Write two basic requirements for refining of a metal by Mond’s process and by van Arkel Method.

(b) van Arkel method includes conversion of $\mathrm{Zr}$ to volatile ${\mathrm{ZrI}}_{4}$ and then decomposition of ${\mathrm{ZrI}}_{4}$ to $\mathrm{Zr}$ and ${\mathrm{I}}_{2}$.