tlecovery of Cop'per from its Solution in Mine Drainage. SOO 



much of the iron in solution separates, as ochre,* and may be removed 

 by allowing it todeposit in large settling ponds. On passingthe clear 

 water from these ponds through another series of highly inclined 

 precipitating launders, clean copper will be deposited. By pro- 

 ceeding in this manner, not only may the waters be exhausted of 

 the contained copper, but large quantities of ochre extracted and 

 -saved. 



It has been often observed that the longer the precipitated 

 copper is allowed to remain on the iron, the purer it becomes, 

 and it is only a question of time to convert the loose granular 

 precipitate into a sheet of malleable copper, that protects the iron 

 to a great extent ; before this is accomplished a dense crystalline 

 deposit of copper, of great purity, is produced. The most favour- 

 able time for detaching the precipitate appears to be when this 

 stage in the process has been reached — this is usually from thirty, 

 five to fifty-five hours in tolerably strong water, after the metals 

 have been put in. It seems, therefore, that about once in forty- 

 eight hours would be sufficiently often for cleaning the metals, as 

 then the precipitate would be in a granular crystalline state, not 

 coherent enough to resist disintegration. 



Sudden floods, and specially those after warm iveather are 

 usually very rich in copper salts, and there is often considerable 

 difficulty in dealing with them so as to save all the copper. For 

 this purpose tin clippings, specially those having the coating of 

 tin removed, are admirably adapted ; they are let into the launders 

 as the floods come down which, if rich, dissolve them in a very 

 short time. Spare launders might also be provided and kept 

 stocked, either with clippings or ordinary metals ; so that duiing 

 floods the waters could be turned on to them. 



Precipitation in other Districts. 

 Copper is now extracted from the drainage of almost all active 

 copper mines; in many mining districts the poor copper ores 

 are .treated at the mine by some wet process, as it has been found 

 that ores containing but 1^ per cent, of copper, will pay when 

 treated thus. However, in this country, these processes seem to 

 have been greatly neglected, and when the mine drainage has 

 been treated, the results as a rule have been poor (as may be seen 

 from the annexed table), as the attempts to improve these 



* This is probably due to the rea'^tion noted by Waguer vvhicli is mentioned on page 320- 



