Recovery of Copper from its Solution in Mine Drainage. 31^ 



tracted) which was balled with small coal and furnaced forming 

 sodic sulphide ; this was dissolved out with water, and into the 

 solution a current of carbonic dioxide (obtained from the combus- 

 tion of coke) was passed, carbonate of soda was thus formed and 

 sulphuretted hydrogen given off (Gibhs). 



Sulphuretted hydrogen has also been prepared from barium 

 sulphide (Wagner.) 



Calcic sulphide has been proposed for precipitating the copper, 

 and was used in Escalle's process as worked near Marseilles, the 

 copper being present as chloride ; in a solution of sulphates, how- 

 ever, the precipitate would be largely contaminated with sulphate 

 of lime. For the same reason carbonate or hydrate of lime would 

 be objectional, especially as, unless the solution were very 

 pure, many other metals would be precipitated along with the 

 copper. 



At the Royal Works of Mlilden and Halsbriicke, near Friberg, 

 sulphuretted hydrogen is produced by the action of sulphuric 

 acid on sulphide of iron, the latter being prepared by roasting 

 together furnace clay and iron pyrites free from blende, the sul- 

 phate of iron formed being subsequently crystallized out. 



Several electrical methods have been proposed for the extrac- 

 tion of copper from its solutions. Becquerel (1835 — 1840) made 

 numerous trials, but their aim was more for saving the silver ; 

 in these, couples were formed of various combinations, the nega- 

 tive poles were immersed in porous diaphragms filled with salt 

 solution, which were immersed in the liquors, the other pole being 

 in direct contact with the liquid. 



Patera's method was for extracting the copper from poor cemen- 

 tation waters. In cells of clay or fir- wood were placed iron plates, 

 that were connected with small pieces of coke, which formed the 

 negative electrode, a salt solution being used to produce the action. 



Keith's method* consists in filling large porous cells (32 inches 

 high by 12 inches diameter), with a solution of sulphate of iron 

 (free from copper), and scrap-iron ; these cells are placed in large 

 barrels, through which the copper solution flows, in which a 

 copper plate is immersed that is connected with the cells externally 

 by a wire ; the copper is deposited on the plate in a pure and 



* See "Engineering and Mining Journal," 1877, page 366. 

 SciEN. Proc. R.D.S., Vol. hi., Pt. vi. 2 C 2 



