Question

Which method of purification is used for refining titanium?

• A. Zone refining
• B. Van Arkel method
• C. Mond process
• D. Liquation

Hint:

Remember the important refining methods:

• Van Arkel Process $\rightarrow$ Titanium, Zirconium

• Mond Process $\rightarrow$ Nickel

• Zone Refining $\rightarrow$ Silicon, Germanium

• Liquation $\rightarrow$ Tin, Lead
A common exam question is to match metals with their purification methods, so memorizing these standard pairs is very useful.

Answer 1

The Correct Option is B

Concept: Metals obtained from their ores usually contain impurities. To obtain metals of extremely high purity for scientific, industrial, and technological applications, special refining methods are employed. Different metals are purified by different methods depending on their physical and chemical properties. Some important refining methods are:

• Liquation – Used for low melting metals such as tin and lead.

• Zone Refining – Used for ultra-pure semiconductors like silicon and germanium.

• Mond Process – Used for purification of nickel.

• Van Arkel Method – Used for purification of titanium and zirconium.
The purification of titanium is achieved by the Van Arkel process, also known as the iodide process.

Step 1: Understanding the Van Arkel Method
The Van Arkel method is based on the formation and subsequent decomposition of a volatile metal iodide. In this process:

• Impure titanium is heated with iodine.

• Titanium reacts with iodine to form volatile titanium tetraiodide.
The reaction is: \[ Ti + 2I_2 \rightarrow TiI_4 \] Titanium tetraiodide is volatile and can therefore be separated from the impurities.

Step 2: Decomposition of Titanium Tetraiodide
The volatile titanium tetraiodide vapors are passed over an electrically heated tungsten filament. At high temperature, titanium tetraiodide decomposes: \[ TiI_4 \rightarrow Ti + 2I_2 \] Pure titanium gets deposited on the tungsten filament while iodine is regenerated and reused. Thus extremely pure titanium is obtained.

Step 3: Examination of Each Option

Option (A): Zone Refining Zone refining is employed for obtaining ultra-pure semiconductors and certain metals. Examples include:

• Silicon

• Germanium

• Gallium
It is not the standard method used for titanium purification. Therefore, \[ \boxed{\text{Option (A) is incorrect}} \]

Option (B): Van Arkel Method This method specifically purifies titanium and zirconium through volatile iodide formation. Therefore, \[ \boxed{\text{Option (B) is correct}} \]

Option (C): Mond Process Mond process is based on the formation of volatile nickel carbonyl. \[ Ni + 4CO \rightarrow Ni(CO)_4 \] It is used for refining nickel and not titanium. Hence, \[ \boxed{\text{Option (C) is incorrect}} \]

Option (D): Liquation Liquation is suitable for metals having low melting points such as lead and tin. Titanium has a very high melting point and therefore cannot be refined by this method. Hence, \[ \boxed{\text{Option (D) is incorrect}} \]

Step 4: Final Conclusion
Titanium is purified by converting it into volatile titanium tetraiodide and then decomposing it on a hot tungsten filament. This refining technique is known as the

Van Arkel Method. Therefore, \[ \boxed{\text{Van Arkel Method}} \] and hence the correct answer is \[ \boxed{\text{Option (B)}} \]