What is the nature of elements which are purified by zone-refining method ?

Explanation

### Step-by-Step Solution

1. **Understanding Zone Refining Method**:
- The zone refining method is a technique used for purifying certain elements. It is based on the principle that impurities are more soluble in the molten state of a metal than in its solid state.

2. **Principle of Zone Refining**:
- In this method, when an impure metal is melted, the impurities tend to remain in the molten phase. As the molten metal is allowed to cool, pure metal crystallizes out, leaving the impurities behind in the liquid phase.

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