Write the principle of the method used for refining of germanium.

Explanation

### Step-by-Step Solution:

1. **Identify the Method**: The method used for refining germanium is known as **Zone Refining**.

2. **Understanding Zone Refining**: Zone refining is a process that involves melting a small region (or zone) of a solid material and moving this molten zone along the length of the solid.

3. **Principle of Zone Refining**: The principle behind zone refining is based on the difference in solubility of impurities in the molten and solid phases of the material. When the molten zone moves through the solid, impurities tend to remain in the molten phase while the pure material crystallizes out.

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