Explain why :
A black precipitate is obtained in the Lassaigne's test for the detection of sulphur.

Explanation

### Step-by-Step Solution:

1. **Understanding Lassaigne's Test**:
- Lassaigne's test is a qualitative analysis method used to detect the presence of certain elements, including nitrogen, sulfur, and halogens, in organic compounds.

2. **Fusing Sodium with the Organic Compound**:
- In this test, sodium metal is fused with the organic compound. This process converts the sulfur present in the organic compound into sodium sulfide (Na2S).
- The reaction can be represented as:
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