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| Refining of the Metal |
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| Purification of the metal is the last step in metallurgy. |
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| Refining is based on the difference between the properties of metals and their impurities. |
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| This method is used for refining metals having a low melting point. |
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| e.g., tin, lead, bismuth |
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| Liquation |
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| Process |
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 The metal to be refined is placed over the sloping hearth of a furnace |
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The temperature of the furnace is maintained slightly above the melting point of the metal |
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Pure metal melt and flow down |
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Impurities, having higher melting point, are left behind |
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| This method is used for volatile metals having boiling points lower than their impurities. e.g., zinc, mercury. |
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| Process |
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The metal to be refined is heated above its boiling point |
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Impurities do not vapourise |
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Pure metal vapourises and is condensed |
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Impurities are left behind |
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| This method is used for refining copper, silver, tin, nickel. |
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| Refining of the metal |
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| Process |
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A block of impure metal is made the anode of an electrolytic cell containing an aqueous solution of the metal salt |
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A thin sheet of pure metal is made the cathode of the electrolytic cell |
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When electric current of a suitable voltage is passed, metal ions from the electrolyte get deposited on the cathode as pure metal M+n + ne- g M |
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Metal ions from the anode enter the electrolyte M g M+n + ne- |
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Impurities present in the anode settle down as anode mud under the anode |
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Anode finally disintegrates while the cathode gains in weight due to the collection of pure metal |
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