Q.The following set of reactions are used in refining Zirconium
Zr (impure) + 2I₂ --523 K--> ZrI₄
ZrI₄ --1800 K--> Zr (pure) + 2I₂
This method is known as

Step 1. Section 1.6.5 describes the Van-Arkel method for refining zirconium/titanium: the impure metal is heated with iodine at a lower temperature (around 550 K here, given as 523 K in this question) to form a volatile tetraiodide, then that vapour is passed over a hot tungsten filament (around 1800 K) where it decomposes, depositing the pure metal and regenerating iodine.

Step 2. The two-reaction pattern in the question -- Zr + 2I2 ->(523 K) ZrI4, then ZrI4 ->(1800 K) Zr(pure) + 2I2 -- exactly matches this Van-Arkel sequence: a volatile-compound-forming step at a lower temperature, followed by thermal decomposition at a much higher temperature to release the pure metal. …

Recognise the iodine-based volatile-compound-then-thermal-decomposition pattern shown in the reactions as the Van-Arkel method (Section 1.6.5), distinguishing it f …

• Confusing the Van-Arkel method (iodine, used for Zr/Ti) with Mond's process (carbon monoxide, used for Ni) -- both are vapour-phase refining methods with the same two-stage logic (form a volatil …