The refining method used when the metal and the impurities have low and high melting temperatures, respectively, is

Options

A. vapour phase refining
B. liquation
C. zone refining
D. distillation

Answer

To solve the question regarding the refining method used when the metal has a low melting point and the impurities have a high melting point, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Characteristics of the Metal and Impurities**:
- The question states that the metal has a low melting point, while the impurities have a high melting point. This is crucial for determining the appropriate refining method.

2. **Consider Possible Refining Methods**:
- There are various refining methods available, including:
- Zone refining
- Vapour phase refining
- Distillation
- Liquefaction

3. **Analyze Each Method**:
- **Zone Refining**: This method is based on the principle that impurities are more soluble in the molten state than in the solid state. It does not specifically address the melting points of the metal and impurities.
- **Vapour Phase Refining**: This method is used for metals that can form volatile compounds. It does not focus on the melting points of the metal and impurities.
- **Distillation**: This method is effective for separating components based on boiling points, not melting points.
- **Liquefaction**: This method is particularly relevant here because it involves the separation of a metal with a low melting point from impurities with a higher melting point. The metal is melted and allowed to flow away from the solid impurities.

4. **Conclusion**:
- Given that the metal has a low melting point and the impurities have a high melting point, the appropriate refining method is **Liquefaction**. This method allows the low melting point metal to be separated from the higher melting point impurities effectively.

5. **Final Answer**:
- The refining method used when the metal and the impurities have low and high melting temperatures, respectively, is **Liquefaction**.