The Patio and Cazo Process. 



21 



tried with what seemed to bo, in many cases, great success for 

 a time ; but the cost of repairs has eventually caused the return 

 to the old way of treacling with mules, which will probably be 

 used until the process disappears. The pile is trodden and spaded 

 during the day. The next morning it is again trodden by the 

 mules for an hour or two, and spaded again ; after which, the 

 " magistral" is added. This substance was formerly a mixture of 

 the sulphates of copper and iron, obtained exclusively by roasting 

 iron pyrites in double-hearthed furnaces called comalillos. It 

 contains some gangue, but this does not affect the treatment. 

 The substance, however, is not of equal composition, as it is 

 obtained by roasting copper pyrites of very variable yield. 

 The following analyses of this magistral show how it may vary. 



Soluble in 



Water. 





Insoluble in Water. 







Poor.* 



Best.t 





Poor. 



Besr. 



Water, - 



7.60 



14.84 



Oxide of copper 



, - 5.70 



0.62 



Oxids of copper, 



2.50 



6 44 



Oxide of iron, - 



- 20.50 



23.20 



Oxide of iron, 



0.57 



0.20 



Oxide of lead, - 



- 0.00 



7.35 



Lime, 



3.17 



0.00 



Lime, 



- 7.84 



0.00 



Soda, - 



1.47 



4.19 



Silica, 



- 38.00 



28.82 



Sulphuric acid, 



9.15 



9.61 



Sulphur, 



- 2.22 



2.80 



Chlorine, 



0.12 



2.47 



Insoluble, 



74.26 



62.79 













Soluble, 



24.58 



37.75 





24.58 



37.75 













98.81 



100.54 











Poor. 



Best. 



Sulphats of Copper, 



- 



- 





9.03 



19.00 



Oxide of Copper, 



- 



- 



- 



5.00 



5.50 



Sulphate of Iron, 



- 



- 



. 



6.75 



14.80 



Sesquioxide of Iron, 





- 



- 



18 75 



25.80 



Insoluble, 



- 



- 



- 



60.47 



34.90 



100.00 



100.00 



In Peru, J an ore of copper which contains as high as 13.62 

 per cent, of sulphate of copper, already an excellent magistral, 

 is used for making it. This is roasted with salt, and when 

 finished and ready to be used, contains about half the soluble 



* Annales des Mines, 6th Series, Vol. 20, pp. 75, 76. 

 f Berg unci Hiitteumiinnische Zeitung, 1881, p. 302. 



\ Ibid. 



