Refining of metals means purification of metals. Depending upon the nature of the metal and the nature of the impurities, present different methods are applied for the refining of metals. Some of the commonly used methods are discussed below:
1. Distillation
Volatile meals like zinc and mercury are purified by this method. The non-volatile impurities are left behind in the retort.
2. Liquation
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The method is used for easily fusible like bismuth, tin and lead. The crude metal is placed on the sloping hearth of a furnace and heated gently when the metal melts and flows down, leaving behind the infusible impurities which remain sticking to the floor of the hearth.
3. Poling
Some impurities have greater affinity for oxygen than for the metal. When the molten metal is stirred with green wood poles, the impurities come to the surface, get oxidised and form a scum which can be removed. Wood gases (hydrocarbons from wood) reduce any oxide of the metal back to the metal. Copper and tin are purified by this process.