Explain refining of titanium by Van-Arkel method.

Explanation

(i) Van-Arkel method is based on the thermal decomposition of metal compounds which lead of the formation of pure metals.
(ii) Titanium and ziroconium can be purified using this method.
(iii) For example, the impure titanium metal is heated in an evacuated vessel with iodine at a temperature of 550 K to form the volatile titanium tetra-iodide. `(Til_(4))`.
(iv) The impurities are left behind, as they do not react with iodine.
`Ti_((s)) + 2I_(2(s)) rarr TiI_(4)` (vapour)
(v) The volatile titanium tetraiodide vapour is passed over a tungsten filament at a temperature around 1800 K.
(vi) The titanium tetraiodide is decomposed and pure titanium is deposited on the filament.
(vii) The iodine is reused.
`TiI_(4) ("vapour") rarr Ti_((s)) + 2I_(2(s))`