[ 453 ] 



LXXIII. On Copper Smelting. By James Napier, F.C.S* 

 [Continued from p. 355.] 

 • Calcination of the Ores. 



'X'HE arrangiDg and classifying the ores when brought into 

 J- the smelting-works is a most important operation, affect- 

 ing the whole after-workings, both as regards the cost and qua- 

 lity of the copper. The mines and localities from which the ore 

 is brought are so numci-ous, that it would be impracticable to have 

 a separate yard or compartment in the smelting-works for every 

 one; hence a more general classification is adopted, such as 

 highly sulphurous ores, including those containing mundic, flue- 

 can or clayey ores coloured red or yellow, gray sidphur ores, &c. 

 Sometimes certain mines or localities are known to produce ores 

 of a certain quality ; for instance those from Hayle have generally 

 the character of being 5/(^' (difficult to fuse) ; those fromFoey Con- 

 sols, of making inferior copper, &c. ; these are all classified : then 

 there are compartments for Cuba and Cobre, for the Irish ore, 

 for Chilian ore, and for Australian ore ; besides these qualities^ 

 the per-centage of copper in the ore has also to be considered : 

 two or three lots of ores having respectively 7, 8, or 9 per cent, 

 of copper, if their other qualities agree, may be put together, but 

 not ores having 4, 8, and 12 per cent. The object of these 

 arrangements and classifications of ores in the yard is to enable 

 the o])erative smelter to select from and make up a constant 

 working mixture, having the following characters :— 

 1st. That the copper in the mixture be not under 9 nor above 

 13 per cent.; if under the former, it is unprofitably poor; if 

 over the latter, the slags have a tendency to contain copper, 

 creating a loss. 

 2nd. That after being calcined an ordinary time, it will fuse 

 easily without the necessity of adding flux, giving a clean and 

 easily fused slag. 

 3rd. That the mat or coarse metal obtained from fusion contain 



as near as possible 30 ])er cent, of copper. And 



4th. That the mixture do not contain ores having impurities 



calculated to make the copper of a lower quality than is desired. 



There is no definite or fixed rule to guide the smelter in these 



classifications except a practised eye in distinguishing the cha- 



racter of ores, and the report of the assayer. 



It must be borne in mind that we arc speaking of ores con- 

 taining sulphur ; for although carbonates and oxides arc brought 



* Communicatetl by the Author, ulio reserves to himself the convrieht 

 any infringement whereof will invoke legal proceedings.— Eds. ' • ^ ' 



