In the van Arkel process .........is used to purify .............or........... .

Answer

**Step-by-Step Text Solution:**

1. **Identify the Process**: The question refers to the van Arkel process, which is a method used for the purification of certain metals.

2. **Determine the Metals Involved**: The van Arkel process is specifically used to purify zirconium and titanium.

3. **Chemical Reaction**: In this process, zirconium (or titanium) is reacted with iodine at a low temperature (around 473 K). This reaction produces a compound of zirconium (or titanium) with iodine.

4. **Heating the Compound**: The compound formed is then heated at a higher temperature (approximately 1635 K). This step leads to the decomposition of the compound, resulting in the formation of pure zirconium (or titanium) and iodine gas.

5. **Conclusion**: Thus, the van Arkel process is utilized to purify zirconium and titanium.

**Final Answer**: In the van Arkel process, iodine is used to purify zirconium or titanium.

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