During roasting the temperature should be kept below its m.p. Why ?

Explanation

**Step-by-Step Solution:**

1. **Understanding Roasting**: Roasting is a metallurgical process where sulfide ores are heated in the presence of excess oxygen. This process converts the sulfide ores into oxides, which are typically more amenable to further processing.

2. **Temperature Control**: During roasting, it is crucial to maintain the temperature below the melting point of the ore. This is because if the temperature exceeds the melting point, the ore will melt.

3. **Consequences of High Temperature**: If the temperature is raised above the melting point, the molten ore can mix with volatile impurities present in the material. This mixing can lead to the formation of unwanted compounds or phases that can complicate the extraction process.

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