Mr. J. Napier on Copper Smelting. 461 



After 20 hours a half per cent, of copper as sulphate, no iron. 



After 24 hours nearly the same. 



After 28 hours a mere trace of acid and copper, no iron. 



After 32 hours a mere trace of acid and copper, no iron. 



After 36 hours trace of acid, no metal. 



After 40 hours no trace of acid or metal. 



After 44 hours no trace of acid or metal. 



Several other experiments were tried of a like kind with similar 

 results, to which we may have recur to in connexion with others 

 of a different description in order to arrive at the causes of these 

 reactions in a calciner. 



For the purpose of saving time and fuel a compound calciner 

 has been tried, and we believe is still in use in some works 

 where one bed or hearth is placed over the other. The ore is put 

 into the top bed, then passes through holes in the floor to the 

 second or middle, and then to the third or lower bed, where it 

 receives the highest heat ; so that nine hours' calcination is equal 

 to three hours iu each bed. The first experiments made with 

 this sort of calcmer had for their object to ascertain the length 

 of time required to calcine dead. The ore was tested for sulphur 

 every four hours, allowing sixteen hours in each bed ; each sample 

 was also boiled in water, and the sulphuric acid determined. 



The two following tables contain the residts of experiments 

 made with ores calcined only for a short time, the whole ingre- 

 dients of the ore being taken in testing. 



Table I. — A mixture of ores not analysed before being put into 

 the furnace. 



ICopper 12-4 12-0 12-4 12-4 l-'l 



[iron 26-3 263 25-51 25-2, 24 



i „i 



Silica I 31-9. 30-8J 26-51 2911 306 



Sulphur ...I 26-8, 28-3| 34-4| 30-4! 28- 1 

 |Sulphuric 1 

 acid ... J 



•1 •! trace 



12-0 

 24-9 

 28-6 

 2S-7 



12-5 11-3 11-7 

 25-0 25-2 27-5 



30-8 

 27-4 



Itrace 



28-3 

 28-9 



305 

 24-0 



2S 



13-5 

 27-5 

 316 

 14-7 



132 

 275 

 33-2 

 18-4 



•1 



