Question

If a metal has low oxygen affinity, then the purification of metal may be carried out by:

• A. liquation
• B. distillation
• C. zone refining
• D. cupellation

Answer 1

Answer: (D)

cupellation

Liquation is applicable for metals such as $Sn,Pb$ and $Bi$, which have low melting points as compared to their impurities.

Fractional distillation process utilizes the boiling point difference between the metal and that of impurity.

Zone refining is based upon fractional crystallization as the impurity prefers to stay in the melt and on solidification, only pure metals solidify on the surface of the melt.

Cupellation is a refining process in metallurgy, where ores or alloyed metals are treated under very high temperatures and have controlled operations to separate noble metals, like gold and silver, from base metals like lead, copper, zinc, arsenic, antimony or bismuth, present in the ore. $\text{If a metal has low oxygen affinity}$, then the purification of metal may be carried out by cupellation.