4-56 Mr. J. Taylor's Lectures on Metallurgy. 



by a heat which melts it out from the copper. This process 

 is called Eliquation. The silver is separated from the lead 

 afterwards by cupellation, which is a process adapted also to 

 procuring gold. 



Where metals in the state of oxide are to be reduced into 

 their malleable or pi'oper form, it is done by fusion in con- 

 tact with carbon, as was described in the case of tin ores; and 

 they are therefore mixed with smallcoal, wood, or charcoal. 

 The oxygen leaves the metal, and forms, v/ith tiie carbon, car- 

 bonic acid, which escapes. Thus litharge, which is the oxide 

 of lead obtained by cupellation, is again brought into the stale 

 of lead; this process is called Reviving. 



Iron in its perfect state is nearl}' infusible, and it must be 

 largely combined with carbon to make it melt freely, on which 

 account we see the use of smelting the ores in contact with 

 coke. The carbon is separated when it is converted into bar 

 iron ; and, in converting this into steel, carbon is again made 

 to combine in another iproportion. 



Copper requires, after it is freed as much as possible from 

 the other metals, a peculiar treatment with charcoal, and a 

 continued melting heat; which process is called Toughening. 

 The melted metal is much stirred with wood j)oles, and after 

 a time assumes the required properties of extending under the 

 hammer without being subject to crack. The theory of this 

 process is rather obscure. 



The volatile metals would of course be dissij^ated if they 

 were exposed to the heat requisite for melting them out from 

 the substances with which they are mixed in their ores in open 

 furnaces; they are therefore distiUcd in retorts, which are ge- 

 nerally made of iron. Distillation is employed in this country 

 tor obtaining zinc, and abroad also for this metal and in the 

 mines of mei'cury. 



The mode of extracting the precious metals most in use in 

 Hungary and other parts of Germany, as well as in all the 

 American mines, is that of amalgamation of the ores with 

 mercury. By this process the gold or silver is dissolved by 

 the mercury and separated from the earthy nnxture, and also 

 from the baser metals which do not so readily combine with 

 the mercury. This jirocess recjuires however that the ores 

 should bo previously calcined to decompose the sulphurets, 

 and an addition of common salt is added to facilitate this de- 

 composition ; the whole is then finely powdered, and triturated 

 in water with the mercury by machines. Subsequent distil- 

 lation separates and preserves the mercury, and the gold or 

 silver is refined in the usual way. 



This 



