State the importance of coordination compounds in metallurgical processes.

(N/A) Metallurgical processes: Some important extraction processes of metals,such as those of $Ag$ and $Au$,utilize complex formation.
$1$. Extraction: Gold $(Au)$ combines with cyanide in the presence of oxygen and water to form the coordination entity $[Au(CN)_2]^-$ in aqueous solution. Gold can be separated in metallic form from this solution by the addition of zinc.
$2$. Purification: Purification of metals can be achieved through the formation and subsequent decomposition of their coordination compounds. For example,impure nickel is converted to $[Ni(CO)_4]$,which is decomposed to yield pure nickel.