1865.] MACFARLANE— EXRACTION OP COPPER. 223 



From this it appeared that in the residue there were present of 

 copper — 



la an insoluble state...* 11.82 grs. = 25.15 per cent. 

 In a soluble state 10.51 " =22.36 " 



22.33 grs. 

 Amount of copper lost .. 24.67 " =52.49 



47.00 grs. 



The only way in which this extraordinary loss of 52.49 per cent, 

 can be accounted for, is by supposing it to have been volatilized; 

 and other circumstances confirm this view. The calcined sub- 

 stances contained 66.35 grains of sulphate of soda. Consequently 

 53.11 grains of common salt must have been decomposed, and 

 32.08 grains of chlorine liberated from it. Of this, 11.82 grains 

 are found in combination with the copper in a soluble state. The 

 remaining 20.26 grains were more than sufficient to form sub-chlo- 

 ride with the 24.67 grains of copper volatilized. The whole of the 

 32.08 grains of chlorine were not however sufficient to convert the 

 forty-seven grains of copper contained in the ore into soluble proto- 

 ehloride. 



From this experiment it became evident, 1st, that even with 

 the use of a large quantity of peroxide of iron, it is difficult to treat 

 copper pyrites so as to produce enough of sulphuric acid to render 

 all the copper soluble ; and 2nd, the calcination must be per- 

 formed at as low a temperature as possible, in order to prevent the 

 volatilization of the copper. The experiment was therefore per- 

 formed a second time, care being taken to keep the temperature 

 low. The same materials, in the same proportions, were used, and 

 the product this time from the 800 grains weighed 792 grains, 

 and contained — 



Iron oxide and other insoluble matter.. 66.00 



Sulphate of soda 17.60 



Chloride of copper 9.64 = 4.55 copper. 



Chloride of sodium (by difference) 6.76 



100.00 



Thirty-six grains of copper out of the original forty-seven were 

 this time removed in a soluble form ; equalling seventy-six per cent 

 instead of the twenty-two per cent, of the former experiment. Fur- 

 ther, it appears that 139 grains of sulphate of soda were formed ; 

 and consequently 111 of chloride of sodium decomposed, and sixty- 



