Explain the purification of metals in the vapour phase with an example.

(N/A) Principle: In this method,the metal is converted into its volatile compound and collected,which is then decomposed to give the pure metal. The two requirements for this method are:
$(i)$ The metal should form a volatile compound with an available reagent.
$(ii)$ The volatile compound should be easily decomposable to recover the metal.
Example: Mond process for refining Nickel.
$Ni + 4CO \xrightarrow{330-350 \ K} Ni(CO)_4$
$Ni(CO)_4 \xrightarrow{450-470 \ K} Ni + 4CO$