Recovery of Copper from its Solution in Mine Drainage. 303 



mines, Co. Wicklow, where Dr. Henry Kenroy, when describing 

 the waters in 1751, states that the process was discovered there 

 by a shovel which had been left for some time in the mine water 

 being turned into copper. Mr. Matthew Johnston, one of the pro- 

 prietors of the mine, then proposed recovering the copper from 

 the mine water by this method.* 



The plan adopted by him was the following, which is interesting, 

 as being the first method used in this country.} 



The drainage of the mines was run into a chain of oblong pits, 

 each ten feet Jong, four wide, and eight deep, the bottoms of which 

 were laid with smooth flags and the sides built up with stones 

 and lime with rude wooden beams across the pits to lay the iron 

 bars on. The copper replaced the iron, which passed off in solu- 

 tion; to hasten this reaction, the iron bars were frequently taken 

 up and the copper rubbed off into the pit; in about twelve months 

 the whole bar was dissolved if the iron was soft; but hard iron or 

 steel were acted on less quickly and therefore were not found to 

 answer so well. When the iron was all dissolved the water was 

 turned off the pit, and the copper shovelled out ; this red copper 

 mud was laid in heaps and when dry became a reddish dust. One 

 ton of iron produced one ton nineteen and a-half cwt. of this 

 copper, and each ton of which produced sixteen cwt. of pure 

 copper ; that is to say, one ton of iron was sufficient to produce one 

 ton eleven and a-half cwt. of copper, which was worth £10 more 

 per ton than the copper smelted from the ore. 



It was subsequently found advantageous to run the drainage 

 into settling pits, and to pass only the clear waters over the irons. 

 Evidently only a small quantity of the copper in solution was 

 saved, as it appeared that the pits might be continued as far fis 

 the workers pleased ; for the waters did not sensibly abate in 

 quality by being subjected to the process. The quantity of copper 

 running waste about this time must have been enormous, as in 



* Price (Mineralogia Cornubiensis (1778) p. 291^, gives the credit of its adoption here 

 to some Cornish miners who, having emigrated from Chacewater, settled at Cronebane, 

 and adds, " Captain Thomas Butler, who was one of Eedruth, and manager of that mine 

 (Cronebane), persuaded the proprietors to adopt the scheme of precipitating copper." 



t The following account is compiled from Dr. Kenroy 's paper in the Philosophical 

 Transactions for 1751. There appears to be some inaccuracy in the statement of the 

 quantity of precipitated cnpper produced. Compare page 317, and No. XXVI., Table A. 



SciEN, Peoo. R.D.S., Vol. hi., Pt. vi. 2 B 2 



