COPPER 



921 



Fig. 510 is a longitudinal section of tho melting furnace ; fig. oil the ground plan, 

 in which a is tho fire-door; b, the grate ; c, tho fire-bridge ; d, tho chimney ; e, the 



509 510 



M 



511 



side openings ; /, tho working door ; g, the raking-out hole ; h, iron spouts, -which 

 conduct the melted metal into pits filled with water. 



The melting furnace is altogether 

 smaller, but its firing hearth is con- 

 siderably larger than in the roasting 

 furnace. The long axis of the oval 

 hearth is 14 feet; its short axis 10 

 feet ; its mean height 2 feet. 



Napier's Process for smelting Copper 

 Ores. As the copper ores of this 

 country often contain small portions 

 of other metals, such as tin, antimony, 

 arsenic, &c. which are found to deterio- 

 rate the copper, Mr. Napier's process 

 had in view to remove these metals, 

 and at the same time to shorten the 

 operations of the smelting process. 



The first two operations, that of 

 calcining and fusing the ore, are the 

 same as the ordinary processes ; but the 

 product of this last fusion viz., the coarse-metal is again fused with a little 

 sulphate of soda and coal mixed ; and whenever this becomes solid, after tapping 

 the furnace, it is thrown into a pit of water, where it immediately falls into an im- 

 palpable powder; the water boils, and then contains caustic soda and sulphide of 

 sodium, dissolving from the powder those metals that deteriorate the copper ; the 

 ley is let off, and the powder washed by allowing water to run through it. The 

 powder is then put into a calcining furnace, and calcined until all sulphur is 

 driven off, which is easily effected from the finely-divided state of the mass. This 

 calcined powder is now removed to a fusing furnace, and mixed with ores containing 

 no sulphur, such as carbonates and oxides, and a little ground coal, and the whole 

 fused ; the result of this fusion is metallic copper and sharp-slag that is, a scoria 

 containing much protosilicate of iron, which is used as a flux in the first fusion of tho 

 calcined ore, so that any small trace of copper which the slag may contain is thus 

 recovered. 



The copper got from this fusion is refined in the ordinary way, and is very pure. 



This process, which was patented in 1846, and carried on for some few years at 

 Loughor, near Swansea, has been found in practice to be incapable of completely 

 separating antimony, arsenic, and tin from copper, and has in consequence been 

 abandoned. 



When the copper ores contain tin to the extent of from J- per cent, to 2 per cent., 

 which many of them are found to do, Mr. Napier proposed to extract this tin, and 

 make it valuable by a process which has also been tho subject of a patent. The ore 

 is first ground and calcined, till the amount of sulphur is a little under one-fourth of 

 the copper present ; the ore is then fused with a little coal. The result of this fusion, 

 besides the scoria, is a reguius composed of sulphur, copper, and iron, and under this 

 is a coarse alloy of copper, tin, and iron. This alloy is ground fine, and calcined to 

 oxidise the metals, which are then fused in an iron pot with caustic soda, which 

 combines with tho tin and leaves the copper. The oxide of copper is now fused with 

 tho reguius. The stannate of soda is dissolved in water, and the tin precipitated by 



