(i) In the metllurgy of aluminimum, purified `Al_(2)O_(3)` is mixed with cryolite lowers melting point of the mix and brings conductivity.
(ii) CO-forms a volatile complex (Nickel tetralabonyl)
`Ni +4 Co overset(300-350K)rarrNi(CO)_(4)`
the carbonyl is subjected to higher temperature so that it is decomposed giving a pure metal.
`Ni[CO] overset(450-41 K)rarrNi+4CO`.