what is the role of iodine in van arkel method?

Dear Student, 
Please find below the solution to the asked query: 

Van Arkel method is a method to obtain ultrapure metal from crude metal.  The method involves converting the metal into a volatile salt.  The pure metal is recovered by heating the salt. The method is used to purify Ti using iodine..

The role of iodine in the process is:

1. It is capable of forming a volatile salt, TiI₄, with Ti. This process removes the impurities present in crude Ti.
2. TiI₄ decomposes on heating at 1800 K to give pure Ti and iodine. Iodine is removed from the mixture as it directly converts into gas from solid on heating. The reactions are:

                                   Ti + 2I₂ $\to$      TiI₄
                                 TiI₄ $\stackrel{1800 K }{\to }$      Ti + 2I₂


Hope this information will clear your doubts about role of iodine in Van Arkel method,
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