138 EECENT COPPEE-EXTEACTIIfa PE0CESSE3. 



by a strong boy. "With only a moderate amount of instruction 

 any person of average intelligence, and without any previous 

 metallurgic knowledge, may conduct tlie process, even on a large 

 scale. It derives its name from tlie Snowdon Mountains, wliere 

 it is at present being successfully employed, and where, probably, 

 no other known process would be available. 



The Hunt and Douglas Pkocess 



is rapidly and deservedly gaining favour. It possesses several 

 features that give it special claims to consideration. The appa- 

 ratus used is simple and inexpensive ; the treatment capable of 

 being easily taught to an intelligent workman ; the materials 

 used in the extraction of the copper from its ores cost but little in 

 the first place, and are capable of doing an indefinite amount of 

 duty, with but little addition to supply inevitable waste ; the 

 precipitant is usually scrap iron, which, however, may be replaced 

 with iron sponge. 



In case the ore contains sulphur or arsenic, it is crushed, passed 

 through a sieve of forty holes to the linear inch, and calcined. 

 At the Ore Knob Mine in America the cost of the wood used in 

 desulphurizing is found to be only one shilling for every ton of 

 ore treated. The calcined ore is then treated with a solution of 

 sulphate of iron and salt, of a certain strength, which experiment 

 has found to be most effective ; these are kept stirred in circular 

 tanks, at a temperature of about 180 degrees Fahrenheit ; the 

 stirrers make about twenty-five revolutions, and the extraction 

 of the copper occupies about eight hours. It is then allowed to 

 settle, the clear part drawn off, and the turbid led into a settling- 

 vat. The copper is precipitated from a hot solution by scrap 

 iron ; the precipitation occupies twentj^-four hours. 



The rationale of the process is as follows : — Sulphate of iron 

 and salt being dissolved and mixed together mutually decom- 

 pose, forming sulphate of soda and chloride of iron ; on the 

 addition of ore containing oxide of or carbonate of copper (or- 

 the desulphurized ore), the chloride of iron reacts upon the 

 copper, forming chloride of copper and dichloride, and precipi- 

 tating the iron. In subsequently passing the solution containing 

 these chlorides of copper over metallic iron, the copper then 

 changes place with the iron, the former being precipitated as 

 cement copper, and the regenerated chloride of iron solution 

 being returned to the bath to act on successive charges of ore. 



It will be seen that the cost of treatment is particularly small, 

 but it may be added that the loss in treatment is less than half 

 per cent., while the material employed in the extraction of the 

 copper does duty many times. The one great source of expense, 

 especially in situations far removed from the sea coast, is the 

 iron used in precipitating ;• but in places where hematite is 

 abundant they are commencing to make sponge iron to use 



