Lead . 
197 
in the cupola furnace, in order that the calcined lead 
might be converted into lead, by uniting itself to the in- 
flammable principle of the charcoal?*— Iron will not unite 
with lead, but it readily unites with sulphur, and, when 
added to a mixture of lead and sulphur, it will absorb the 
sulphur, leaving the lead in its metallic form ; might it 
not be useful to flux sulphureous lead ores in conjunction 
with the scales or other refuse pieces of iron, or even with 
some sorts of iron ore ?— The smelter’s great care should 
be to extract as much lead as possible at the first opera- 
tion of smelting the ore, and to leave the slag as poor as 
possible ; but if he should still find either the slag of the 
cupola furnace, or that of the hearth furnace, containing 
much lead (as that even of the hearth furnace certainly 
does), he may, perhaps, find it worth his while to reduce 
the slag into a powder by a stamping mill, or by laying it 
in highways to be ground by the carts, or by some other 
contrivance, and then he may separate the stony part of 
the slag from the metallic, by washing the whole in wa- 
ter, inasmuch as the metallic part is far heavier than the 
other. 
I estimated the weights of several pieces of slag, and 
found them to differ very much from each other ; this 
difference is principally to be attributed to the different 
quantities of lead left in them. 
Weight of a cubic foot of 
Avoir. 02 « 
Slag from a cupola furnace where no 
lime was used - 
Black slag from a hearth furnace 
Another piece - 
Black slag from another hearth fur- 
nace-struck fire with steel 
Black glass slag - - - _ 337L 
[3 Watson's Chem . Essa?js , 272—298, 
3742 
3652 
3612 
3378 
j This is on the Stahiian or phlogistic theory. T. C. 
