Which of the following can be used as laboratory test for phenol?

Blue litmus paper becomes crimson when phenol is present. This demonstrates that phenol is naturally acidic. Similarly, carboxylic acid performs this test. Phenol is a weaker acid than carboxylic acid, and it does not effervesce when combined with aqueous sodium carbonate. laboratory test for phenol gives purple colour with neutral ${\mathrm{FeCl}}_3$