Popular Science Mouihiy 



m 



found in conjunction with the sulphides of 



lead, copper and zinc, is referred to as 



gangue. Concentration is any process 



of separating the 



valuable metal 



from the worthless 



gangue. 



The simplest meth- 

 od of concentration 

 is hand-shaking. We 

 all remember our old 

 American history 

 which contained a 

 picture of a flannel- 

 shirted Forty-Niner 

 "panning out" gold 

 from one of Califor- 

 nia's rivers. He used 

 an ordinary dish-pan, 

 and by a careful 

 shaking, slopped the 

 water and gangue 

 over the sides, the 

 metal being allowed 

 to settle. 



Froth 

 concentrates 



Impeller 



Plaq 



The Interior of a Single Cell 



The pulp, consisting of sulphides, gangue, water 

 and oil, is violently agitated by the impeller. 

 From this chamber, it passes into the flotation 

 box or spitzkasten. The froth, bearing the 

 metal, is floated over the lip and the worthless 

 gangue is then allowed to sink to the bottom 



Various Methods of Concentration 

 Hand-shaking has long since been 

 superseded by mechanical methods, some 

 of which treat the ores wet, and some 

 dry. Both take ad- 

 vantage of the dif- 

 ference in specific 

 gravity of the. 

 gangue and of the 

 metal. In the dry 

 method, a current of 

 air is used to blow 

 away the lighter 

 gangue, leaving the 

 heavier minerals on a 

 flat corrugated sur- 

 face. In the wet 

 methods, the ore 

 passing through a 

 stream of water sepa- 

 rates into two parts, 

 the metals sinking 

 and the gangue being 

 washed away. 



But now comes a 



Spitz-kasten or 

 flotation box 



The Metal-Laden Froth After Running the Gantlet of Agitation Cells 



The feed passes through two agitation boxes before box. From this the pulp passes to the second spitz- 

 entering the spitzkasten where the first concentrate kasten. and so on down through the machine to 

 is removed by means of a paddle. The remaining the fourteenth spitzkasten. Discharge from No. 

 pulp passes through a pipe to the third agitation 14 leaves the machine as tailing Crefiise ore) 



