Name the important ore of silver. Write all the steps and reactions involved in the cyanide process for the extraction of silver from its ore.

Explanation

Argentite (silver glance), `Ag_(2)S` or Horn silver `(AgCl)`
Concentration : The sulphide ore is crushed, powdered and then concentrated by the Froth flotation process.
Treatment with sodium cyanide : The concentrated ore is agitated with dilute solution of `NaCN` in the presence of air, When soluble sodium argentocyanide is obtained.
`Ag_(2)D+4NaCN hArr 2Na[Ag(CN)_(2)]+Na_(2)S`
`Na_(2)S+2O_(3)toNa_(2)SO_(4)`
`Ag_(2)S+4NaCN+2O_(2)to2Na[Ag(CN)_(2)]+Na_(2)SO_(4)`
Precipitation of silver :
`2Na[Ag(CN)_(2)]+ZntoNa_(2)[Zn(CN)_(4)]+2Agdarr`
Silver, thus obtained is in the form of dark amorphous mass.
Fusion : The precipitated silver is filtered, pressed, dried and fused with borax when a bright compact mass is obtained.
Electrolytic refining process : Silver thus obtained usually contain impurities of Zn, Cu and gold. So, thin sheet of pure silver is used as cathode and a block of impure silver is used as anode. `K[Ag(CN)_(2)]` or a solution of silver nitrate containing `1%" HNO"_(3)` is used as a electrolyte. On passing electricity pure silver gets deposited on the cathode.