Soxhlet attachment
The Soxhlet attachment is an attachment for the continuous extraction of soluble ingredients from solids. He uses the drain siphon principle like a Pythagorean cup to continuously draw off the extract and to extract the extraction material with pure solvent .
history
The Soxhlet apparatus bears the name of its inventor Franz von Soxhlet (1848–1926, Munich), who used it to determine the fat content of dried foods. Franz von Soxhlet mainly worked on the analysis of milk fat. For its extraction with the Soxhlet apparatus, milk powder was first produced in order to remove unwanted water.
functionality
The solid to be extracted is filled into an extraction thimble , which mostly consists of cellulose , but also of glass fibers . In the flask (1) under the Soxhlet attachment, a solvent is heated to the boil, the vapors of which rise through the steam pipe (3) and condense in the reflux condenser (9). The solvent then drips into the extraction thimble (5) and there dissolves the desired substance from the solid.
As the solvent continues to drip in, the liquid level in the Soxhlet attachment rises until it has reached the level of the knee of the lateral siphon tube. The siphon effect that then occurs conveys the extract back into the flask with the solvent. Continuous boiling of the solvent in the flask and condensation in the condenser fills the extraction chamber again and again - the cycle repeats itself. The extraction thimble must be higher than the overflow so that floating particles of the extraction material do not get into the extract. As a result of this constant leaching , also known as percolation , with always pure solvent, the extract dissolved in the solvent increasingly accumulates in the flask. To isolate the extract, the Soxhlet apparatus is dismantled and the contents of the flask are concentrated by evaporating the solvent (e.g. on a rotary evaporator ). The extract remains as a residue.
application
The Soxhlet apparatus is recommended in synthetics when the substance to be extracted is poorly soluble in the extractant, the same applies when natural substances are to be extracted from their sources. In analysis it is also used to determine the fat content of food and feed, as well as to determine the PAH concentration in contaminated soils. At the beginning of the 20th century it was used in child care to determine the fat content of dry milk, which is why it appears in children's literature at this time , for example by Agnes Sapper .
Other methods
There are other extraction methods that are widely used.
- Extraction according to Twisselmann
- Dean-Stark ; a method for measuring liquid saturation in a core sample by distillation extraction. The water in the sample is evaporated by the boiling solvent, then condensed and collected in a calibrated container.
- Likens-Nickerson ; an extraction combined with a distillation for essential oils , but it is labor and time-consuming and not particularly accurate.
- Neo-Clevenger ; also for essential oils, a modification is the “Karlsruher apparatus” and the “Thübinger apparatus”, they are suitable for small quantities.
- Bligh & Dyer ; a quick method for total lipid extraction and processing, but also not particularly accurate.
- Folch ; a widely used method for extracting lipids
- Method according to Victor Meyer ; here the molar mass of a vaporizable liquid can be determined
- Liquid-liquid extraction is used when simpler alternatives such as B. Distillation does not lead to the goal. It is a process for separating one or more components from a solution by dissolving them out with a suitable solvent. It can also be done with the Kutscher-Steudel apparatus .
Web links
Individual evidence
- ^ Brockhaus ABC chemistry. VEB FA Brockhaus Verlag, Leipzig 1965, p. 1312.
- ↑ F. Soxhlet: The weight analysis determination of milk fat. In: Polytechnisches Journal . 232, 1879, pp. 461-465.
- ↑ H. Becker, R. Beckert: Organikum . 23rd edition, Wiley-VCH Verlag, 2009, ISBN 978-3-527-32292-3 , pp. 59-60.
- ↑ LAGA Merkbatt: Requirements for the recycling of mineral residues / waste .