One other method of extracting chemicals from plants is by distillation. Distillation has not much to do with solubility but rather vaporization points. It allows a volatile substance to be separated fro a non volatile substance. Distillation is probably most widely used for producing alcoholic beverages after fermentation of plant sugars by yeasts. Ethanol boils at 78ºC while water boils at 100ºC. Because of its lower boiling point, ethanol will begin to boil and evaporate (turn to gas) when heated before the water does. Using a proper apparatus to collect and condense the steam, ethanol will be separated from the water. This process is of course not complete because much of the water will evaporate at the same time. Below is a picture of a basic distillation unit.
Part of this article was extracted from a presentation I gave at the International Herb Association, 2007.