Which method of purification is represented by the following equator ? $T_{i(s)} +2I_{2(g)} \quad \underrightarrow{523 \;K} \quad TiI_{4(g)} \quad \underrightarrow{1700\;K} \quad T_{i(s)} +2I_2(g)$

Question

$\begin{array}{1 1} cupellation \\ vanArkel \\ poling \\ zone refining \end{array}$