Question

why salicylic acid gives violet colour with ferric chloride solution

Answer 1

Salicylic also known as benzoic acid -2 hydroxy gives violet colour with ferric chloride solution. I can analyze this reaction further for you to understand what happens.

Ferric chloride, or iron(III) chloride will not react with aspirin diurectrly . For the first time it will, however, react with salicylic acid, which is used to synthesize aspirin. Then adding an aqueous ferric chloride that is iron (III) chloride solution to a sample of aspirin is a good way to see if there is any unreacted salicylic acid. A purple color is an indication of salicylic acid.