- Soxhlet extractor
A Soxhlet extractor is a piece of
laboratory apparatus invented in1879 byFranz von Soxhlet [Soxhlet, F. Die gewichtsanalytische Bestimmung des Milchfettes, Polytechnisches J. (Dingler's) 1879, 232, 461] . It was originally designed for the extraction of alipid from a solid material. However, a Soxhlet extractor is not limited to the extraction of lipids. Typically, a Soxhlet extraction is only required where the desired compound has only a limitedsolubility in asolvent , and the impurity isinsoluble in that solvent. If the desired compound has a high solubility in a solvent then a simplefiltration can be used to separate the compound from the insoluble substance.Normally a solid material containing some of the desired compound is placed inside a
thimble made from thickfilter paper , which is loaded into the main chamber of the Soxhlet extractor. The Soxhlet extractor is placed onto a flask containing the extractionsolvent . The Soxhlet is then equipped with acondenser .The solvent is heated to
reflux . The solvent vapour travels up adistillation arm, and floods into the chamber housing the thimble of solid. The condenser ensures that any solvent vapour cools, and drips back down into the chamber housing the solid material.The chamber containing the solid material slowly fills with warm solvent. Some of the desired compound will then dissolve in the warm solvent. When the Soxhlet chamber is almost full, the chamber is automatically emptied by a
siphon side arm, with the solvent running back down to thedistillation flask. This cycle may be allowed to repeat many times, over hours or days.During each cycle, a portion of the non-volatile compound dissolves in the solvent. After many cycles the desired compound is concentrated in the distillation flask. The advantage of this system is that instead of many portions of warm solvent being passed through the sample, just one batch of solvent is recycled.
After extraction the solvent is removed, typically by means of a
rotary evaporator , yielding the extracted compound. The non-soluble portion of the extracted solid remains in the thimble, and is usually discarded.History
William B. Jensen notes ["The Origin of the Soxhlet Extractor" William B. Jensen Vol. 84 No. 12 December 2007 •
Journal of Chemical Education 1913] that the earliest example of a continuous extractor is archaeological evidence for aMesopotamian hot-water extractor for organic matter dating from approximately 3500 BC. Before Soxhlet, the French chemistAnselme Payen also pioneered with continuous extraction in the 1830's.References
Links
* [http://www.campbell.edu/faculty/jung/soxhlet.ppt The Soxhlet Extractor explained.]
* [http://pipeline.corante.com/archives/2008/02/21/new_tricks_with_glassware.php Soxhlet apparatus used as a replenishing source of solvent in chromatography. ]
Wikimedia Foundation. 2010.