In the Mond Process (also known as the Carbonyl Process), carbon monoxide combines with Nickel at 50-60 C to form nickel tetracarbonyl gas. This removes nickel from impurities, none of which form a carbonyl at such a low temperature. Heating nickel tetracarbonyl to 220-250 C decomposes it into pure nickel and carbon monoxide. Nickel can be deposited on an object that is heated to the nickel tetracarbonyl decomposition temperature in the presence of the gas; the process can also be engineered to produce fine nickel particles. Nickel produced in this manner is referred to as carbonyl nickel.
Various other metal carbonyls such as Iron pentacarbonyl and Chromium hexacarbonyl form at various temperatures and pressures, giving the possibility for separating pure metals from mixtures in a similar manner to nickel. Iron carbonyl extraction in particular is already utilized in terrestrial applications for the production of very pure iron particles, known as carbonyl iron.