Lead carbide is a hypothetical chemical compound of
carbon
Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon mak ...
and
lead
Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...
. Lead and elemental carbon do not normally combine, even at very high temperatures.
Modern literature on lead carbide is almost non-existent.
Production
J. F. Durand reported in 1923 the synthesis of lead carbide from
calcium carbide
Calcium carbide, also known as calcium acetylide, is a chemical compound with the chemical formula of Ca C2. Its main use industrially is in the production of acetylene and calcium cyanamide.
The pure material is colorless, while pieces of te ...
CaC
2 by treatment with an aqueous solution of
lead(II) acetate
Lead(II) acetate (Pb(CH3COO)2), also known as lead acetate, lead diacetate, plumbous acetate, sugar of lead, lead sugar, salt of Saturn, or Goulard's powder, is a white crystalline chemical compound with a slightly sweet taste. Like many other l ...
Pb(CH
3COO)
2, but this result was not reproduced.
[
William A Frad (1968), ''Metal Carbides''. In ]Harry Julius Emeléus
Harry Julius Emeléus CBE, FRS (22 June 1903 – 2 December 1993) was a leading English inorganic chemist and a professor in the department of chemistry, Cambridge University.
Early life
Emeléus was born in Poplar, London on 22 June 1903, t ...
, ''Advances in inorganic chemistry and radiochemistry.'' volume 12, page 213
Online version
at books.google.com, accessed on 2010-01-17.
[
J. F. Durand (1923), Comptes Rendus... cited by W. A. Frad.
]
A 2007 textbook repeats this claim, describing lead carbide as a green powder with formula PbC
2 that is decomposed by
hydrochloric acid
Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid
Acid strength is the tendency of an acid, symbol ...
HCl to
acetylene C
2H
2 and
lead(II) chloride
Lead(II) chloride (PbCl2) is an inorganic compound which is a white solid under ambient conditions. It is poorly soluble in water. Lead(II) chloride is one of the most important lead-based reagents. It also occurs naturally in the form of the mi ...
PbCl
2.
[
R. K. Sharma (2007) ''Chemistry of Hydrides and Carbides.'' Discovery Publishing House, New Delhi. .
]
A compound analyzed as lead carbide PbC
2 has also been obtained accidentally, as a thin layer (about 10
μm thick) on the inner wall of a
graphite
Graphite () is a crystalline form of the element carbon. It consists of stacked layers of graphene. Graphite occurs naturally and is the most stable form of carbon under standard conditions. Synthetic and natural graphite are consumed on lar ...
crucible that had been used to heat a lead-
bismuth
Bismuth is a chemical element with the symbol Bi and atomic number 83. It is a post-transition metal and one of the pnictogens, with chemical properties resembling its lighter group 15 siblings arsenic and antimony. Elemental bismuth occurs ...
eutectic alloy for 100 hours at 1073
K in a
helium
Helium (from el, ἥλιος, helios, lit=sun) is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic table. ...
atmosphere.
[
P. K. Wattal (2007) ''Nuclear Fuel Cycle.'' BARC Highlights, Bhaba Atomic Research Center]
Chapter 4: Basic Studies
[
A. K. Sengupta, R. K. Bhagat, A. Laik, G. B. Kale, T. Jarvis, S. Majumdar, H. S. Kamath (2006): "Out-of-pile chemical compatibility of Pb–Bi eutectic alloy with Graphite". ''Zeitschrift für Metallkunde'', volume 97, issue 6, pages 834–837. ]
Pyrophoric lead
Several reports of "lead carbide" synthesis appeared in the early 19th century, and were widely cited and copied into textbooks during the next few decades. In 1820, for instance, a certain John claimed to have sublimated a black carbide of lead from finely divided mixture of lead and
charcoal,
[
John (1820). Berlinisches Jahrbuch der Pharmacie, p. 320. Cited by Gmelin (1851) with a "?".
] but this claim apparently was never reproduced.
Also in 1820,
Berzelius claimed that the
pyrolysis
The pyrolysis (or devolatilization) process is the thermal decomposition of materials at elevated temperatures, often in an inert atmosphere. It involves a change of chemical composition. The word is coined from the Greek-derived elements ''py ...
(decomposition by heat) of
iron-lead cyanide resulted in a double iron and lead carbide, FeC
4·2PbC
4.
[
Jöns Jacob Berzelius (1820)]
''Des rercherches sur la composition des prussiates ou des hydrocyanates ferrugineux.''
Annales de chimie et de physique, volume 15
In 1823
Göbel from Jena obtained, by pyrolysis of
lead tartrate in a closed vessel, a black powder that ignited spontaneously in contact with air, and believed it to be a carbide of lead.
[
Friedmann Göbel (1823). Archiv des Apotheker-Vereins, 11, p.347.
][
Perdonnet (1824)]
''Nouveau Pyrophore''
Short note in Bulletin universal des sciences et de l'índustrie, Volume 2, Paris, p.30
[
Anonymous note (1824)]
''New Pyrophorus of Tartrate of Lead''
The Edinburgh Philosophical Journal, Volume 10 issue 20, p. 368
This product still provides a popular school demonstration of
pyrophoricity
A substance is pyrophoric (from grc-gre, πυροφόρος, , 'fire-bearing') if it ignites spontaneously in air at or below (for gases) or within 5 minutes after coming into contact with air (for liquids and solids). Examples are organolith ...
.
[
Bassam Z. Shakhashiri (1983)]
''Pyrophoric lead''
in ''Chemical demonstrations: a handbook for teachers of chemistry'', Univ of Wisconsin Press, p. 94
Shortly thereafter, Proust obtained a similar product from lead acetate
and Berzelius obtained one from
lead cyanide.
[
]Leopold Gmelin
Leopold Gmelin (2 August 1788 – 13 April 1853) was a German chemist. Gmelin was a professor at the University of Heidelberg He worked on the red prussiate and created Gmelin's test, and wrote his ''Handbook of Chemistry'', which over successi ...
(1851), ''Hand-book of Chemistry''. Translated by Henry Watts. Cavendish Society
[
Jöns Jacob Berzelius (1846), ''Traité de Chimie Minérale, Végetale et Animale'', vol. 2. Transl. by F.H. Esslinger. Firmin Didot, Paris.
][
William Thomas Brande and Alfred Swayne Taylor (1867),''Chemistry''. 2nd American edition, Henry C. Lea, Philadelphia.
]
However, by 1870 those pyrophoric residues came to be regarded as an "intimate mixture" of carbon and lead; and the existence of lead carbide was considered unproven.
[ John Percy (1870)]
''The Metallurgy of Lead, including Desiverization and Cupellation''
J.Murray, London.
References
{{DEFAULTSORT:Lead Carbide
Carbides
Lead(II) compounds
Hypothetical chemical compounds