Which among the following elements is obtained in pure form by the zone refining process?

Explain chromatographic methods to refine the elements.

Which of the following does not represent a correct method for the extraction or refining of metals?

Which of the following statements are correct related to metallurgy?
$A$. In electrolytic refining of copper,pure $Cu$ is used as anode.
$B$. Zone refining is based on the principle that impurities are more soluble in the melt than in the solid state of the metal.
$C$. $TiI_4$ upon heating will give pure $Ti$.
$D$. Very pure $Zr$ may be obtained by galvanisation.
$E$. In copper smelting,hot air is used to convert to $CuSO_4$.
The correct answer is

Which method of refining nickel is represented by the following equation?
$Ni$ (impure) $+ 4CO$ $\xrightarrow{320 \ K} Ni(CO)_4$ $\xrightarrow{420 \ K} Ni$ (pure) $+ 4CO$

Explain electrolytic refining.