Question
Which solution is used for the leaching of silver metal in the presence of air in the metallurgy of silver?
Solution
Dilute solution of NaCN and KCN is used for leaching of silver metal in the presence of air in the metallurgy of silver, for example in the following reaction
AgS + 4NaCN ⇌ 2Na[Ag(CN)2] + Na2SAgS + 4NaCN ⇌ 2Na[Ag(CN)2] + Na2S
The solution of sodium Argento cyanide combines with zinc dust and forms sodium tetra cyanozicate and precipitated silver. This precipitated silver is called spongy silver.
Zn+2Na[Ag(CN)2] → Na2[Zn(CN)4] + 2AgZn + 2Na[Ag(CN)2] → Na2[Zn(CN)4] + 2Ag
The spongy silver is fused with potassium nitrate to obtain pure silver. Then the silver obtained is purified by an electrolytic process.
