Mr. J. Napier on Copper Smelting, 



177 



During the last twelve hours the heat of the furnace was at a 

 bright yellow^ sufficient to fuse uncalcined coarse metal. 



The following is a repetition of the same experiments with 

 another charge of powder, the heat of the furnace being more 

 intense than the last : — 



By casting the eye along the sulphur and sulphuric acid 

 columns, the change taking place is very apparent and interest- 

 ing. The rapidity of the formation of sulphuric acid at the 

 commencement may be assisted by the powder being damp; 

 nevertheless there seems to be an intermitting action between the 

 sulphur as sulphurets and sulphuric acid, the oxide of iron pro- 

 bably playing a part in these reactions. It is also seen that it is 

 much more difficult to decompose sulphate of copper by heat than 

 sulphate of iron. It is remarkable how little sulphur is driven 

 off while in the top bed, and how rapidly it is evolved when the 

 powder enters the lower and hotter bed, so as in a few hours to 

 decompose the whole of the sulphurets. 



ThefoUowing table contains the results of experiments madewith 

 a three-bed calciner, the heat passing from one bed over the other, 

 the powder being put in at the top and let down through each 



