Given below are two statements:
Statement I: Sulphanilic acid gives esterification test for carboxyl group.
Statement II: Sulphanilic acid gives red colour in Lassigne's test for extra element detection.
In the light of the above statements, choose the most appropriate answer from the options given below:

We need to evaluate two statements about sulphanilic acid ($$H_2N-C_6H_4-SO_3H$$, also known as 4-aminobenzenesulphonic acid).

The first statement claims that sulphanilic acid gives the esterification test for a carboxyl group. This is incorrect. Sulphanilic acid contains a sulphonic acid group ($$-SO_3H$$), not a carboxyl group ($$-COOH$$). The esterification test involves reacting a carboxyl group with an alcohol in the presence of an acid catalyst to form a fruity-smelling ester, a reaction that sulphonic acid groups do not undergo. Therefore, sulphanilic acid will not give a positive esterification test for a carboxyl group.

The second statement asserts that sulphanilic acid gives a red colour in Lassaigne’s test for extra element detection. This is correct. Sulphanilic acid contains both nitrogen (in the $$-NH_2$$ group) and sulphur (in the $$-SO_3H$$ group). When subjected to sodium fusion (Lassaigne’s) test, these elements form sodium thiocyanate according to:

$$ Na + C + N + S \to NaSCN $$

Upon adding ferric chloride (FeCl$$_3$$) solution to the extract, the reaction is:

$$ 3NaSCN + FeCl_3 \to Fe(SCN)_3 + 3NaCl $$

Ferric thiocyanate, Fe(SCN)$$_3$$, imparts a characteristic blood-red colour, confirming the presence of both nitrogen and sulphur.

Thus, the correct answer is Option 4: Statement I is incorrect but Statement II is correct.