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black lead

black lead

black lead: see graphite.
or plumbago or black lead

Mineral allotrope of carbon. It is dark gray to black, opaque, and very soft. Its layered structure, with rings of six atoms arranged in widely spaced parallel sheets, gives it its slippery quality. It occurs in nature and is used (mixed with clay) as the “lead” in pencils. It is also used in lubricants, crucibles, polishes, arc lamps, batteries, brushes for electric motors, and nuclear reactor cores.

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Lead oxide may refer to:

Less common lead oxides are:

  • Lead(II,IV) oxide, Pb2O3, lead sesquioxide
  • Pb12O19 (monoclinic, dark-brown or black crystals)
  • The so-called black lead oxide, which is a mixture of PbO and fine-powdered metal Pb and used in the production of lead acid batteries.

The sequence of the thermal transformation between the oxides in air (starting from PbO2) is as follows:

PbO_2 stackrel{rm 293 ,^{circ}mathrm{C}} {longrightarrow} Pb_{12} O_{19} stackrel{rm 351 ,^{circ}mathrm{C}} {longrightarrow} Pb_{12} O_{17} stackrel{rm 374 ,^{circ}mathrm{C}} {longrightarrow} Pb_3 O_4 stackrel{rm 605 ,^{circ}mathrm{C}} {longrightarrow} PbO


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