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Reduction

This term is applied to a process by which the oxygen is withdrawn from a metallic oxide, leaving the base in its original state. This is effected by heating the oxide with carbon or hydrogen; or by exposing it to the action of some other body which has a powerful affinity for oxygen. A portion of the metallic oxide to be reduced, is mixed with finely powdered charcoal and exposed in a crucible to the heat of a furnace. be crushed or pulverized, to expose the largest The metallic residue, which remains after reduction by this means, is usually mixed with Substances which in the lump would remain coal dust. This is prevented by lining the crucible with charcoal dust made into a dough with clay and water, leaving a space in the middle to receive the metallic oxide, not mixed with charcoal, as in the former instance; the crucible must be covered, and then heated.

The reduction in this way is slower, but the Professor Youmans, in the "Hand Book of Household Science," says: "Solids should surface to the action of the solvent liquid. for days undissolved, when reduced to powder are liquefied in a short time. When a solid, as common salt or alum, is placed in a vessel of water to dissolve, it rests at the bottom.

The water surrounding it becomes saturated, and being heavier, remains also at the bottom, so that the solution proceeds very slowly. metal will be pure and free from coal dust. By stirring, the action is hastened, but this When hydrogen is employed for reduction, the metallic oxide is heated to redness in a glass or porcelain tube, and subjected to a current of hydrogen gas, which absorbs the oxygen, and leaves the metal pure. Other agents are sometimes used for reducing, as tallow, oil, resin, sugar, and starch; but carbon and hydrogen are the agents generally employed.