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from copper more advantageously than by any otherknown method*

The way of procedure is as follows. Some litharge,or any other calx of lead, is melted with about an equalquantity of sulphur, with which it unites into a sparklingmass, of a femimetallic aspect, and nearly of the samequality with the common lead ores. The copper beingbrought into fusion, this mixture is thrown upon it, bya little at a time, till the quantity of lead becomes nearlyequal to that of the copper: the copper absorbs the sul-phur from the lead, and the lead, being in a state of calx,remains uniformly blended with the sulphurated copper.A little powdered charcoal is then thrown in, and thewhole well stirred with an iron rod : the lead is immedi-ately revived into its metallic form, and sinking to thebottom carries the gold with it; neither lead nor goldhaving any affinity to sulphurated copper. The effect isthe same when the copper is first sulphurated, and thelitharge or calx of lead added to this mixture ; and pro-bably gold might be separated in the same manner fromsulphurated iron.

VIII. Separation of gold from gilt works.

The solubility of gold and the indiffolubility of silverin aqua regia affords a principle on which gold may beseparated from the surface of silver ; and on this founda-tion different processes have been contrived, of whichthe two following appear to be the best. Some powderedsal ammoniac, moistened with aqua fortis into the con-sistence of a paste, is spread upon the gilt silver, andthe piece heated, till the matter smokes and becomesnearly dry : being then thrown into water, it is rubbedwith a scratch brush, composed of fine brass wire bound5 together,