Question

Explain liquefaction and zone refining method for refining of metals.Answer the given question in detail.

Answer 1

Some metals after reduction still contain some impurities which is further removed by refining. Two of which methods are:
$\bf{Liquefaction}$: This method is used for the metals having low melting point such as lead, tin, etc.
In this method furnace having a slope is used and the temperature of the furnace is kept higher than the melting point of metal.
When the impure metal is passed on the slope, the metal in it get melted and collected in the vessel but the melting point of impurities is high so they remain on the slope in solid form.

$\textbf{Zone refining}$: This method is based on the principle of fractional distillation to get a very high level of purity. Refining of semi metals is done by this method. In this method we remove trace impurities which are generally more soluble in molten metal, their solubility decreases as the metal cools and impurities are separated in the form of crystals.