Lead . 
243 
a carbonat of lead, though the rationale of the process by 
which it is made, would point out the formation of the car- 
bonic acid, during the process of refining lead. 
By accident I mislaid the following important memoir 
on the refining of lead andphe making of Cupells or Tests. 
It is from the Journal des Mines, No. 64. 
Memoir on the Refining of Lead; with some reflections on 
the inconvenience of Ash Cupells ; and the description 
of a new and economical method of constructing Cupells 
or Refining V essels : read in the French National Insti- 
tute . By C. Duhamel, Member of the Institute and 
Inspector of Mines . 
It is well known, that to separate silver from lead, a 
metallurgic process called refining or cupellation, per- 
formed in a vessel called a cupell, has been employed : 
it is known also that this vessel is composed either of the 
ashes of the bones of animals, or of those of vegetables, 
after they have been lixiviated, to free them from the sa- 
line matters which they may contain. 
The great quantity of wood-ashes which must be em- 
ployed in the construction of cupells, and the difficulty 
of obtaining them, long ago induced me to endeavour to 
discover a simpler and less expensive method of con- 
structing the vessels in question. The old chemists having 
observed that lead becomes oxydated, or reduced into 
what is called litharge , when exposed to heat, or the con- 
tact of the atmospheric air, while the silver united to it re- 
tains its metallic form, nothing seemed necessary but to 
find the means of separating these two metals. They 
were conducted to the method of accomplishing this by 
observing that the oxyd of lead, in its state of liquefaction, 
easily penetrates the substances which are in contact with 
it, and especially bone-ashes, without deforming the ves- 
