Which method is used for refining `Zr` and `Ti`? Explain with equation.

Explanation

Van Arkel method is used for refining Zr and Ti. In this method crude metal is heated with iodine to form volatile unstable compound. The compound is then decomposed to get pure metal.
`underset("Impure")(Zr) + 2I_2 overset(870K)to ZrI_4`
`ZrI_4 overset("1800K")to underset("Pure")(Zr) + 2I_2`
`underset("Impure")(Ti) + 2I_2 overset(523K)to TiI_4 (g)`
`TiI_4 overset(1700 K)to underset("Pure")(Ti) + 2I_2`