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.
Metal iodide is decomposed on a tungsten filament, electrically heated to about 1800 K to give the pure metal.
Crayolite (Na3AlF6 or CaF2) is added to alumina to lower the melting point, and to increase the conductivity of the electrolyte.