Question

Tin is not refined by:

• A. Liquidation
• B. Zone refining
• C. Poling
• D. None of the above

Answer 1

Answer: (B)

Zone refining

Poling is a [metallurgical] method employed in the purification of copper which contains copper oxide as an impurity and also in the purification of tin ("Sn") which contains tin oxide (stannic oxide or "$Sn{O}_2$") as an impurity. It was the use of these greenwood poles gave rise to the term "poling."

Liquidation is suitable for metals with low melting points for example, tin. In this process, we heat the impure metal and then we let it flow on a sloped surface. The impurities will remain behind and the pure metal will collect at the bottom of the slope.

Zone refining is a special method we use to purify metals. It was the invention of William Pfann. It purifies metals to a very high degree. A rod of impure metal is placed in a container which we fill with inert gas. Then we place a circular heater around the rod at the top.

The melting point of tin is low. So zone refining is not suitable for Tin.

Hence, option B is correct.