EECEIS'T COPPEE-EXTEACTITfa PEOCESSES. 139 



instead of scrap. The precipitation of one ton of copper takes 

 about 13 cwt. of metallic iron, so that it is a very important item, a 

 large proportion of the copper solution being dichloride. The bath 

 of chloride of iron may of course be made by dissolving the 

 metal in hydrochloric acid ; the apparatus in which the operation 

 is performed must be of wood, and no metal must be exposed to 

 the action of the chemicals. The bath is prepared by dissolving 

 120 lbs. of salt, or 112 lbs. of dry chloride of calcium, with 280 

 lbs. of green copperas (sulphate of iron) in 100 imperial gallons 

 of water ; 200 lbs. of sea salt are then added ; this quantity is 

 capable of chlorodizing and dissolving about 90 lbs. weight of 

 copper. 



In case the ores contain gold or silver, the latter will be taken 

 up by the copper solution, and can be recovered by digesting 

 with metallic copper, while the gold remains in the tailings, which, 

 being freed from copper, is in a condition admitting its easy 

 extraction. 



This process in the main is by no means . new, though the 

 original scheme of Bobert Oxland has been greatly improved 

 upon, and Messrs. Hunt and Douglas may be said to have given 

 it a commercial value. In April, 1868, Oxland took out his 

 patent for the extraction of copper from its ores by the use of 

 ferric chloride, or chlorhydric acid. At home the latter was a 

 waste product in the manufacture of salt cake, so that its use 

 was less costly than the employment of salt. The precipitation 

 was effected with metallic iron, and the bath was regenerated 

 for the extraction of further quantities of copper. By the patent, 

 however, it appears that after the first lixiviation Oxland dried 

 the ore in a furnace, and subjected it to a second treatment, 

 whereas Hunt and Douglas extract the copper in one operation, 

 leaving only half per cent, in the tailings. Besides, the chemicals 

 can be transported any distance in a solid form, which is no 

 mean advantage, and the precious metals extracted at very small 

 cost, while the whole of the reactions have been exhaustively 

 studied by the inventors. 



Stephen H. Emmens's Peocess 



was patented on 16th ^uly, 1875, its object being the economical 

 extraction of all the valuable metals, besides copper, which may 

 be associated with the ore under treatment. It consists essen- 

 tially of three stages : — 



1st. Boasting with or without salt to oxidize or chloridize the ore. 



2nd. Lixiviating with water acid, or brine, to wash out the 

 soluble metals. 



3rd. Precipitating the dissolved metals from solution. 



In the first stage he adds fluor spar ; in the second or lixiviat- 

 ing stage he adds salt or saltpetre, and sufficient sulphuric acid 

 to evolve enough hydrochloric or nitric acid to dissolve any 



