Improvements relating to the extraction of pyrethrum

摘要

Pyrethrins are extracted from dried or undried pyrethrum flowers with a solvent consisting of methanol, ethanol or isopropyl alcohol and 5 to 40% by weight of water followed by liquid/liquid extraction of the solution with a hydrocarbon solvent such as kerosene or isohexane which can be distilled off. The water may be present originally if the flowers are fresh and undried.