(i) The impure Zr or Ti is heated in an evacuated vessel with I2 so that all oxygen and nitrogen present in the form of impurities are removed.
Zr + 2I2→ ZrI4
The metal iodide is decomposed on a tungsten filament heated to 1800 K and the pure metal gets deposited on filament.
ZrI4 → Zr + 2I2
(ii) The purified alumina is mixed with cryolite to reduce the melting point and to increase the fusibility.
(iii) Impure silver is leached out with NaCN in presence of air to form a complex. From the complex pure metal is recovered by displacement using Zn.
4Ag + 8CN- +2H2O + O2→ 4[Ag(CN)2]- + 4OH-
2[Ag(CN)2]- + Zn → 2Ag + [Zn(CN)4]2-
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