1868.] MACFARLANE — EXTRACTION OF COPPER. 461 



and of peroxide, the solution from the first experiment gave more 

 than that from the second. 



The plan of using the chlorides of iron for the extraction of 

 copper is not proposed here for the first time, but the manner of 

 using it advantageously, as indicated by the above experiments, 

 differs essentially from those heretofore proposed. The above 

 experiments shew that direct calcination of a raw ore with the 

 re-agent, under unlimited access of air, seldom leads to a successful 

 or a reliable result. On the other hand, when the ore is pre- 

 viously calcined, the temperature kept low, and the current of 

 air excluded, the application of the chloride becomes advantageous 

 and practicable. 



In the above trials, and others which have not been mentioned, 

 the copper was sometimes determined volumetrically, and some- 

 times precipitated by iron and weighed. The residual solutions 

 from the latter operation were evaporated to dryness, and the 

 proto-chloride of iron recovered. The precipitated copper was 

 easily compressed, in a diamond mortar, into little solid cakes 

 readily fusible to buttons before the blow-pipe. 



This process of extracting copper would seem to be capable of 

 affording more reliable and more economical results than any 

 hitherto proposed. Any ores, whether rich or deficient in 

 sulphur, may be treated by it, except those containing carbonates 

 of lime or magnesia. The exclusion of air, and the low temperature 

 employed, render a decomposition or volatilization of the proto- 

 chloride of copper, when once it is formed, impossible. There 

 being no free acids in the solutions obtained, an equivalent quan- 

 tity only of metallic iron is consumed. By evaporating the 

 residual solutions, the re-agent is always recovered, and thus a 

 further saving is effected. The amount of copper contained in 

 the insoluble residues, is, in most cases, below, and never exceeds 

 that of copper furnace slags, while the cost of the process will not 

 exceed one-third of the expense of the ordinary method of produc- 

 ing copper from its ores by smelting. 



With regard to applying it on the large scale, there would appear 

 to be no grounds for anticipating any difficulty. The pulverisa- 

 tion of the ore would be most economically effected by wet stamps. 

 If allowed to drain thoroughly, after being thrown out of the 

 slime pits, it could then be completely dried and calcined, at the same 

 time, in reverberatory or other furnaces. The roof of these furnaces 

 might consist of cast iron plates which might form the hearths of 



