Decoction, or boiling, is employed to extract the mucilaginous or
gummy parts of substances, their bitter, astringent, or other
qualities, and is nothing more than boiling the ingredients in a
saucepan with the lid slightly raised. Be sure never to use an iron
saucepan for astringent decoctions, such as oak-bark, galls, &c., as
they will turn the saucepan black, and spoil the decoction. The
enamelled saucepans are very useful for decoctions, but an excellent
plan is to put the ingredients into a jar and boil the jar, thus
preparing it by a water bath, as it is technically termed; or by using
a common pipkin, which answers still better. No decoction should be
allowed to boil for more than ten minutes.