Step 1: Understanding liquation.
Liquation is a process used to refine metals by melting and separating them from impurities. It is especially used to refine tin and lead.
Step 2: Analyzing the options.
(A) Liquation: Correct — Liquation is used to refine tin, specifically pig tin, by heating it to a temperature where impurities are removed.
(B) Mond process: This process is used to purify metals like nickel.
(C) van Arkel: This is a process used to refine metals such as titanium.
(D) Polling: Polling is used to purify tin but does not refine pig tin.
Step 3: Conclusion.
The correct answer is (A) Liquation, as it is the process used for refining pig tin.