Describe the role of the following:
(i) NaCN in the extraction of silver
(ii) CO in the purification of nickel
(i) Dilute NaCN forms a soluble complex with Ag or Ag2S while the impurities remain unaffected which are filtered ***.
(ii) Carbon monoxide forms a volatile complex, nickel tetracarbonyl with nickel which on decomposition gives pure nickel.
