. Appleton's dictionary of machines, mechanics, engine-work, and engineering. h. The heavier particles near the bottom are carried to the valves and passthrough these, the coarse through the opening B, and the smaller through C, forming heaps below,from which tbe remaining light impurities flow oft. This apparatus is simple, effective, and maybe applied in all instances where washing is to bo done. Various modes and machines are usedin Europe to remove the earthy matter from the ore by washing. Complicated sifting machinesare employed, the grilles or step-washings of Hungary, percussion-tables
. Appleton's dictionary of machines, mechanics, engine-work, and engineering. h. The heavier particles near the bottom are carried to the valves and passthrough these, the coarse through the opening B, and the smaller through C, forming heaps below,from which tbe remaining light impurities flow oft. This apparatus is simple, effective, and maybe applied in all instances where washing is to bo done. Various modes and machines are usedin Europe to remove the earthy matter from the ore by washing. Complicated sifting machinesare employed, the grilles or step-washings of Hungary, percussion-tables, shaking-tables, German-chests,sleeping-tables, swing-sieves, and a host of other machines, all of which are of no use to us; these ma-chines work too slow, absorb too much labor, and are not advantageous to our modes of working. Theabove wash apparatus, properly modified in particular eases, is all-sufficient for washing any bind ofore, and purifying it so far as necessary. Roasting of ores.—This process is sometimes performed on the ores when brought from the mine, as. 396 METALLURGY. 2810. is the case with iron ore, or it is performed after the ores are crushed, which is the way of working sil-ver ores in North Carolina. The principle involved in this operation is to drive off all that, volatile mat-ter from the ore which may be dissipated by heat; such as water, carbon, sulphur, phosphorus, chlorine,arsenic, zinc, <fec. The consequence of this operation, if well performed, is in all cases, with but fewexceptions, the oxidation of the remaining metals to their highest degree ; a condition in which the oresare most easily worked, and reduced by carbon to the metallic state. Roasting is performed in thiscountry almost exclusively in the open air; experiments made on roasting ovens met in but few instan-ces with success. There is no doubt but that roast ovens are more economical in the use of fuel thanheaps in the open air, but the ovens require more labor; and as fuel is
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Keywords: ., bookcentury1800, booksubjectmechanicalengineering, bookyear1861
