The correct answer is option 1. Titanium.
The van Arkel method is a purification technique used for certain metals, particularly those that readily form volatile compounds. This method is commonly employed for the purification of titanium.
Van Arkel Method for Titanium Purification:
1. Formation of Titanium Tetraiodide (\(TiI_4\)):
The first step involves reacting impure titanium metal with iodine to form titanium tetraiodide (\(TiI_4\)). The chemical reaction is as follows:
\[ Ti + 2I_2 \rightarrow TiI_4 \]
The titanium tetraiodide formed in this step is a volatile compound.
2. Formation of a Complex:
The \(TiI_4\) formed is often mixed with a small amount of an iodine crystal to form a complex. This complex is then heated to a specific temperature, causing the \(TiI_4\) to vaporize.
3. Decomposition of Titanium Tetraiodide:
In the final step, the vaporized \(TiI_4\) is decomposed back into pure titanium and iodine. This decomposition is achieved by passing the vaporized \(TiI_4\) over a heated filament or wire.
\[ TiI_4 \rightarrow Ti + 2I_2 \]
The iodine produced in this step can be condensed and reused in the process.
Significance:
The van Arkel method is particularly useful for the purification of titanium because titanium readily forms volatile compounds like \(TiI_4\).
The impurities that might be present in the original titanium metal are left behind in the residues, and the purified titanium is obtained through the decomposition of the volatile \(TiI_4\).
Applications:
Purified titanium obtained through the van Arkel method is essential for applications in various industries, including aerospace, medical implants, and chemical processing.
The high purity of titanium is crucial for maintaining its mechanical properties and corrosion resistance in different applications.
Other Metals:
While the van Arkel method is commonly associated with titanium, similar methods can be applied to other metals that form volatile compounds. The specific conditions and compounds involved may vary depending on the metal being purified.
In summary, the van Arkel method is a technique used for the purification of certain metals, and in this context, it is particularly employed for purifying titanium by forming and decomposing the volatile compound \(TiI_4\). | 
