Mr. J. Napier on Copper Smelting* 



351 



The reactions which occur in the process of roasting are the 

 same. The oxygen of the air combines in the first place with a 

 portion of the sulphur, forming sulphurous acid. A portion of 

 the copper is also oxidized, and instantly reacts upon another 

 portion of the subsulphuret, reducing the metal, as shown above. 

 The process is a very beautiful one, and exhibits a nice adapta- 

 tion of principles to practice. The sponge regulus has a specific 

 gravity of 5, the reduced copper about 8 ; so that the copper 

 sinks to the bottom where it is protected, and a new surface of 

 regulus becomes exposed to the action of the air. 



If the ore was pure, or if no select copper is required, the 

 operation of roasting is continued until the whole of the copper 

 is reduced, when it is tapped out into sand-moulds, forming 

 coarse copper, bed copper, pimpled copper, or blistered copper, 

 according to quality. The term coarse copper is applied occa- 

 sionally to all these kinds except the blistered. If the ingot sets 

 with contraction with a smooth hollow surface, it is termed 

 bed, and generally indicates the presence of other metals, as tin. 

 When the surface of the ingot is covered with pimples, it is 

 termed pimpled copper, and indicates the presence of sulphur. 

 When covered with large scales or blisters of oxide of copper, it 

 is termed blistered; this only takes place when the copper is good 

 and ready for refining. The following analyses of several of these 

 kinds will illustrate our remarks : — 



All of these contained suboxide of copper dissolved in the 

 metallic copper. 



When the regulus contains other metals, such as tin, anti- 

 mony, &c., the first portion of copper reduced reacts upon the 

 sulphurets of these metals, reducing them, and the copper passes 

 again into sulphuret ; hence the first portion of reduced metal 

 will contain the foreign metals. When making select copper, 

 the roasting is carried on until about one-fourth of the copper 

 in the regulus is reduced ; the furnace is then tapped, and the 

 reduced metal is obtained at the bottom of the first and second 

 ingots or pigs, as copper bottoms which contain most of the me- 

 taflic impurities. The regulus is Collected and again roasted 



