Mond process for metal refining: In this process, nickel is heated in a stream of carbon monoxide forming a volatile complex, nickel tetracarbonyl:

$\mathrm{Ni} + 4\mathrm{CO} \stackrel{330 - 350\mathrm{K}}{\to } \mathrm{Ni}(\mathrm{CO}{)}_4$

The carbonyl is subjected to a higher temperature so that it is decomposed giving the pure metal:

$\mathrm{Ni}(\mathrm{CO}{)}_4 \stackrel{450 - 470\mathrm{K}}{\to } \mathrm{Ni} + 4\mathrm{CO}$