer's [[Hand scraper|scraping]], before being supplanted by [[Engineer's blue]]. In [[traditional Chinese medicine]], red lead is used to treat [[ringworms]] and [[ulceration]]s, though the practice is limited due to its toxicity.

== Physiological effects ==

{{main|Lead poisoning}}

When inhaled, lead tetroxide irritates 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 tetroxide 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 also a grayish facial hue.

Lead tetroxide was shown to be [[carcinogenic]] for laboratory animals. Its carcinogenicity for humans was not proven.

[[Image:Minium- BYU.jpg|thumb|left|'''Minium''' from a mine fire at [[Broken Hill]], [[Australia]] ]]

Lead tetroxide 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 manuscript]]s, and gave its name to the ''minium'' or [[miniature (illuminated manuscript)|miniature]], a style of picture painted with the colour. As a finely divided powder, it was also sprinkled on [[dielectric]] surfaces to study [[Lichtenberg figures]].

* [[Lead(II) oxide]], PbO

* [[Lead dioxide]] (Lead(IV) oxide), PbO₂

{{reflist}}

* [http://www.npi.gov.au/database/substance-info/profiles/50.html National Pollutant Inventory - Lead and Lead Compounds Fact Sheet]

* [http://webmineral.com/data/Minium.shtml Minium mineral data]

[[Category:Oxides]]

[[Category:Lead compounds]]

[[Category:Lead minerals]]

[[Category:Oxide minerals]]

[[Category:Corrosion inhibitors]]

[[ar:رابع أكسيد الرصاص]]

[[bg:Миниум]]

[[ca:Mini]]

[[cs:Oxid olovnato-olovičitý]]

[[da:Mønje]]

[[de:Blei(II,IV)-oxid]]

[[es:Tetróxido de plomo]]

[[fr:Minium]]

[[ko:광명단]]

[[io:Miniumo]]

[[it:Minio]]

[[nl:Loodtetraoxide]]

[[ja:鉛丹]]

[[no:Mønje]]

[[pl:Minia ołowiowa]]

[[pt:Tetróxido de chumbo]]

[[ru:Сурик (свинцовый)]]

[[fi:Mönjä]]

[[sv:Blymönja]]

[[zh:四氧化三鉛]]