Developed by Julius Schäffer to help with the identification of Agaricus species. A positive reaction of Schaeffers test, which uses the reaction of aniline and nitric acid on the surface of the mushroom, is indicated by an orange to red color; it is characteristic of species in the section Flavescentes'. The compounds responsible for the reaction were named schaefferal A and B to honor Schäffer.
Two intersecting lines are drawn on the surface of the cap, the first with aniline or aniline water, the second with an aqueous solution of 65% nitric acid. The test is considered positive when a bright orange color forms where the lines cross.
Agaricus placomyces and Agaricus xanthodermus produce false negative reactions.
Sometimes referred to as "Schaeffers reaction", "Schaeffers cross reaction" or "Schaeffer's test".