Which method of purification is represented by the following equation:
$$\text{Ti(s)}+2{\text{I}}_2\text{(g)}\stackrel{523\text{K}}{\to }{\text{TiI}}_4\text{(g)}\stackrel{1700\text{K}}{\to }\text{Ti(s)}+2{\text{I}}_2\text{(g)}$$

The process shown involves the formation of a volatile iodide of the metal, which then decomposes at a higher temperature to give the pure metal. This is the Van Arkel method, used specifically for refining Titanium and Zirconium.