Chemical tests in mushroom identification
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Iron salts are used commonly in Russula and Bolete identification. It is best to dissolve the salts in water (typically a 10% solution) and then apply to the flesh, but it is sometimes possible to apply the dry salts directly to see a color change. For example, the white flesh of Boletus chrysenteron stains lemon-yellow or olive. Three results are expected with the iron salts tests: no change indicates a negative reaction; a color change to olive, green or blackish green; or a color change to reddish-pink.
Meixner test for amatoxins
- Spores that stain bluish-gray to bluish-black are amyloid
- Spores that stain brown to reddish-brown are dextrinoid
This test is normally performed on white spored mushrooms. If the spores are not light colored, a change will not be readily apparent. 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.
A 3–10% solution of potassium hydroxide (KOH) gives a color change in some species:
- In Agaricus, some species turn yellow with KOH, some have no reaction, and one species turns green.
- Distinctive change for some species of Cortinarius and Boletes
Developed by Julius Schäffer to help with the identification of Agaricus species. A positive reaction of Schaeffer's 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.
Sometimes referred to as "Schaeffer's reaction", "Schaeffer's cross reaction" or "Schaeffer's test".
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