346 Mr. J. Napier on Copper Smelting, 



slag, from its containing an excess of oxide of iron, and being 

 consequently used as a flux for fusing the ore. 



The blue metal varies considerably in composition, according 

 to the state of the calcination of the coarse metal. The following 

 analyses of several kinds will make this variation manifest: — 



Low Average Good Superior 



quality. quality. quality. quality. 



Copper .... 55 588 632 65-8 



Sulphur .... 23 205 21-8 226 



Iron 18 11-6 8-6 9*1 



Silica 3 4-2 4*8 1-8 



Antimony, tin, &c. 1 1*3 'S *7 



Oxygen and loss . ... 3*6 '8 



loo 1000 1000 1000 



Com])aring the results of this table with the quantity of sulphur 

 in the calcined coarse metal, some sulphur appears to have been 

 evolved during the fusion, but the quantity given off is very 

 small. The reason of the blue metal being so rich in copper is 

 owing to the rich slags added before fusing, which contain no 

 sulphur. 



Blue metal is often full of small specks of reduced copper, and 

 small cavities lined with fine fibrous metallic copper, growing 

 out like moss ; these fibres are often not less than an inch in 

 length. This is appropriately termed copper moss; it occurs 

 generally where the metal has come into contact with moisture, 

 which probably not only produces the cavities, but effects the 

 reduction of the metal. The composition of this moss given by 

 Le Play is — 



Copper 98-2 



Iron '4 



Nickel -6 



Mixed carbonaceous matters . '2 



99-4 



It has sometimes a brassy appearance, and at other times ^ 

 crimson-red tint. A sample of each gave by analysis — 



Brass colour. Red coloui*. 

 Copper .... 98-5 99*0 



Sulphur .... -4 -4 



Tin, antimony, &c. 1*0 '5 



Iron trace trace 



^9^~ 99¥ 



The purity of the copper ii remarkable at this stage of th^ 



