483 
De snip filtration of Metals . 
The roasting of pyritous copper in the reverberatory furnace 
produces the same phenomena, and seems as if it would admit of 
a much more complete separation of the sulphur, than that pro- 
duced in the open air. If it were not so, it would no doubt be 
owing to the difficulty of hindering the agglutination of the sul- 
phuret produced by the elevation of temperature, owing to th^ 
rapid and inevitable combustion of a great quantity of sulphur. 
I come now to speak of a furnace, in which we effect at the 
same time both the melting and the roasting (to a certain degree) 
of pyritous copper : this is the method practised at Falhun in 
Sweden,* and is done with an inner crucible, which receives the 
produce of a flux of 24 or 48 hours, and in which a separation, or 
rather a combustion, of the sulphur takes place. The wind of 
the bellows passes over the surface with sufficient force for re- 
moving the scoriae, and burning a part of the sulphur on the sur- 
face : the iron is thus oxydized, and quartz is added in order to 
vitrify it in proportion as the roasting goes on.f It is thus that 
* We find the following observations in the Voyages Metallurgiques , by 
Jars, tome iii, pages 55 Sc seq. “ The dux of the mineral roasted a single 
time, is effected in a furnace which has an inner bason destined to contain the 
produce of the operation.”-— “ When it is heated, it is charged with a good 
deal of scorise from the flux of black copper, with quartz and a little mineral.” 
“ They do not mix the quartz With the mineral, but only add it when there 
are any fears of mischief in the inner bason.” — “The fusion of the roasted 
pieces ( mattes ) is effected in the same kind of furnace, but smaller.”— *“ The 
substances must remain a longer time in the furnace, which must not be 
©pened until the end of twice twenty-four hours. They then extract a very 
few rich mattes, but a very large pig of black copper.” — “This method of 
melting the pyrites is certainly the otsly one that can be used, and which, in, 
spite of the inconveniences it presents, may nevertheless be advantageous.” 
“ Another very precious advantage is a concentration of the metal contained 
in the Jhrid matter which is contmually agitated by the wind of the bellows. They 
extract a smaller quantity of mattes, but they are richer. We confess our sur- 
prise at the flux of black copper, when we see the small quantity of rich mat - 
tes whieh comes from a very inferior sort of ore, and which does not even seem 
to have been roasted .” We should be of M. Jars’ opinion, that this method of 
melting pyritous copper is one of the best, if more copper was not volatilized 
than by the other process: but if, as I think, we may substitute the reverbe- 
ratory furnace for that used at Falhun, and in other respects following up the 
same series of operations, there would certainly be great advantages derived 
gyer fusion in the hand furnace. 
f Swedenborg ( de cupro ) thus expresses himself: (e Plurirna ejus ars 
(meaning the melters) in eo consistit , ui lapidem siiiceum, justo tempore et 
modo j sciat off err e? 
Vo l. in. 3 o 
