Which colour will appear in the Lassaigne's test if the compound contains both nitrogen and sulphur ?

Answer

To determine the color that appears in Lassaigne's test when a compound contains both nitrogen and sulfur, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Lassaigne's Test**:
Lassaigne's test is used to detect the presence of certain elements (like nitrogen and sulfur) in organic compounds. When an organic compound is fused with sodium, it forms sodium salts of the elements present in the compound.

2. **Formation of Sodium Thiocyanate**:
When the organic compound containing nitrogen and sulfur is fused with sodium, sodium thiocyanate (NaCNS) is formed. The reaction can be represented as:
\[ \text{Organic compound} + \text{Na} \rightarrow \text{NaCNS} + \text{other products} \]

3. **Reaction with Ferric Chloride**:
The sodium thiocyanate (NaCNS) formed in the previous step is then treated with ferric chloride (FeCl₃). This leads to the formation of ferric thiocyanate (Fe(CNS)₃). The reaction can be represented as:
\[ \text{NaCNS} + \text{FeCl}_3 \rightarrow \text{Fe(CNS)}_3 + \text{NaCl} \]

4. **Color of Ferric Thiocyanate**:
The ferric thiocyanate (Fe(CNS)₃) produced in this reaction imparts a characteristic color. The color of this complex is **blood red**.

5. **Conclusion**:
Therefore, if the compound contains both nitrogen and sulfur, the color that will appear in Lassaigne's test is **blood red**.

### Final Answer:
The color that will appear in Lassaigne's test if the compound contains both nitrogen and sulfur is **blood red**.