Describe the roles of the following:

1. NaCN in the extraction of silver from a silver ore.

2. Iodine in the refining of titanium.

3. Cryolite in the metallurgy of aluminium.

Extraction of Silver

• In the extraction of gold and silver, the metal is leached with NaCN or KCN, which is an oxidation reaction.

• During the process, Ag is oxidised to Ag⁺ 

Here M =Ag or Au.

van Arkel Method for refining zirconium or titanium

• All the oxygen and nitrogen present as impurity are removed.

• Crude metal is heated with iodine in an evacuated vessel.

Ti+2I₂→TiI₄

• Metal iodide is decomposed on a tungsten filament, electrically heated to about 1800 K to give the pure metal.

TiI₄→Ti+2I₂

Crayolite (Na₃AlF₆ or CaF₂) is added to alumina to lower the melting point, and to increase the conductivity of the electrolyte.