Compounds with a phenol group will form a blue, violet, purple, green, or red-brown color upon addition of aqueous ferric chloride. This reaction can be used as a test for phenol groups. Mix several ...

and aluminum powder), and others had extremely low rates of reaction (zinc [allergic rate, 0.1%], ferric chloride [0.1%], and tin [0.3%]). A particular strength of our study was that late readings ...

Metals with extremely low rates of allergic patch-test reactions included zinc, ferric chloride, and tin. Reaction rates varied depending on metal salt, concentration, and timing of readings.