Question

The sodium test, or Lassaigne’s test, is used in an elemental analysis of the qualitative determination of the presence of foreign elements, namely halogens, nitrogen, sulphur and phosphorus in an organic compound.
The test involves heating the sample strongly with a clean sodium metal, ‘fusing’ it with the sample. The ‘fused’ sample is then plunged into water, and the usual qualitative tests are performed on the resultant solution for the respective possible constituents.

When both $N$ and $S$ are present in an organic compound, the sodium extract with $FeC{l}_3$ gives a:

• A. Green colour
• B. Blue colour
• C. Yellow colour
• D. Red colour

Answer 1

The correct option is D Red colour

When both `S` & `N` are present in the organic sample then with lassaigne test compound formed is $NaSCN$ which upon reaction with $FeC{l}_3$ gives $\underset{bloodredcolour}{Fe(SCN{)}_3}$.