What will happen during lassaigne's test for nitrogen if the compound also contains sulphur ?

Answer

### Step-by-Step Solution:

1. **Understanding Lassaigne's Test**: Lassaigne's test is a qualitative analysis method used to detect the presence of nitrogen in organic compounds. It involves fusing the organic compound with sodium metal and then treating the resulting sodium extract with ferrous sulfate and hydrochloric acid.

2. **Formation of Prussian Blue**: If the compound contains only nitrogen, the test will yield a blue precipitate known as Prussian blue. This is represented by the formula Fe₄[Fe(CN)₆]₃·xH₂O. The formation of this compound indicates the presence of nitrogen in the sample.

3. **Introducing Sulfur**: If the compound also contains sulfur, the reaction changes. Instead of forming Prussian blue, the presence of sulfur leads to the formation of sodium thiocyanate (NaSCN).

4. **Color Change**: Sodium thiocyanate gives a red coloration when it reacts in the test. This red color can obscure the blue color that would indicate the presence of nitrogen.

5. **Conclusion**: Therefore, when both nitrogen and sulfur are present in the compound during Lassaigne's test, the formation of sodium thiocyanate results in a red coloration, making it difficult to confirm the presence of nitrogen due to the interference of sulfur.