A metal extracted by any method is usually contaminated with some impurity. For obtaining metals of high purity, several techniques are used depending upon the differences in properties of the metal and the impurity. Some of them are listed below:

(a) Distillation

(b) Liquation

(c) Electrolysis

(d) Zone refining

(e) Vapour phase refining

(f) Chromatographic methods

Which of the following is not refined by zone refining method?

Gold

The correct answer is option 4. Gold.

The zone refining method is used primarily to purify semiconductors and other materials with high melting points and specific electronic properties. This method is particularly effective for elements that need to be extremely pure for electronic applications. The common elements refined by zone refining include germanium, silicon, and gallium.

Gold, however, is not refined by the zone refining method. Gold is typically refined by methods such as electrolysis, the Miller process, or the Wohlwill process, which are more suitable for purifying metals rather than semiconductors.

Therefore, the correct answer is Gold.