Page:Popular Science Monthly Volume 92.djvu/99

 Popular Science Mouihiy

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��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��Various Methods of Concentration Hand-shaking has long since been superseded by mechanical methods, some of which treat the ores wet, and some dry.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)

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