Mr. J. Napier on Copper Smelting. 455 



solve 32 grains of metallic copper in vitriol^ it would require 49 

 grains of the strongest acid, and nothing less ; hence 33 and 49 

 are their relative combining proportions. The same law holds 

 good for every substance combining whether by fusion or solu- 

 tion. The equivalent or combining proportion of silica is 46. 

 In order, then, to form a compound with silica that will be 

 easily fused, we must employ equivalents of other substances. 

 The following is a table of the combining proportions of those 

 matters found in copper ores, or added as flux to fuse silica : — 



Silica 46 



Slaked lime 37 



Carbonate of lime, chalk, shells, &c. . 50 



Fluoi'-spar 39 



Carbonate of barytes 98 



Carbonate of magnesia 34 



Carbonate of soda 53 



Carbonate of potash 69 



Protoxide of iron 36 



Peroxide of iron 40 



Oxide of copper 40 



Oxide of lead 112 



Oxide of tin 67 



^Vith these proportions, and an approximate analysis of the 

 mixture of ores, a pretty accurate idea may be formed, before the 

 matters are put into the furnace, of the kind of scorise that will 

 be formed. 



For the general character of the ores we refer to the tables in the 

 first article, where it will be observed that silica is the principal 

 earth present. Le Play gives the average composition of all the 

 ores smelted in a work for a length of time as follows : — 



Silica 38-5 



Alumina 2'4 



Lime '3 



Magnesia "4 



Copper 13"5 



Iron 19-7 



Other metals "9 



Sulphur 23-1 



Oxygen, carbonic acid, and water 1"2 



1000 



The composition of the slag or scoria; from fusing these ores 

 is given by the same author as follows : — 



