A Soxhlet extractor is a piece of

laboratory A laboratory (; ; colloquially lab) is a facility that provides controlled conditions in which scientific or technological research, experiments, and measurement may be performed. Laboratory services are provided in a variety of settings: physi ...

apparatus invented in 1879 by Franz von Soxhlet. It was originally designed for the extraction of a

lipid Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids in ...

from a solid material. Typically, Soxhlet extraction is used when the desired compound has a ''limited''

solubility In chemistry, solubility is the ability of a substance, the solute, to form a solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form such a solution. The extent of the solubi ...

in a

solvent A solvent (s) (from the Latin '' solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a solution. A solvent is usually a liquid but can also be a solid, a gas, or a supercritical fluid. Water is a solvent for ...

, and the impurity is

insoluble In chemistry, solubility is the ability of a substance, the solute, to form a solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form such a solution. The extent of the solubi ...

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.

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 thimble.

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

to be used is placed in a distillation

flask Flask may refer to: Container * Hip flask, a small container used to carry a small amount of liquid * Laboratory flask, laboratory glassware for holding larger volumes than simple test tubes ** Erlenmeyer flask, a common laboratory flask wit ...

. # The flask is placed on the

heating element A heating element converts electrical energy into heat through the process of Joule heating. Electric current through the element encounters resistance, resulting in heating of the element. Unlike the Peltier effect, this process is indepen ...

. # 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 Distillation, or classical distillation, is the process of separating the components or substances from a liquid mixture by using selective boiling and condensation, usually inside an apparatus known as a still. Dry distillation is the he ...

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 warm solvent. When the Soxhlet chamber is almost full, the chamber is emptied by the

siphon A siphon (from grc, σίφων, síphōn, "pipe, tube", also spelled nonetymologically syphon) is any of a wide variety of devices that involve the flow of liquids through tubes. In a narrower sense, the word refers particularly to a tube in a ...

. The solvent is returned to the

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 A rotary evaporator (rotovap) is a device used in chemical laboratories for the efficient and gentle removal of solvents from samples by evaporation. When referenced in the chemistry research literature, description of the use of this technique and ...

, yielding the extracted compound. The non-soluble portion of the extracted solid remains in the thimble, and is usually discarded.

Kumagawa extractor

Very similar to the 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 Asphalt, also known as bitumen (, ), is a sticky, black, highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term a ...

. 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 Mesopotamia ''Mesopotamíā''; ar, بِلَاد ٱلرَّافِدَيْن or ; syc, ܐܪܡ ܢܗܪ̈ܝܢ, or , ) is a historical region of Western Asia situated within the Tigris–Euphrates river system, in the northern part of the F ...

hot-water extractor for organic matter dating from approximately 3500 BC. The same mechanism is present in the

Pythagorean cup A Pythagorean cup (also known as a Pythagoras cup, Greedy Cup, Cup of Justice or Tantalus cup) is a practical joke device in a form of a drinking cup, credited to Pythagoras of Samos. When it is filled beyond a certain point, a siphoning effect ...

. Before Soxhlet, the French chemist

Anselme Payen Anselme Payen (; 6 January 1795 – 12 May 1871) was a French chemist known for discovering the enzyme diastase, and the carbohydrate cellulose. Biography Payen was born in Paris. He began studying science with his father when he was a 13-ye ...

also pioneered with continuous extraction in the 1830s. A Soxhlet apparatus has been proposed as an effective technique for washing mass standards.

References

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 Piperine, along with its isomer chavicine, is the alkaloid responsible for the pungency of black pepper and long pepper. It has been used in some forms of traditional medicine. Preparation Due to its poor solubility in water, piperine is typi ...

from black pepper.
thimbles used for Soxhlet extraction
{{DEFAULTSORT:Soxhlet Extractor Laboratory glassware Laboratory techniques Analytical chemistry Articles containing video clips Laboratory equipment