Mr. J. Napier on Copper Smelting, 



33 



the former articles. The coarse metal obtained by this fusion 

 varies considerably in quantity and also in composition, depend- 

 ing upon the length of calcination, the quantity of iron and sul- 

 phur remaining, the heat of the furnace, &c. It is also liable 

 to be affected by the flux when any is used. If that be fluor- 

 spar or lime, the coarse metal will be enriched ; but if oxide of 

 iron, which nevertheless is a preferable flux, the coarse metal 

 will not be so rich in copper, a portion of the oxide of iron being 

 reduced to the state of sulphuret. The qualities of oxide of iron 

 used are the rich slags from iron cupola furnaces, and the scale and 

 pickling dust obtained from the iron plates in tin-plate works, 

 their composition being as under : — 



Slag. Pickle dust. Rolling scale* 



Silica 25 4-0 6*4 



Protoxide of iron ... 75 95-5 93-6 



. Carbonaceous matters .... '5 



100 



100-0 



100-0 



The following table of analyses of a few kinds of coarse metal 

 will show its variable character : — 



Most of these contained small portions of other metals, and 

 silica, which are not given. From the varying character of the 

 mat, it is impossible to reduce its composition to any chemical 

 formula ; we think, however, that the copper and sulphur, after 

 fusion, always exist as a subsulphuret ; and the inconstancy in 

 the composition of the coarse metal is in the relations of the 

 sulphur and iron ranging from a bisulphuret to a protosulphuret, 

 or more probably mixtures of these. 



M. Le Play gives as the composition of the coarse metal, — 



Copper . . . , 

 Iron . . . . 

 Sulphur . . 

 Other metals, &c. 



33-7 



33-6 



29-2 



31 



"99^ 



and deduces from this the formula 3Cu2SFe2S^ + 4FeS, which 

 Phil Mag. S. 4. Vol. 5. No. 29. Jan, 1853. D 



