Soxhlet extractor

Short description: Laboratory apparatus

A schematic representation of a Soxhlet extractor:

1. Stirrer bar
2. Still pot (the still pot should not be overfilled and the volume of solvent in the still pot should be 3 to 4 times the volume of the Soxhlet chamber)
3. Distillation path
4. Thimble
5. Solid
6. Siphon top
7. Siphon exit
8. Expansion adapter
9. Condenser
10. Cooling water out
11. Cooling water in

A Soxhlet extractor is a piece of laboratory apparatus[1] invented in 1879 by Franz von Soxhlet.[2] It was originally designed for the extraction of a lipid from a solid material. Typically, Soxhlet extraction is used when the desired compound has a limited solubility in a solvent, and the impurity is insoluble in that solvent. It allows for unmonitored and unmanaged operation while efficiently recycling a small amount of solvent to dissolve a larger amount of material.

## Contents

* 1 Description
* 2 Assembly
* 3 Operation
* 4 History
* 5 Gallery
* 6 References
* 7 External links

## Description

A Soxhlet extractor has three main sections: a percolator (boiler and reflux) which circulates the solvent, a thimble (usually made of thick filter paper) which retains the solid to be extracted, and a siphon mechanism, which periodically empties the condensed solvent from the thimble back into the percolator.

## Assembly

* The source material containing the compound to be extracted is placed inside the thimble.

* The thimble is loaded into the main chamber of the Soxhlet extractor.
* The extraction solvent to be used is placed in a distillation flask.
* The flask is placed on the heating element.
* The Soxhlet extractor is placed atop the flask.
* A reflux condenser is placed atop the extractor.

## Operation

The solvent is heated to reflux. The solvent vapour travels up a distillation 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 dissolves in the cold solvent. When the Soxhlet chamber is almost full, the chamber is emptied by the siphon. The solvent is returned to the distillation flask. The thimble ensures that the rapid motion of the solvent does not transport any solid material to the still pot. 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. Like Soxhlet extractor, the Kumagawa extractor has a specific design where the thimble holder/chamber is directly suspended inside the solvent flask (having a vertical large opening) above the boiling solvent. The thimble is surrounded by hot solvent vapour and maintained at a higher temperature compared to the Soxhlet extractor, thus allowing better extraction for compounds with higher melting points such as bitumen. The removable holder/chamber is fitted with a small siphon side arm and, in the same way as for Soxhlet, a vertical condenser ensures that the solvent drips back down into the chamber which is automatically emptied at every cycle.

## History

William B. Jensen notes that the earliest example of a continuous extractor is archaeological evidence for a Mesopotamian hot-water extractor for organic matter dating from approximately 3500 BC.[3] The same mechanism is present in the Pythagorean cup. Before Soxhlet, the French chemist Anselme Payen also pioneered with continuous extraction in the 1830s.

A Soxhlet apparatus has been proposed as an effective technique for washing mass standards.[4]

## Gallery

* Animation of Soxhlet extractor at work

* Fruit extraction in progress. The sample is placed directly in the extraction chamber, no thimble used.

* The siphoning part of a Soxhlet extraction.

## References

1. ↑ Harwood, Laurence M.; Moody, Christopher J. (13 Jun 1989). Experimental organic chemistry: Principles and Practice (Illustrated ed.). Wiley-Blackwell. pp. 122–125. ISBN 978-0-632-02017-1. https://archive.org/details/experimentalorga00harw/page/122.
2. ↑ Soxhlet, F. (1879). "Die gewichtsanalytische Bestimmung des Milchfettes" (in German). Dingler's Polytechnisches Journal 232: 461–465. http://dingler.culture.hu-berlin.de/article/pj232/ar232136.
3. ↑ Jensen, William B. (December 2007). "The Origin of the Soxhlet Extractor". Journal of Chemical Education 84 (12): 1913–1914. doi:10.1021/ed084p1913. Bibcode: 2007JChEd..84.1913J.
4. ↑ Cumpson, Peter; Sano, Naoko (February 2013). "Stability of reference masses V: UV/ozone treatment of gold and platinum surfaces". Metrologia 50 (1): 27–36. doi:10.1088/0026-1394/50/1/27. Bibcode: 2013Metro..50...27C. "The apparatus we propose for the solvent pre-wash is the Soxhlet apparatus, which has been used very successfully before for washing stainless-steel standard-mass surfaces. This apparatus has its main application in chemistry for dissolving weakly soluble species from solid matrices.".

## External links

* The Soxhlet Extractor explained
* Royal Society of Chemistry: Classic Kit: Soxhlet extractor
* Soxhlet apparatus used as a replenishing source of solvent in chromatography
* Extracting the Spicy Chemical in Black Pepper video demonstrating the use of a Soxhlet extractor to extract piperine from black pepper.
* thimbles used for Soxhlet extraction

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Laboratory equipment

General

* Heaters
* Dryers

* Alcohol burner
* Bunsen burner
* Desiccator
* Heating mantle
* Hot plate
* Lab oven
* Kiln
* Meker–Fisher burner
* Striker
* Teclu burner
* Water bath
* Vacuum dry box

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* Mixers
* Shakers

* Chemostat
* Homogenizer
* Liquid whistle
* Magnetic stirrer
* Mortar and pestle
* Shaker
* Sonicator
* Static mixer
* Stirring rod
* Vortex mixer
* Wash bottle

* Stands
* Clamps
* Holders

* Beaker clamp
* Clamp holder
* Tripod
* Burette clamp
* Extension clamp
* Flask clamp
* Funnel support
* Iron ring
* Pinch clamp
* Retort stand
* Screw clamp
* Test tube holder
* Test tube rack
* Wire gauze
* Lab drying rack

* Containers
* Storage

* Agar plate
* Cryogenic storage dewar
* Incubator
* Laminar flow cabinet
* Microtiter plate
* Petri dish
* Picotiter plate
* Refrigerator
* Weighing boat
* Weighing dish

Other items|

* Aspirator
* Autoclave
* Balance brush
* Cork borer
* Crucible
* Filter paper
* File
* Forceps
* Centrifuge
* Microscope
* Pipeclay triangle
* Spectrophotometer
* Splint
* Stopper
* Scoopula
* Spatula
* Test tube brush
* Wire brush
* Inoculation needle
* Inoculation loop

Glassware

| Apparatus|

* Dean–Stark
* Soxhlet extractor
* Kipp's

|

Bottles|

* Boston round
* Pycnometer

Condensers|

* Cold finger
* Liebig

Dishes|

* Evaporating
* Petri
* Syracuse
* Watch glass

Flasks|

* Büchner
* Vacuum (Dewar)
* Erlenmeyer
* Fernbach
* Fleaker
* Florence
* Retort
* Round-bottom
* Schlenk
* Volumetric

Funnels|

* Büchner
* Hirsch
* Dropping
* Separatory

Measuring devices|

* Burette
* Conical measure
* Cuvette
* Eudiometer
* Graduated cylinder
* Ostwald viscometer
* Pipette
* Pipette (dropper)

Tubes|

* Boiling
* Drying
* Cragie
* Ignition
* Nuclear magnetic resonance (NMR)
* Test
* Thiele
* Thistle

Other items|

* Beaker
* Bell jar
* Gas syringe
* Vial

Analytical chemistry

| Compositional|

* AutoAnalyzer
* CHN analyzer
* Colorimeter
* Inductively coupled plasma (ICP) device
* Gas chromatograph (GC)
* Liquid Chromatograph (LC)
* Mass spectrometer (MS)
* pH indicator
* pH meter

|

Microscopy|

* Scanning electron microscope (SEM)
* Transmission electron microscope (TEM)

Thermochemistry|

* Calorimeter
* differential scanning
* Melting-point apparatus
* Thermometer
* Thermogravimetric analyzer (TGA)

Other items|

* Analytical balance
* Colony counter
* Spiral plater
* Nuclear magnetic resonance (NMR) instrument
* Plate reader

Electronics

* Ammeter
* Current source
* Function generator
* Galvanostat
* Multimeter
* Network analyzer
* Oscilloscope
* Pulse generator
* Potentiostat
* Spectrum analyzer
* Time-domain reflectometer
* Voltage source
* Voltmeter

Safety

Personal protective
equipment (PPE)

* Lab coat
* Face shield
* Respirator
* Rubber apron
* Safety shower

Eye and hand|

* Acid-resistant gloves
* Eyewash station
* Glove box
* Medical gloves
* Nitrile gloves
* Safety glasses
* Safety goggles

Other items|

* Acid (solvent) cabinet
* Biosafety cabinet
* Fire blanket
* Fire extinguisher
* Fume hood

Instruments used in medical laboratories

* v
* t
* e

Distillation

Principles|

* Raoult's law
* Dalton's law
* Reflux
* Fenske equation
* McCabe–Thiele method
* Theoretical plate
* Partial pressure
* Vapor–liquid equilibrium

Industrial processes|

* Batch distillation
* Continuous distillation
* Fractionating column
* Spinning cone

Laboratory methods|

* Alembic
* Kugelrohr
* Rotary evaporator
* Spinning band distillation
* Still

Techniques|

* Azeotropic
* Catalytic
* Destructive
* Dry
* Extractive
* Fractional
* Reactive
* Salt-effect
* Steam-based
* Vacuum-based

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