464 Mr. J. Napier on Copper Smelting. 



room for another, and so forth. This law must be attended to 

 in all subliming operations to be successful. 



Several plans have been proposed for conducting the fumes of 

 the ordinary caleiner into chambers or other apparatus, in order 

 to collect the sulphur, arsenic, &c. that may sublime during the 

 process of calcination. The long culverts which are generally in 

 use effect this object to a great extent; and to render these more 

 effective, some smellers have apparatus for causiug water to be 

 constantly trickling down them, so that the sulphur and metallic 

 fumes passing through the water are mostly all condensed. Many 

 tons' weight is deposited in the ordinary culverts during the year, 

 which is collected from time to time, and all that is valuable 

 extracted. A quantity of stuff from a culvert leading from ore 

 calcining furnaces alone gave by analysis — 



99-9 



The water was not originally in combination, but had been 

 added to prevent dust. 



I\Iany other plans have been proposed and patented for the 

 saving of the sulphur that is at present allowed to escape into the 

 atmosphere. Some purpose converting it into sulphuric acid, as a 

 marketable material in connexion with the calcination ; others to 

 roast the ore in kilns, like those forburning lime, and condense the 

 fumes, &c. : all have their merits as inventions. Any process of 

 this sort to be useful must not interfere with the time of obtaining 

 the copper, it being so much more valuable than any other ingre- 

 dient in the ore. And no process can be adopted by the smelters 

 that will take away all the sulphur, without at the same time 

 requiring a new method of smelting ; for according to the present 

 method, a certain amount of sulphur is essential to the purifying 

 and obtaining the metal. Some of the plans might do well 

 to work by themselves at the mines, taking care to leave as much 

 sulphur in the ore as would form a coarse metal of 30 per cent, 

 copper after fusion. The greater portion of the arsenic, and an 

 average of half the sulphur the ores contain, might thus be 



