Naturally occurring chemical compounds are found in a variety of sources and invariably are present as mixtures. It is the task of the natural products chemist to isolate and purify specic components, usually to homogeneity, in order to identify the chemical structure. A variety of separation techniques is available. Generally, the rst step is the use of a solvent (aqueous, organic, or liquid CO2, etc.) to dissolve organic material, and the solute is separated from the marc (plant residue) or the mycelia (fermentation). By concentrating the solvent an ideal outcome would be crystallization! This is rare and generally other separation steps are required.