[lizaW]

The other day I was preforming an experiment and when acetaminophen and acetylsalicylic acid(resp. paracetamol and aspirin) were added to an NaOH solution with pH 14 the solution turned blue. The acetaminophen solution itself first turned blue and the acetylsalicylic acid solution was colorless. Any ideas why the solution turns blue?

[pgk]

Formation of acetaminophen sodium salt at such a high pH, causes a significant auxochromy to the visible light (violet-blue region). Furthermore, addition of sodium acetylsalicylate may increase the auxochromy, by formation of a π-charge complex compound.