RECENT COPPER-EXTEACTING PEOCESSES. 143 



for calcic chloride. To the writer it has suggested itself that the 

 use of any chloride may be dispensed with altogether, by simply 

 passing the charge direct from the roasting furnace into water, 

 when any sulphates that may have formed will be immediately 

 dissolved, and after being thoroughly washed the charge would 

 be ready for the ammonia, the solution of sulphates would be 

 recovered in the usual way, and less ammonia would be required 

 for the process. In fact, the larger the quantity of sulphates 

 formed the cheaper the entire process, irrespective of the saving 

 of chlorides in any form. 



Other Processes. 



In addition to the different processes above referred to, there 

 are several others possessing a local value dependent upon certain 

 special circumstances. One of the most notable is the process 

 used at the Edgeley Hill works in England, where a very large 

 body of poor ore, containing something less than two per cent, 

 of copper, is crushed, and then treated with chlorhydric acid, 

 to dissolve out the copper, which is precipitated with scrap iron. 

 In this case the acid is a waste product, the ore very easily mined, 

 the cost of the labour moderate, and iron procurable at a low 

 rate. 



The method of treating the copper schists at Mansfield is 

 pretty generally known, but it may not be out of place to advert 

 cursorily to it here. The ores contain from 1 to 4 per cent, of 

 copper, existing in a bituminous schist ; this schist is roasted in 

 heaps, and after combustion being first communicated the bitu- 

 men present sustains it for a considerable time. It is then placed 

 in a cupola blast furnace with coke. Matts and slags continually 

 flow from the furnace, the former of which are again roasted, 

 and again put back in the furnace. Repeated roastings convert 

 some of the copper sulphides into sulphates, which are repeatedly 

 lixiviated to separate the soluble sulphates. When any of the 

 ore contains silver, it will come out with the copper ; to extract 

 it a quantity of lead is added to the black copper, and the alloy 

 slowly heated in a furnace, when the lead will separate from 

 the copper, and be found to contain nearly all the silver present ; 

 the proportions for effecting the liquidation are about one-fourth 

 copper and three-fourths lead. Some lead will remain with the 

 copper, which is subjected to a stronger heat, in a suitable 

 apparatus, by which the whole of it is sweated out, the copper 

 cakes remaining in a porous state, and being subsequently refined. 



Eemarks. 



The study of the subject has convinced me that, where the 

 extraction of the copper is the sole consideration in cases where 

 the quality is pretty good, there is no process of reduction more 



p 



