Soxhlet extractor

The Soxhlet apparatus (also Soxhlett, Soxhlet ) is an essay for the continuous extraction of soluble constituents from solids.

History

The Soxhlet apparatus is named after its inventor Franz von Soxhlet (1848-1926, Munich), the resulting measuring the fat content of dried foods. Franz von Soxhlet worked mainly on the analysis of milk fat. For the extraction with the Soxhlet extractor, first the milk powder was prepared to remove disturbing water.

Operation

The to be extracted solid was poured into an extraction thimble, usually a short, open on one side cellulose tube that is inserted into the Soxhlet apparatus. In the piston (1) under the Soxhlet apparatus, a solvent is heated to boiling. Its vapors rise through the steam pipe ( 3) and condense in the cooler (9 ) above. The solvent drips into the extraction thimble ( 5) and triggers the desired substance from the solid out.

By further zutropfendes solvent of the liquid level rises in a Soxhlet apparatus until it reaches the height of the bend of the thin tube (6). The siphon then occurring promotes extract back into the flask with the solvent. Continuous boiling of the solvent in the flask and condense on the cooler fills the extraction chamber always again - the cycle repeats itself. This dissolved in the solvent extract accumulates more and more in the piston. For isolating the extract, the Soxhlet apparatus is dismantled and the contents of the flask concentrated by evaporation of the solvent ( for example in a rotary evaporator ). Remains as residue of the extract.

Application

The Soxhlet apparatus is recommended in the synthetic if you want to extract the substance is poorly soluble in the extractant. In the analysis it is also used for determining the fat content of food and feed, as well as for the determination of PAH in contaminated soils. At the beginning of the 20th century it was used in child care for the determination of the fat content of dried milk, therefore it appeared at that time in children's literature on, for example, Agnes Sapper.