Mr. J. Napier on Copper Smelting. 491 



Copper .... 99-80 



Iron -05 



Antimony , . . '04 



99-89 



While copper of the following composition, but without sound, 

 was received with every confidence : — 



Copper .... 98-90 



Iron '07 



Oxygen and loss . 1*03 



100-00 



That the poling has no influence on this phsenomenon has 

 been proved by trials made at all stages of that operation. 



Pure copper dissolves much more freely in strong nitric acid 

 than impure copper, and gives an immediate clear dark blue 

 solution. Most alloys impart to the solution a greenish tint ; 

 a small portion of silver, quite an olive-green ; indeed different 

 alloys furnish characteristic tints. These remarks, however, only 

 refer to undiluted solutions ; dilution takes away the peculiarity 

 of hue ; and if antimony or bismuth be present, the dilute solu- 

 tion is slightly turbid, requiring several hours to clear. 



The purifying of copper from alloy during the operation of 

 refining has formed the subject of many experiments. In 

 general some substance has been added to the copper in fusion 

 to dispel or scorify the impure metal, such as would combine 

 with the alloy and form with it a volatile compound, as chlorides 

 to form a chloride of antimony ; or ground glass to form a sili- 

 cate of antimony, which would be removed as slag ; but none of 

 these experiments gave any hopes of successfully and profitably 

 removing the alloys. One great difiiculty to overcome in these 

 experiments is, that the matters added float on the melted metal, 

 and consequently can only affect the surface. The oxide of one 

 metal may scorify or oxidize another metal when present in 

 copper, but this would only be a change of alloy, which in some 

 cases may be done to advantage ; thus the addition of a little 

 oxide of lead will greatly aid in purifying copper from antimony 

 and bismuth. 



That silica has an attraction for antimony, and will extract 

 it from copper, we have had suflicient evidence in its being accu- 

 mulated in the sand-bottoms of the refining furnace. A refining- 

 furnace used for copper containing small quantities of antimony 

 will soon become so deteriorated that metal of good quality can- 

 not be made in it. A refining-furnace bottom which had been 

 used for several months for ordinary cake copper, not containing 



3K2 



