Lead . 
217 
mixed with clean small- coal, and exposed to a heat just 
sufficient to fuse the litharge. The metal as it is reduced 
flows through an aperture into an iron pot, and is cast into 
pigs for sale. During the reducing, care is taken to keep 
the whole surface of the litharge in the furnace covered 
with small- coal. 
In some smelt works, instead of a reverberatory fur- 
nace for reducing, a blast furnace is made use of, on ac- 
count of the greater produce, but the lead so reduced is 
never so pure as that made in the wind furnace. The 
oxyds of the metals, which require a greater heat to reduce 
than the lead, are in the blast furnace generally reduced 
with it. 
The volatile oxyds, as zinc, antimony, and arsenic, are 
mostly carried off by evaporation during refining ; a con- 
siderable portion of the oxyd of lead itself is carried 
off by evaporation, making the interior of the furnace so 
misty and obscure, that a person unused to refining can- 
not see more than a few inches into it. 
A considerable portion of these oxyds are driven by 
the blast of the bellows through the feeding aperture, and 
would be dissipated in the refining-house, to the great in- 
jury of the workmen’s healths; to prevent their ill effects 
the arch or dome over the feeding hole is erected to carry 
the fume into the stack of the furnace. 
15 Nicholson^ 1. 
PROPERTIES of the metal Lead. Lead obtained 
free from any other metallic mixture, (as by precipitating 
nitrat or acetat of lead by zinc) is when recently melted 
of a bright bluish- white colour, which sooh tarnishes on 
exposure to air : but when once tarnished, lasts a long 
time exposed to the weather, for it does not decompose 
water as iron and copper do. It is the softest ^gf the com- 
Vol. III. Ee 
