50 



166. Process of extracting copper, silver, and gold 

 from burnt pyrites. 



1876. Exhibited ~b\j the Widncs Metal Company. 



No. 1. Cupreous iron pyrites, employed in the manufacture 

 of sulphuric acid. 



Water 70 



Sulphur 49-00 



Arsenic '47 



Iron - 43'55 



Copper - - 3-20 



Zinc '35 



Lead '93 



Lime '10 



Siliceous residue '63 

 Oxygen, and traces of various metals - T07 



100-00 



No. 2. Burnt ore, or cinder remaining after the almost com- 

 plete elimination of the sulphur from the pyrites as sulphur 

 dioxide. 



Water - - eS'85 



Sulphur - - 3-76 



Arsenic - "25 



Iron - 58-25 83 per cent. Fe 2 O 3 . 



Copper - 4-14 



Zinc - -37 



Cobalt - - traces. 



Silver - - traces. 



Lead - - 114 



Lime - '25 



Oxygen and loss - 26 '93 



Insoluble residue 1*06 



100-00 



No. 3. Mixture of burnt ore and salt (the latter being about 

 12 per cent, of the whole), ground and passed through sieve of 

 about 16 holes per square inch. 



This mixture is furnaced during a period of 5| hours, at the 

 expiration of which time the copper has usually been almost 

 entirely converted into a soluble chloride of that metal. 



No. 4. Mixture of salt and burnt ore after calcination during 

 5 f hours. 



No. 5. Purple ore, or residue left from No. 4 after the ex- 

 traction of the copper by lixiviation with hot water and dilute 

 hydrochloric acid. 



This residue is chiefly employed for the " fettling " of puddling 

 furnaces, 



