Write the role of
(a) Dilute in the extraction of Gold.
(b) in the extraction of Iron.
(a) NaCN acts as a leaching agent and it forms complex with gold.
[Ag(CN)2] - 4Au + 8CN– + 2H2O + O2 --------> 4 [Au(CN2)] – + 4OH–
(b) CO acts as a reducing agent.