Lead carbide

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Lead carbide is a hypothetical chemical compound of carbon and lead.

Production[edit]

Lead and elemental carbon do not normally combine, even at very high temperatures.[1] Modern literature on lead carbide is almost non-existent.

J. F. Durand reported in 1923 the synthesis of lead carbide from calcium carbide CaC2 by treatment with an aqueous solution of lead(II) acetate Pb(CH3COO)2, but this result was not reproduced.[2][3] A recent textbook repeats this claim, and describes it as a green powder with formula PbC2 that is decomposed by hydrochloric acid HCl to acetylene C2H2 and lead(II) chloride PbCl2.[4]

A compound analyzed as lead carbide PbC2 has also been obtained accidentally as a thin layer (about 10 μm thick) on the inner wall of a graphite crucible that had been used to heat a lead-bismuth eutectic alloy for 100 hours at 1073 K in a helium atmosphere.[5]:p.27

Pyrophoric lead[edit]

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,[6][7] but this claim apparently was never reproduced.[1]:p.67 Also in 1820, Berzelius claimed that the pyrolysis (decomposition by heat) of iron-lead cyanide resulted in a double iron and lead carbide, FeC4·2PbC4.[8] 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.[9][10][11] This product still provides a popular school demonstration of pyrophoricity.[12] Shortly thereafter, Proust obtained a similar product from lead acetate[6] and Berzelius obtained one from lead cyanide.[6]:p.122[13][14]:p.436 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.[1]:p.67

References[edit]

  1. ^ a b c John Percy (1870), The Metallurgy of Lead, including Desiverization and Cupellation. J.Murray, London.
  2. ^ William A Frad (1968), Metal Carbides. In Harry Julius Emeléus, Advances in inorganic chemistry and radiochemistry. volume 12, page 213. Online version at books.google.com, accessed on 2010-01-17.
  3. ^ J. F. Durand (1923), Comptes Rendus... cited by W. A. Frad.
  4. ^ R. K. Sharma (2007) Chemistry of Hydrides and Carbides. Discovery Publishing House, New Delhi. ISBN 81-8356-227-2.
  5. ^ P. K. Wattal (2007) Nuclear Fuel Cycle. BARC Highlights, Bhaba Atomic Research Center, Chapter 4: Basic Studies
  6. ^ a b c Leopold Gmelin (1851), Hand-book of Chemistry. Translated by Henry Watts. Cavendish Society
  7. ^ John (1820). Berlinisches Jahrbuch der Pharmacie, p. 320. Cited by Gmelin (1851) with a "?".
  8. ^ Jöns Jacob Berzelius (1820), Des rercherches sur la composition des prussiates ou des hydrocyanates ferrugineux. Annales de chimie et de physique, volume 15
  9. ^ Friedmann Göbel (1823). Archiv des Apotheker-Vereins, 11, p.347.
  10. ^ Perdonnet (1824). Nouveau Pyrophore. Short note in Bulletin universal des sciences et de l'índustrie, Volume 2, Paris, p.30
  11. ^ Anonymous note (1824), New Pyrophorus of Tartrate of Lead. The Edinburgh Philosophical Journal, Volume 10 issue 20, p. 368
  12. ^ Bassam Z. Shakhashiri (1983), Pyrophoric lead; in Chemical demonstrations: a handbook for teachers of chemistry, Univ of Wisconsin Press, p. 94
  13. ^ Jöns Jacob Berzelius (1846), Traité de Chimie Minérale, Végetale et Animale, vol. 2. Transl. by F.H. Esslinger. Firmin Didot, Paris.
  14. ^ William Thomas Brande and Alfred Swayne Taylor (1867),Chemistry. 2nd American edition, Henry C. Lea, Philadelphia.