170 Mr. Napier on Copper Sheatliing. 



furnace, and kept at a dull red heat for several hour?, which expels 

 a great quantity of the sulphur, and oxidates a portion of the iron. 

 It is then fused in a separate furnace, the silica and oxide of iron com- 

 bining forms scoria, or slag; the copper with iron and sulphur combines, 

 forming what I have described as regulus; the slag or scoria floats and 

 is skimmed off, the regulus is tapped into a deep pit of water which 

 granulates it. This granulated regulus is again subjected to calcining 

 and fusing, until the iron is mostly all oxydised, when the copper remains 

 as a sub-sulphuret, with a little iron and a portion of the impure metals. 

 This product is now roasted, by being put into a reverberatory furnace 

 furnished with air holes, and kept at a semi-fluid state, with a free cur- 

 rent of air passing over the surface. The reaction may be thus explained. 

 A portion of sulphur is carried off by the oxygen of the air, and the 

 copper is oxidated, and this oxide of copper instantly reacts upon or is 

 decomposed by another portion of sub-sulphuret, the copper of both being 

 reduced to the metallic state without any carbonaceous matter. Copper 

 in the fused state has a stronger attraction for sulphur than any of the 

 other metals, so that when copper begins to be reduced, it will first reduce 

 all the other sulphurets present, except iron. Therefore, by carrying on 

 this roasting until about the half of the copper is reduced, and then tap- 

 ping the furnace, this reduced portion will contain all, or mostly all, the 

 impurer metals which had existed in the regulus. The sub-sulphuret 

 remaining is selected and reduced by itself in a separate furnace, to 

 make pure or select copper for yellow metal. Thus the process of selecting 

 affected the whole copper trade, and particularly the sheathing, for the 

 yellow metal was not only a competing article with ordinary sheathing 

 but its production almost necessitated the deterioration of that against 

 which it was to compete. The reduced copper with the impurities was 

 taken and subjected to long roasting and refining; if the quality after 

 that would bear rolling it was used up for sheets, if not it was sold as tile. 



The copper ti-ade is now almost entirely relieved from these circum- 

 stances, by the abundant supply of Australian ores, which are mostly all 

 pure, giving copper of the best quality ; however, so far as regards the 

 past, and the question under discussion, these circumstances all tend to 

 show that the cause of the deterioration of sheathing is impurity in the 

 copper. 



The question now occurs, what are the impurities which have thus 

 deteriorated our copper so much ? The paucity of rigid analyses of copper, 

 and especially of that used for sheathing, prevents a positive answer being 

 given to this question; but of the few analyses which have been made 

 public, with one or two exceptions, it is remarkable that there is no men- 

 tion made of the presence of antimony, but often of tin, and in those 

 given by Mr. Prideaux, there are both zinc and tin. These analyses 

 were no doubt made with the-grcatest care, nevertheless we cannot help 

 thinking that the presence of this metal has been overlooked. Our 

 reasons for thinking so are, that antimony is an ingredient in almost all 



