270 
POWER OP LITHARGE, ETC. 
ART. LXXIV— ON THE POWER OF DISSOLVING OXYGEN, 
POSSESSED BY LITHARGE IN A STATE OF FUSION, AND 
ON SEVERAL PECULIARITIES WHICH ACCOMPANY THE 
PRODUCTION OF LITHARGE BY CUPELLATION QN A LARGE 
SCALE. 
By M. F. Leblanc. 
We know that the cnpellation which is practised in estab- 
lishments where lead is prepared from the ore, is an opera- 
tion, the object of which is to separate the silver from the 
lead, by eliminating the latter metal in the state of an 
oxide. Cupellation in the large way, or refining, as it is 
called, in some manufactories differs from the cupellation of 
the assay offices, on account of the litharge, or protoxide of 
lead being formed by the action of the oxygen of the atmos- 
phere on the lead in a state of fusion at a high temperature, 
instead of being eliminated by absorption into the substance 
of cupel, it flows out of the furnace as fast as it is produced 
along a kind of gutter, which is constantly kept level with 
the surface of the melted metal. The substance that forms 
the cupel of the furnace, ought, as much as possible, to resist 
the absorption or dissolving action of litharge in a state of 
fusion. 
The oxygen of the atmosphere is projected on the surface 
of the metal by a forced current of air. 
During a visit I lately made to Poultaouen, I had an op- 
portunity of being present at many of the operations for the 
refining of lead, containing silver, and of making several 
observations which perhaps will appear not devoid of 
scientific interest.* 
* The process of refining at Poultaouen is usually performed upon 
about a ton of lead at a time; at the end of about eight or ten hours 
the fusion is complete, and they begin to skim the pot : soon afterwards 
