what is van arkel method? explain briefly.
Van Arkel method (Vapour Phase Refining )
This method is based on the thermal decomposition of metal components. The process of decompositon of a compound into different substances due to the supply of heat is called thermal decomposition.
Titanium metal is purified by this method. When the impure titanium metal is heated with iodine at a temperature of 2500 C, volatile titanium tetra-iodide is formed (TiI4). The impurities are left behind, as they do not react with iodine.
The titanium tetra-iodide vapour is passed over a hot tungsten filament at 14000 C. The vapour is decomposed and pure titanium is deposited on the filament and is removed. The iodine is reused.