Obfervations on Lead Ore. 875 
Arfenic is extracted from a particular ore in Saxony, by 
roafting the ore in a furnace, which has a long horizon- 
tal chimney; the chimney is large, has many windings 
and angles, that the arfenical vapour which arifes from 
the ore may be the more ealily condenfed: the arfenic 
attaches itfelf like foot to the fides of the chimney, and is 
from time to time fwept out. It is very probable, that by 
fome fuch contrivance the fulphur contained in lead ore 
might be collected. The fmelters call every thing ful- 
phur which is volatilized during the roafting or fluxing 
of an ore; but none of th.ofe with whom I have con- 
yerfed had any notion that common fulphur could be fe- 
parated from lead ore. 
The greyifh calx which remained upon the iron after 
the fulphur was confumed, was put upon a piece of lighted 
charcoal ; the heat of the charcoal being quickened by 
blowing upon it, a great number of globules of lead were 
formed upon its furface. From hence it appears, that 
this calx is not an unmetallic earth contained in the ore, 
which the acid of nitre could not diflolve ; but a calx of 
lead, probably produced by the violent adtion of the acid, 
and which, by the addition of phlogifton, may be exhi- 
bited in its metallic form. The quantity of this calx de- 
pends much upon the adtion of the acid upon the ore; 
if that adtion is violent, the calx is in greater abundance 
5 Q 2 than 
