1847.] Improvement in Smelting Copper Ores. 107 



effect of weak electrical currents on copper ores; and the follow- 

 ing is an account of the results at which they had arrived before 

 taking out their patent. The process consists of two operations, 

 viz: roasting the ore, and the precipitation of the copper. The 

 roasting is effected in a reverberatory furnace, either by conver- 

 sion of the sulphuret into sulphate by the action of the air, or in 

 the transformation of the oxide of copper into sulphate, by cal- 

 cining it with sulphate of iron, at a dull red heat in a current of 

 air, the iron being left in a state of peroxide. Washing, then, 

 extracts the sidphate of copper, so that the most impure minerals 

 will afford copper equally pure with the carbonate or oxides. In 

 the precipitation by galvanism, batteries would be far too costly; 

 and they have obtained the same results without the use of exte- 

 rior batteries. The principle is as follows: If two solutions are 

 placed one over the other, one of sulphate of copper, very dense, 

 and the other sulphate of iron less dense, and in the first is placed 

 a plate of metal, and in the second, a fragment of cast iron, and 

 then unite these two metals by a conductor, the precipitation of 

 copper commences at once, and is completed in a long or short 

 period, according to the temperature, the concentration of the 

 liquids, and the extent of metallic surfaces, the state of the copper 

 becomes greatly changed as the liquor becomes weaker. To ob- 

 viate this, they take advantage of the following phenomena; after 

 some minutes' action, there exists four strata in the liquids; at the 

 bottom is a dense solution of sulphate of copper, then a less dense 

 solution of the same salt; next, a sulphate of iron, and on the 

 surface a less dense solution of the same. If, therefore, we ar- 

 range at the level of each of these liquids suitable apertures for 

 the addition or the removal of the liquid, they can be kept at a 

 uniform state of density, and thus the copper is always pure, and 

 in the same physical condition. 



For convenience, the liquids are now arranged in vertical, in- 

 stead of horizontal layers; they are now to be separated by a dia- 

 phragm very permeable to electricity, but not to liquids, paste- 

 board answers perfectly well for this, and lasts for months. The 

 apparatus is then arranged as follows: a chest of wood, lined 

 \vith lead or some suitable mastic, contains the solution of sulphate 

 of iron; into this chest a number of cases are plunged, made of 

 a frame having its ends and bottoms formed of iron plates coated 

 with lead, the sides being of pasteboard. The strong solution of 

 sulphate of copper enters through a pipe near the bottom, and 

 escapes in its weak state through an opening at the top; in each 

 case is placed a sheet of leaded iron, and between each are plates 

 of cast iron; separate rods connect each plate with the common 

 conductor, which is supported over the apparatus, and the copper 

 is precipitated on both sides of the sheet of metal, the pasteboard 



