Mr. J. Napier on Copper Smelting, 



37 



sation of the fumes from these furnaces. A sample of this dried 

 stuff from a culvert we have found to be composed of — 



Silica . . . 

 Alumina . . 

 Lime . . . 

 Peroxide of iron 

 Oxide of copper 

 Oxide of antimony 

 Oxide of tin . 

 Arsenic . . . 

 Sulphuric acid 

 Soda . . . 

 Water . . . 



20-4 

 11-5 



2-8 



8-0 

 10-3 



7-7 



1-0 



•8 



21-5 



8-7 



6-8 



The powder left in the tanks is washed by allowing clean 

 water to pass through it for a time, it is then removed into a 

 heap ready to be calcined. 



The reactions taking place during these operations, we think, 

 are as follows : — The sulphate of soda is reduced by the coal to 

 the caustic state, some of it probably to the metallic condition. 

 Two samples of different qualities taken before being put into the 

 tank of water gave — 



Copper 32-3 28-6 



Iron 31-8 38*7 



Sulphur 26-7 26-5 



Silica 1*5 -5 



Antimony, &c '9 '7 



Carbonaceous matter .... '4 -6 



Sulphate and caustic soda, and loss 6*4 4*4 



100-0 



100-0 



When a piece of this coarse metal, after being fused with soda 

 and cooled, is immersed in water, there is a rapid absorption of 

 water with evolution of heat, and diffusion of a smell of sulphide 

 of hydrogen, while the mass falls into powder. Immediately 

 after this absorption, and before disintegrating, the piece of 

 coarse metal when broken has a brown colour, which, when seen 

 through a lens, is found to be caused by a reduction of the copper 

 either to the state of metal or suboxide, probably from the presence 

 of sodium, which decomposes the water, becoming converted into 

 soda, while the hydrogen reduces the subsulphuret of copper. 

 The powder soon turns black by exposure, and now contains 

 oxide of copper and oxide of iron along with the sulphurets. 

 The soda in the alkaline water in the tanks is in the caustic state, 

 with a little undecomposed sulphate, and contains antimony 



