View source for Lead(II) oxide

{{chembox
| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 441024062
| ImageFile1 = Oxid olovnatý.JPG
| ImageSize1 = 244
| ImageFile2 = PbO_structure.png
| ImageSize2 = 180
| IUPACName = Lead(II) oxide
| OtherNames = Lead monoxide<br/>[[Litharge]]<br/>[[Massicot]]<br/>Plumbous oxide
| Section1 = {{Chembox Identifiers
| CASNo = 1317-36-8
| CASNo_Ref = {{cascite|correct|CAS}}
| ChemSpiderID = 140169
| ChEBI = 81045
| EC_number = 215-267-0
| KEGG = C17379
| PubChem = 14827
| UNNumber = 3288 2291 3077
| RTECS = OG1750000
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = 4IN6FN8492
| StdInChI=1S/O.Pb
| StdInChIKey = YEXPOXQUZXUXJW-UHFFFAOYSA-N
| SMILES = O=[Pb]
 }}
| Section2 = {{Chembox Properties
| Formula = PbO
| MolarMass = 223.20 g/mol
| Appearance = red or yellow powder
| Density = 9.53 g/cm<sup>3</sup>
| MeltingPtC = 888
| BoilingPtC = 1477
| Solubility = α-PbO: 0.0504 g/L (25 °C)<br/>β-PbO: 0.1065 g/L (25 °C)<ref name=Greninger1977>{{cite book |author1=Dorothy Greninger |author2=Valerie Kollonitsch |author3=Charles Howard Kline |title=Lead Chemicals |publisher=[[International Lead Zinc Research Organization]] |year=1977 |url=https://books.google.com/books?id=pOQgAQAAIAAJ |page=52}}</ref>
| SolubleOther = insoluble 
| MagSus = {{val|4.20|e=-5|u=cm<sup>3</sup>/mol}}}}
| Section3 = {{Chembox Structure
| Coordination =
| CrystalStruct = [[Tetragonal]], [[Pearson symbol|tP4]]
| SpaceGroup = P4/nmm, No. 129}}
| Section7 = {{Chembox Hazards
| ExternalSDS = [http://www.inchem.org/documents/icsc/icsc/eics0288.htm ICSC 0288]
| GHSPictograms = {{GHS07}}{{GHS08}}{{GHS09}}
| GHSSignalWord = Danger
| HPhrases = {{H-phrases|302|332|351|360Df|362|373|410}}
| PPhrases = {{P-phrases|201|202|260|261|263|264|270|271|273|281|301+312|304+312|304+340|308+313|312|314|330|391|405|501}}
| NFPA-H = 3
| NFPA-F = 0
| NFPA-R = 0
| NFPA-S =
| FlashPt = Non-flammable
| LDLo = 1400&nbsp;mg/kg (dog, oral)<ref name=IDLH>{{IDLH|7439921|Lead compounds (as Pb)}}</ref>}}
| Section8 = {{Chembox Related
| OtherAnions = [[Lead(II) sulfide]]<br/>[[Lead selenide]]<br/>[[Lead telluride]]
| OtherCations = [[Germanium monoxide]]<br/>[[Tin(II) oxide]]
| OtherFunction = [[Lead tetroxide|Lead(II,IV) oxide]]<br/>[[Lead dioxide]]
| OtherFunction_label =
| OtherCompounds = [[Thallium(III) oxide]]<br/>[[Bismuth(III) oxide]]}}}}

'''Lead(II) oxide''', also called '''lead monoxide''', is the [[inorganic compound]] with the molecular formula [[lead|Pb]][[oxide|O]]. It occurs in two [[Polymorphism (materials science)|polymorph]]s: [[litharge]] having a [[tetragonal crystal system|tetragonal crystal structure]], and [[massicot]] having an [[orthorhombic crystal system|orthorhombic crystal structure]]. Modern applications for PbO are mostly in [[lead]]-based industrial [[lead glass|glass]] and industrial ceramics, including computer components.

== Types ==
Lead oxide exists in two [[Polymorphism (materials science)|polymorphs]]:
* Red tetragonal (α-PbO), obtained at temperatures below {{Convert|486|C|F}}
* Yellow orthorhombic (β-PbO), obtained at temperatures above {{Convert|486|C|F}}

==Synthesis==
PbO may be prepared by heating lead metal in air at approximately {{convert|600|C|F|-2}}. At this temperature it is also the end product of decomposition of other [[lead oxide (disambiguation)|oxides of lead]] in air:<ref name="G&E">{{Greenwood&Earnshaw2nd|pages=382-387}}</ref>
:<chem>PbO2->[{293 °C}] Pb12O19 ->[{351 °C}]  Pb12O17 ->[{375 °C}] Pb3O4 ->[{605 °C}] PbO</chem>

Thermal decomposition of [[lead(II) nitrate]] or [[lead carbonate|lead(II) carbonate]] also results in the formation of PbO:
:2&nbsp;{{chem|Pb|(NO|3|)|2}} → 2&nbsp;PbO + 4&nbsp;{{chem|link=nitrogen dioxide|NO|2}} + {{chem|O|2}}
:{{chem|PbCO|3}} → PbO + {{CO2|link=yes}}

PbO is produced on a large scale as an intermediate product in refining raw lead ores into metallic lead. The usual lead ore is [[galena]] ([[lead(II) sulfide]]). At a temperature of around {{convert|1000|C|F|-2}} in air, the sulfide converted to the oxide:<ref>{{cite journal|title=Thermal and XRD analysis of Egyptian galena|journal=Journal of Thermal Analysis and Calorimetry|year=2006|volume=86|issue=2|pages=393–401|last1=Abdel-Rehim|first1=A. M. |doi=10.1007/s10973-005-6785-6|s2cid=96393940}}</ref>
:{{chem2|2 PbS + 2 O2 → 2 PbO + 2 SO2}}

=== From lead ===
Lead combusts at high temperature.<ref name=":0">{{Cite journal |last=Dix |first=J. E. |date=1987-02-01 |title=A comparison of barton-pot and ball-mill processes for making leady oxide |url=https://dx.doi.org/10.1016/0378-7753%2887%2980024-1 |journal=Journal of Power Sources |language=en |volume=19 |issue=2 |pages=157–161 |doi=10.1016/0378-7753(87)80024-1 |bibcode=1987JPS....19..157D |issn=0378-7753}}</ref> According to the Barton pot method, refined molten lead droplets are oxidized under a forced air flow which carries them out to the separation system (e.g. [[Cyclonic separation|cyclonic separators]]) for further processing.<ref name=":0" /><ref name=":1">{{Cite book |last=Pavlov |first=D. |url=https://www.worldcat.org/oclc/978538577 |title=Lead-acid batteries : science and technology : a handbook of lead-acid battery technology and its influence on the product |date=2017 |isbn=978-0-444-59560-7 |edition=2 |location=Saint Louis |oclc=978538577}}</ref>{{Rp|page=245}} Oxides produced by this method are mostly a mixture of α-PbO and β-PbO. The overall reaction, which is conducted at 450&nbsp;°C is:
:{{chem2|Pb + O2 -> 2 PbO}}
Using a [[Ball mill]], lead balls are oxidized in a cooled rotating drum. The oxidation is achieved by collisions of the balls. Just like in Barton pot method, the supply of air and separators may also be used.<ref name=":0" />{{r|:1|p=245}}

==Structure==
As determined by [[X-ray crystallography]], both polymorphs, [[tetragonal]] and [[orthorhombic]] feature a pyramidal four-coordinate lead center. In the tetragonal form the four lead–oxygen bonds have the same length, but in the orthorhombic two are shorter and two longer. The pyramidal nature indicates the presence of a [[stereochemistry|stereochemically]] active [[lone pair]] of electrons.<ref>{{Wells5th}}{{page needed|date=June 2017}}</ref> When PbO occurs in tetragonal lattice structure it is called [[litharge]]; and when the PbO has orthorhombic lattice structure it is called [[massicot]]. The PbO can be changed from massicot to litharge or vice versa by controlled heating and cooling.<ref>A simple example is given in {{cite book |author=Anil Kumar De |title=A Textbook Of Inorganic Chemistry |chapter-url=https://books.google.com/books?id=PpTi_JAx7PgC&pg=PA383 |year=2007 |publisher=New Age International |isbn=978-81-224-1384-7 |pages=383 |chapter=§9.2.6 Lead (Pb): Lead Monoxide PbO }} A more complex example is in {{cite book |first=N.Y. |last=Turova |title=The Chemistry of Metal Alkoxides |chapter-url=https://books.google.com/books?id=rPzaMRjK8pQC&pg=PA115 |date=2002 |publisher=Springer |isbn=978-0-7923-7521-0 |pages=115 |chapter=§9.4 Germanium, tin, lead alkoxides}}</ref> The tetragonal form is usually red or orange color, while the orthorhombic is usually yellow or orange, but the color is not a very reliable indicator of the structure.<ref>{{cite book |first=David John |last=Rowe |title=Lead Manufacturing in Britain: A History |url=https://books.google.com/books?id=ZL4OAAAAQAAJ&pg=PA16 |date=1983 |publisher=Croom Helm |isbn=978-0-7099-2250-6 |pages=16}}</ref> The tetragonal and orthorhombic [[Polymorphism (materials science)|forms]] of PbO occur naturally as rare minerals.

{{gallery|mode=packed-hover
|title=Crystal structure in litharge form<ref name="G&E" /><ref>{{ cite journal | doi = 10.1016/S0167-2738(01)00699-3 | journal = [[Solid State Ionics|Solid State Ion.]] | year = 2001 | volume = 140 | pages = 115–123 | first1 = Caroline | last1 = Pirovano | first2 = M. Saiful | last2 = Islam | authorlink2 = Saiful Islam (professor) | first3 = Rose-Noëlle | last3 = Vannier | first4 = Guy | last4 = Nowogrocki | first5 = Gaëtan | last5 = Mairesse | title = Modelling the crystal structures of Aurivillius phases | issue = 1–2 }}</ref><ref>{{ cite web | url = https://www.ccdc.cam.ac.uk/structures/Search?Ccdcid=1653774&DatabaseToSearch=Published | title = ICSD Entry: 94333 | author = <!--Not stated--> | website = [[Cambridge Structural Database]]: Access Structures | publisher = [[Cambridge Crystallographic Data Centre]] | access-date = 2021-06-01 }}</ref>
|File:PbO-litharge-xtal-Pb-coordination-3D-bs-17.png|Pb coordinates [[square pyramidal molecular geometry|square-pyramidally]]
|File:PbO-litharge-xtal-O-coordination-3D-bs-17.png|O coordinates distorted-[[Tetrahedral molecular geometry|tetrahedrally]]
|File:PbO-litharge-xtal-unit-cell-3D-bs-17.png|Unit cell
|File:PbO-litharge-xtal-3x3x3-3D-bs-17.png|{{math|3×3×3}} unit cells
|File:PbO-litharge-xtal-3x3x3-a-3D-bs-17.png|Along the [[Lattice parameters|{{mvar|a}} axis]]
|File:PbO-litharge-xtal-3x3x3-c-3D-bs-17.png|Along the [[Lattice parameters|{{mvar|c}} axis]]
}}

==Reactions==
PbO is reduced to elemental lead when heated under [[carbon monoxide]] at around {{convert|1200|C|F|-2}}:
:PbO + CO → Pb + {{CO2}}

The red and yellow forms of this material are related by a small change in [[enthalpy]]:
:PbO<sub>(red)</sub> → PbO<sub>(yellow)</sub> {{pad|5em}} Δ''H'' = 1.6&nbsp;kJ/mol

PbO is [[amphoterism|amphoteric]], which means that it reacts with both acids and with bases. With acids, it forms salts of {{chem|Pb|2+}} via the intermediacy of oxo [[cluster chemistry|cluster]]s such as {{chem|[Pb|6|O(OH)|6|]|4+}}. With strong bases, PbO dissolves to form [[plumbite]] (also called plumbate(II)) salts:<ref name="Holl">{{Holleman&Wiberg}}{{page needed|date=June 2017}}</ref>
:PbO + {{H2O}} + {{chem|OH|−}} → {{chem|[Pb(OH)|3|]|−}}

==Applications==
PbO is used extensively in making glass. Depending on the glass, the benefit of using PbO in glass can be one or more of increasing the [[refractive index]] of the glass, increasing the [[Dispersion (optics)|dispersion]] (i.&nbsp;e. reducing the [[Abbe number]]) of the glass, decreasing the [[viscosity]] of the glass, increasing the electrical [[resistivity]] of the glass, and increasing the ability of the glass to absorb [[X-rays]]. Adding PbO to industrial [[ceramics]] (as well as glass) makes the materials more magnetically and electrically inert (by raising their [[Curie temperature]]) and it is often used for this purpose.<ref>Chapter 9, "Lead Compounds", in the book [https://books.google.com/books?id=ASIYuNCp81YC&pg=PA165 ''Ceramic and Glass Materials: Structure, Properties and Processing''], published by Springer, year 2008.</ref> Historically PbO was also used extensively in [[ceramic glaze]]s for household ceramics, and it is still used, but not extensively any more. Other less dominant applications include the [[vulcanization]] of rubber and the production of certain pigments and paints.<ref name=Ullmann>{{Ullmann|first=Dodd S.|last=Carr|year=2005|title=Lead Compounds|doi=10.1002/14356007.a15_249}}</ref> PbO is used in [[cathode-ray tube]] glass to block [[X-ray]] emission, but mainly in the neck and funnel of the tube, because it can cause discoloration when used in the faceplate. [[Strontium oxide]] and [[Barium oxide]] are preferred for the faceplate.<ref>{{Cite book|url=https://books.google.com/books?id=FvkqeL4IDMwC&q=lead+funnel&pg=PA9|title=Image Performance in CRT Displays|first=Kenneth|last=Compton|date=5 December 2003|publisher=SPIE Press|isbn=9780819441447|via=Google Books}}</ref>

The consumption of lead, and hence the processing of PbO, correlates with the number of automobiles, because lead remains the key component of automotive [[lead–acid battery|lead–acid batteries]].<ref>{{Ullmann|first1=Charles A.|last1=Sutherland|first2=Edward F.|last2=Milner|first3=Robert C.|last3=Kerby|first4=Herbert|last4=Teindl|first5=Albert|last5=Melin|first6=Hermann M.|last6=Bolt|title=Lead|doi=10.1002/14356007.a15_193.pub2}}</ref>

===Niche or declining uses===
A mixture of PbO with [[glycerine]] sets to a hard, waterproof [[cement]] that has been used to join the flat glass sides and bottoms of [[aquarium]]s, and was also once used to seal glass panels in window frames. It is a component of [[lead paint]]s.

PbO was one of the raw materials for [[century egg]]s, a type of [[Chinese cuisine|Chinese]] preserved [[Egg as food|egg]]. but it has been gradually replaced due to health problems. It was an unscrupulous practice in some small factories but it became rampant in [[China]] and forced many honest manufacturers to label their boxes "lead-free" after the scandal went mainstream in 2013.

In powdered tetragonal litharge form, it can be mixed with [[linseed oil]] and then boiled to create a weather-resistant [[sizing]] used in [[gilding]]. The litharge would give the sizing a dark red color that made the gold leaf appear warm and lustrous, while the linseed oil would impart adhesion and a flat durable binding surface.

PbO is used in certain [[condensation reaction]]s in [[organic synthesis]].<ref>{{OrgSynth| last=Corson |first=B. B. |year=1936 |title=1,4-Diphenylbutadiene |volume=16 |pages=28 |collvol=2 |collvolpages=229 |prep=CV2P0229}}</ref>

PbO is the input photoconductor in a video camera tube called the [[Plumbicon]].

==Health issues==
[[File:PbOlabel.jpg|thumb|left]]
{{Main|Lead poisoning}}
Lead oxide is toxic and irritate to skin, eyes, and respiratory tract. It affects gum tissue, the central nervous system, the kidneys, the blood, and the reproductive system. It can [[bioaccumulate]] in plants and in mammals.<ref>{{cite web |url= http://www.ilo.org/safework_bookshelf/english?d&nd=857171610 |title= Lead(II) oxide |access-date= 2009-06-06 |publisher= International Occupational Safety and Health Information Centre |archive-url= https://web.archive.org/web/20111215095749/http://www.ilo.org/safework_bookshelf/english?d&nd=857171610 |archive-date= 2011-12-15 |url-status= dead }}</ref>

{{Clear}}

==References==
{{Reflist}}

==External links==
*[https://www.atsdr.cdc.gov/csem/csem.html Case Studies in Environmental Medicine - Lead Toxicity]
*[https://www.atsdr.cdc.gov/csem/csem.html ToxFAQs: Lead]
*[https://web.archive.org/web/20080111154608/http://www.npi.gov.au/database/substance-info/profiles/50.html National Pollutant Inventory - Lead and Lead Compounds Fact Sheet]
*[http://www.webelements.com/compounds/lead/lead_oxide.html Webelements PbO]

{{Lead compounds}}
{{Oxides}}

[[Category:Amphoteric compounds]]
[[Category:Lead(II) compounds]]
[[Category:Oxides]]