Litharge, or Lithargyrum, a preparation of lead, consisting of soft flakes of a yellowish or reddish colour. It is obtained by expo>ing calcined lead to a brisk fire, sufficiently strong to melt it into an oil; which, on cooling, concretes into a flaky matter. Thus, according to the different degrees of heat, it assumes a pale or deep red colour : the former is generally called litharge of silver; and the latter, litharge of gold.
This preparation is of extensive utility for roasting gold, silver, or copper ores, as it liquefies all earthy and extraneous matters into glass, and thus the metal is more easily separated. Litharge is also employed by potters, for glazing their wares (though such vessels are un wholesome, see vol. ii. p. 377) ; and likewise in the composition of certain glasses; because it is not only fusible in itself, but contributes to the fusion of other substances.—Lastly, it may be revived into lead : and thus considerable quantities, which are produced by refining metals, are again converted into their original form, by melting them upon burning coals
Litharge-plaster is prepared by boiling two parts of olive-oil with. one part of litharge, over a moderate fire; adding water, and constantly stirring the mixture, till the two former are duly incorporated. This composition, which was formerely called Diachylon, is usually applied in excoriations of the skin, slight wounds; etc. Its action is so far beneficial, as it keeps the injured part soft and somewhat warm, while it excludes the external air; though such piaster ought to be employed with due caution.