refining of ores

Describe the principle behind each of the following processes : (i) Vapour phase refining of a metal. (ii) Electrolytic refining of a metal. (iii) Recovery of silver after silver ore was leached with NaCN.

Outline the principles of refining of metals by the following methods : (a) Electrolytic refining (b) Zone refining ( c) Vapour phase refining.

(a) Write the principle of method used for the refining of germanium (b) Out of PbS and PbCO_(3) (ores of lead), which one is concentrated by froth floatation process preferably ? (c) What is the significance of leaching in the extraction of aluminium ?