212 
Lead* 
Cupola Smelting . 
For the method of smelting lead by the cupola furnace 
as principally practised in Derbyshire, I refer to Watson’s 
Chemical Essays ; a more correct or interesting account 
cannot be given, (already inserted).— 38 Phil. Mag . 371. 
The process for refining Lead , as practised in England \ 
In a letter from Mr. John Sadler . 
WITH TWO ENGRAVINGS.^ 
MY dear Sir — -Citizen Duhamel, in his Memoir on 
the refining of Lead in the large way, has given a sketch 
of the process used in England ; if you think the follow- 
ing more detailed description will be acceptable to the 
readers of the Philosophical Journal, it is at your ser- 
vice. 
The object of refining lead is not merely on account 
of the silver it contains, but to procure it as free as pos- 
sible from the other metals with which it is usually al- 
loyed, and to procure litharge. The silver is only an 
object, so far as it helps to pay the expense of refin- 
ing. 
The lead produced at the smelting hearths or furnaces 
in England is never perfectly pure ; it is always alloyed 
with a portion of silver, and most commonly with one or 
most of the following metals ; namely, zinc, antimony, 
copper, and arsenic ; which render it unfit for some of the 
purposes to which lead is applied. 
The operation of refining is founded on the facility 
with which lead is oxydated when exposed to heat in 
contact with atmospheric air, and the peculiar properties 
the oxyds of lead possess ; being easily fused, and in that 
state oxydating and combining with most of the metals ; 
gold, silver, and platina excepted, 
* These will be given in the next number. 
