Chemical tests in mushroom identification are methods that aid in determining the variety of some fungi.
It is easiest to see the color change under a microscope, but it is possible to see it with the naked eye with a good spore print.
A 2–3% aqueous solution of phenol gives a color change in some species when applied to the cap or stem.
The test is considered positive when a bright orange color forms where the lines cross.
Kerrigan's 2016 Agaricus of North America P45: (Referring to Schaffer's reaction) "In fact I recommend switching to the following modified test.
Frank (1988) developed an alternative formulation in which aniline oil is combined with glacial acetic acid (GAA, essentially distilled vinegar) in a 50:50 solution.