The wood contains no tannin, and for this reason quassia, like chiretta and calumba, may be preserved with iron.
Substances containing tannic or gallic acid turn black when compounded with a ferric salt, so it cannot be used in combination with vegetable astringents except with the infusion of quassia or calumba.
The infusion is useful as a bitter tonic - a group of substances of which calumba is the type - and is also a very efficient anthelmintic for the threadworm (Oxyuris vermicularis).
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