Refining of metals

The refining of a metal is the procedure which aims at purifying a rough metal. At the end of an operation of refining the purity of metal exceeds 99,9% in general and sometimes 99,999%.

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Description

A metal often produced by reduction of its oxide is generally not produced with a sufficient degree of purity to be used in a stage. There remain generally impurities which one wants to eliminate either because they are harmful for the properties of metal (trace of carbon and phosphorus in steel which degrade its mechanical properties) or because they have value (gold and money in copper for example). Refining is done is in a furnace (for steel for example) where the molten metal is purified by oxidation of the impurities, either by distillation (zinc), or by electrolysis (copper, aluminum). Whenever extreme purities are necessary (electronics) one has recourse to the technique of the molten zone which makes it possible to reach 10^-11%d' impurity

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