A laboratory or kitchen device for extracting organic compounds from raw vegetable or mineral sources such as leaves, flowers, soils or sludges.

Despite the strange (Albanian?) name, soxhlets are fairly simple and very useful, both to lab technicians and kitchen chemists. I learned of them a long time ago as the first step in making honey oil, but now I use one to extract oils from lavender, sage, roses, and other nice-smelling stuff in our garden. Or at least, try to: this is a lossy process and in situ concentrations are low, so it takes acres of flowers to make an ounce of attar.

The way soxhlets work is this: the raw material to be extracted from is crushed or diced and placed on a metal screen over a small container of solvent that has a boiling point lower than that of water. For simplicity and non-toxicity I use Everclear. This apparatus is placed on a stand inside a larger container of water and the whole is covered with a tight-fitting lid. The shape of the lid is very important for this application: it must be concave, ie. pointing downward and coming to a point above the screen. This is because you will put ice onto the outside of the lid to make it act as a condenser. Put the whole rig over just enough heat to make the alcohol boil but not the water. The alcohol vapor will rise until it hits the cool container lid, where it will condense, run down the inside of the lid, and drip onto and through the raw material. As it does so it dissolves whatever oils, resins or other substances the material contains and carries them down into the inner solvent container, from where the alcohol is boiled again, rises, and the process repeats.

A soxhlet is meant to be run for an extended period of time, often several hours, washing the raw material thoroughly with solvent until it is completely blanched. Care should be taken to periodically rotate or redistribute the raw material on the screen under the condensing solvent drip for complete saturation and better extraction. At that point you remove the inner container and /very slowly/ boil it over much-reduced heat in the open air (or simply open and allow natural evaporation), to leave you with your attar of rose or whatever.

A soxhlet is the proper first step in the procedure for extracting organic oils; the procedure mentioned here is more appropriately the next step in a series of successive refinements with different solvents such as ether, carbon tetrachloride etc. Different solvents extract different subsets of the soluble constituents in a material; but the soxhlet provides the initial separation.

Safety Note: Putting volatile liquids anywhere near heat sources is dangerous. Use an electric burner rather than open flame, keep containers tightly closed, use common sense. If you use solvents more toxic than ethyl alcohol, be very careful to completely evaporate them from the final product. If you use carbon tet you'd better be in a lab using an exhaust hood, 'nuff said.

Log in or register to write something here or to contact authors.