Lead(II) oxide

Lead(II) oxide, also called lead monoxide, is the inorganic compound with the molecular formula PbO. PbO occurs in two polymorphs: litharge having a tetragonal crystal structure, and massicot having an orthorhombic crystal structure. Modern applications for PbO are mostly in lead-based industrial glass and industrial ceramics, including computer components. It is an amphoteric oxide.[3]

Lead(II) oxide
Names
IUPAC name
Lead(II) oxide
Other names
Lead monoxide
Litharge
Massicot
Murda sang
Plumbous oxide
Galena
Identifiers
ChemSpider
ECHA InfoCard 100.013.880
RTECS number
  • OG1750000
UNII
UN number 3288
Properties
PbO
Molar mass 223.20 g/mol
Appearance red or yellow powder
Density 9.53 g/cm3
Melting point 888 °C (1,630 °F; 1,161 K)
Boiling point 1,477 °C (2,691 °F; 1,750 K)
0.017 g/L[1]
Solubility insoluble in dilute alkalis, alcohol
soluble in concentrated alkalis
soluble in HCl, ammonium chloride
4.20×10−5 cm3/mol
Structure
Tetragonal, tP4
P4/nmm, No. 129
Hazards
Safety data sheet ICSC 0288
Repr. Cat. 1/3
Toxic (T)
Harmful (Xn)
Dangerous for the environment (N)
R-phrases (outdated) R61, R20/22, R33, R62, R50/53
S-phrases (outdated) S53, S45, S60, S61
NFPA 704 (fire diamond)
Flammability code 0: Will not burn. E.g. waterHealth code 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
0
3
0
Flash point Non-flammable
Lethal dose or concentration (LD, LC):
1400 mg/kg (dog, oral)[2]
Related compounds
Other anions
 Lead sulfide
Lead selenide
Lead telluride
Other cations
 Carbon monoxide
Silicon monoxide
Tin(II) oxide
Related lead oxides
 Lead(II,II,IV) oxide
Lead dioxide
Related compounds
 Thallium(III) oxide
Bismuth(III) oxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YN ?)
Infobox references

Preparation

PbO may be prepared by heating lead metal in air at approximately 600 °C (1,100 °F). At this temperature it is also the end product of oxidation of other oxides of lead in air:[4]

PbO
2 293 °C→ Pb
12O
19 351 °C→ Pb
12O
17 375 °C→ Pb
3O
4 605 °C→ PbO

Thermal decomposition of lead(II) nitrate or lead(II) carbonate also results in the formation of PbO:

2 Pb(NO
3)
2 → 2 PbO + 4 NO
2 + O
2
PbCO
3 → PbO + CO
2

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 1,000 °C (1,800 °F) the sulfide is converted to the oxide:[5]

2 PbS + 3 O
2 → 2 PbO + 2 SO
2

Metallic lead is obtained by reducing PbO with carbon monoxide at around 1,200 °C (2,200 °F):[6]

PbO + CO → Pb + CO
2

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 stereochemically active lone pair of electrons.[7] 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.[8] 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.[9] The tetragonal and orthorhombic forms of PbO occur naturally as rare minerals.

Reactions

The red and yellow forms of this material are related by a small change in enthalpy:

PbO(red) → PbO(yellow)   ΔH = 1.6 kJ/mol

PbO is amphoteric, which means that it reacts with both acids and with bases. With acids, it forms salts of Pb2+
 via the intermediacy of oxo clusters such as [Pb
6O(OH)
6]4+
. With strong bases, PbO dissolves to form plumbite (also called plumbate(II)) salts:[10]

PbO + H
2O + OH−
 → [Pb(OH)
3]−

Applications

The kind of lead in lead glass is normally PbO, and 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, 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.[11] Historically PbO was also used extensively in ceramic glazes 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.[3] PbO is used in cathode ray tube glass to block X-ray emission, but mainly in the neck and funnel because it can cause discoloration when used in the faceplate. Strontium oxide is preferred for the faceplate.

The consumption of lead, and hence the processing of PbO, correlates with the number of automobiles, because it remains the key component of automotive lead-acid batteries.[12]

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 aquariums, and was also once used to seal glass panels in window frames. It is a component of lead paints.

PbO was used to speed up the process to turn more profit for less time and artificially increase the quality of century eggs, a type of Chinese preserved egg. 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 reactions in organic synthesis.[13]

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

Health issues
Main article: Lead poisoning

Lead oxide may be fatal if swallowed or inhaled. It causes irritation to skin, eyes, and respiratory tract. It affects gum tissue, central nervous system, kidneys, blood, and reproductive system. It can bioaccumulate in plants and in mammals.[14]

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References
  1. Blei(II)-oxid. Merck
  2. "Lead compounds (as Pb)". Immediately Dangerous to Life and Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  3. Carr, Dodd S. (2005). "Lead Compounds". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a15_249.
  4. Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
  5. Abdel-Rehim, A. M. (2006). "Thermal and XRD analysis of Egyptian galena". Journal of Thermal Analysis and Calorimetry. 86 (2): 393–401. doi:10.1007/s10973-005-6785-6.
  6. Lead Processing @ Universalium.academic.ru. Alt address: Lead processing @ Enwiki.net.
  7. Wells, A. F. (1984), Structural Inorganic Chemistry (5th ed.), Oxford: Clarendon Press, ISBN 0-19-855370-6
  8. A simple example is given in Anil Kumar De (2007). "§9.2.6 Lead (Pb): Lead Monoxide PbO". A Textbook Of Inorganic Chemistry. New Age International. p. 383. ISBN 978-81-224-1384-7. A more complex example is in Turova, N.Y. (2002). "§9.4 Germanium, tin, lead alkoxides". The Chemistry of Metal Alkoxides. Springer. p. 115. ISBN 978-0-7923-7521-0.
  9. Rowe, David John (1983). Lead Manufacturing in Britain: A History. Croom Helm. p. 16. ISBN 978-0-7099-2250-6.
  10. Holleman, Arnold Frederik; Wiberg, Egon (2001), Wiberg, Nils (ed.), Inorganic Chemistry, translated by Eagleson, Mary; Brewer, William, San Diego/Berlin: Academic Press/De Gruyter, ISBN 0-12-352651-5
  11. Chapter 9, "Lead Compounds", in the book Ceramic and Glass Materials: Structure, Properties and Processing, published by Springer, year 2008.
  12. Sutherland, Charles A.; Milner, Edward F.; Kerby, Robert C.; Teindl, Herbert; Melin, Albert; Bolt, Hermann M. "Lead". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a15_193.pub2.
  13. Corson, B. B. (1936). "1,4-Diphenylbutadiene". Organic Syntheses. 16: 28.; Collective Volume, 2, p. 229
  14. "Lead(II) oxide". International Occupational Safety and Health Information Centre. Archived from the original on 2011-12-15. Retrieved 2009-06-06.
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