1865] MACFARLANE — EXTRACTION OF COPPER. 229 



If however we neglect the 8-8 grains copper contained in the 

 residue used, which it is perfectly reasonable to do, then 95*7 per 

 cent, of the copper in the ore is dissolved in water alone, and 

 the whole of it on the additional use of a slight quantity of dilute 

 sulphuric acid. One of the most striking facts deducible from the 

 results of this experiment is that 46*64 per cent of the sulphur con- 

 tained in the original ore was converted into sulphuric acid, and 

 then into sulphate of soda. The amount of chlorine liberated by the 

 formation of such a large quantity of this salt, must have been 

 greatly in excess of what was necessary to render the copper soluble. 



On account of this latter circumstance I attempted to reduce 

 the quantity of salt used, and made four calcinations in the propor- 

 tions of two parts of residue, one part of fresh ore, and one fourth 

 of a part of salt. The ingredients, used with their copper contents, 

 were as follows. 



1. 2. 3 & 4. 



GRS. GRS. GRS. 



Residue .2000 with 8-8 Cu 1500 with 6-6 Cu 2000 with 20 Cu 



Fresh ore 1000 "86-0 « 750 "64-5 « 1000 » 86 " 



Salt 250 " 175 " 250 « 



3250 with 94-8 Cu 2425 with 71 -1 Cu 3250 with 106 Cu 

 The products of these four experiments contained of copper 

 respectively : 



1. 2. 3. 4. 



GRS. GRS. GRS. GRS. 



Soluble in water 59-11 40-5 62-22 66*00 



Soluble in dilute S0 3 14-69 7-3 3-60 10-00 



Insoluble ?21-00$ 7 ' 3 18 ' 18 l1 ' 21 



Unaccounted for > \ 16-0 22-00 12-79 



94-8 71-1 106-00 106-00 



These results were by no means encouraging, yet the quantity 



of salt was quite sufficient for chloridizing the copper. One fact 



must however be mentioned with regard to these trials ; they 



were very diligently stirred during the calcination. 



No other resource was left but to return to experimenting with 

 a larger quantity of salt. Accordingly the following ingredients 

 were mixed and calcined : 



2950 grains residue of 1-0 per cent. = 29-5 grains copper. 

 1500 " fresh ore of 8-6 " =129-0 " 

 750 " salt 



5200 grains containing 158-5 grains copper. 



