Ill 

 ORE TESTING BY THE CYANIDE PROCESS 



A very important part of the duties of the chemist in a Cyanide 

 Works is to make extraction and consumption tests on the ores 

 received. It is not unusual, in large custom works, to make such 

 tests on each lot of ore received. But of greater importance, per- 

 haps, is the testing and examination of ores for the purpose of 

 determining their adaptability to cyanide treatment. 



PRELIMINARY TESTS. 



A physical examination of the ore will give a good idea of 

 the screen aperture through which it must be passed in order to 

 obtain a good extraction. For example; if the ore is a porous or 

 cellular oxidized product, perhaps, crushing through 0.44" screen 

 aperture will suffice; if of dense and solid structure it should be 

 crushed to pass screen apertures varying from 0.024 to 0.018-inch. 

 Flinty material, pyritic and telluric, silver ores, etc., may have to 

 be reduced to impalpable powder to obtain the desired extraction. 



Roasting, apart from oxidizing or driving off the volatile 

 metals, also resembles fine crushing in that it makes the ore 

 porous, allowing the solutions to penetrate the individual ore par- 

 ticles, much as if they had been reduced to a very fine state of 

 division. 



CONSUMPTION TEST. 



These are best made direct with cyanide solutions, and, as lime 

 is invariably used to correct acidity, add it at once and note results. 

 Weigh up 4A.T. of the crushed ore and place in 250 cc. glass stop- 

 pered bottle; add fresh slacked, pure lime at the rate of 5, 10, 15 

 and 20 lbs. to the ton of ore and 30 cc. of cyanide solution; place 

 on the agitator for 30 minutes, filter, and determine cyanide con- 

 sumption. 



The lowest consumption may be found with 10 lbs. of lime 



