Scheidetrichter zwei Phasen brauner Hintergrund

A separatory funnel, also known as a separation funnel, separating funnel, or colloquially sep funnel, is a piece of

laboratory glassware Laboratory glassware is a variety of equipment used in science, scientific work, traditionally made of glass. Glass may be blown, bent, cut, molded, or formed into many sizes and shapes. It is commonly used in chemistry, biology, and analytical ...

used in liquid-liquid extractions to separate (''partition'') the components of a mixture into two

immiscible Miscibility () is the property of two chemical substance, substances to mix in all mixing ratio, proportions (that is, to fully dissolution (chemistry), dissolve in each other at any concentration), forming a homogeneity and heterogeneity, homoge ...

solvent A solvent (from the Latin language, Latin ''wikt:solvo#Latin, solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a Solution (chemistry), solution. A solvent is usually a liquid but can also be a solid, a gas ...

phases of different densities. Typically, one of the phases will be aqueous, and the other a

lipophilic Lipophilicity (from Greek language, Greek λίπος "fat" and :wikt:φίλος, φίλος "friendly") is the ability of a chemical compound to dissolve in fats, oils, lipids, and non-polar solvents such as hexane or toluene. Such compounds are c ...

organic solvent A solvent (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 p ...

such as

ether In organic chemistry, ethers are a class of compounds that contain an ether group, a single oxygen atom bonded to two separate carbon atoms, each part of an organyl group (e.g., alkyl or aryl). They have the general formula , where R and R� ...

MTBE Methyl ''tert''-butyl ether (MTBE), also known as ''tert''-butyl methyl ether, is an organic compound with a structural formula (CH3)3COCH3. MTBE is a volatile, flammable, and colorless liquid that is sparingly soluble in water. Primarily used as ...

dichloromethane Dichloromethane (DCM, methylene chloride, or methylene bichloride) is an organochlorine compound with the formula . This colorless, volatile liquid with a chloroform-like, sweet odor is widely used as a solvent. Although it is not miscible with ...

chloroform Chloroform, or trichloromethane (often abbreviated as TCM), is an organochloride with the formula and a common solvent. It is a volatile, colorless, sweet-smelling, dense liquid produced on a large scale as a precursor to refrigerants and po ...

, or

ethyl acetate Ethyl acetate commonly abbreviated EtOAc, ETAC or EA) is the organic compound with the formula , simplified to . This flammable, colorless liquid has a characteristic sweet smell (similar to pear drops) and is used in glues, nail polish removers, ...

. All of these solvents form a clear delineation between the two liquids. The more dense liquid, typically the aqueous phase unless the organic phase is

halogenated In chemistry, halogenation is a chemical reaction which introduces one or more halogens into a chemical compound. Halide-containing compounds are pervasive, making this type of transformation important, e.g. in the production of polymers, drugs ...

, sinks to the bottom of the funnel and can be drained out through a valve away from the less dense liquid, which remains in the separatory funnel.

Description

A separating funnel takes the shape of a cone with a hemispherical end. It has a stopper at the top and

stopcock A stopcock is a form of valve used to control the flow of a liquid or gas. The term is not precise and is applied to many different types of valve. The only consistent attribute is that the valve is designed to completely stop the flow when clo ...

(tap), at the bottom. Separating funnels used in laboratories are typically made from

borosilicate glass Borosilicate glass is a type of glass with silica and boron trioxide as the main glass-forming constituents. Borosilicate glasses are known for having very low coefficients of thermal expansion (≈3 × 10−6 K−1 at 20 °C), ma ...

and their taps are made from glass or

PTFE Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene, and has numerous applications because it is chemically inert. The commonly known brand name of PTFE-based composition is Teflon by Chemours, a spin-off fro ...

. Typical sizes are between 30 mL and 3 L. In industrial chemistry they can be much larger and for much larger volumes

centrifuge A centrifuge is a device that uses centrifugal force to subject a specimen to a specified constant force - for example, to separate various components of a fluid. This is achieved by spinning the fluid at high speed within a container, thereby ...

s are used. The sloping sides are designed to facilitate the identification of the layers. The tap-controlled outlet is designed to drain the liquid out of the funnel. On top of the funnel there is a standard taper joint which fits with a ground glass or Teflon stopper. To use a separating funnel, the two phases and the mixture to be separated in solution are added through the top with the stopcock at the bottom closed. The funnel is then closed and shaken gently by inverting the funnel multiple times; if the two solutions are mixed together too vigorously

emulsions An emulsion is a mixture of two or more liquids that are normally immiscible (unmixable or unblendable) owing to liquid-liquid phase separation. Emulsions are part of a more general class of two-phase systems of matter called colloids. Althoug ...

will form. The funnel is then inverted and the stopcock carefully opened to release excess

vapor pressure Vapor pressure or equilibrium vapor pressure is the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases (solid or liquid) at a given temperature in a closed system. The equilibrium vapor pressure is an indicat ...

. The separating funnel is set aside to allow for the complete separation of the phases. The top and the bottom stopcock are then opened and the lower phase is released by

gravitation In physics, gravity (), also known as gravitation or a gravitational interaction, is a fundamental interaction, a mutual attraction between all massive particles. On Earth, gravity takes a slightly different meaning: the observed force b ...

. The top must be opened while releasing the lower phase to allow pressure equalization between the inside of the funnel and the atmosphere. When the bottom layer has been removed, the stopcock is closed and the upper layer is poured out through the top into another container.

Theory

The separating funnel relies on the concept of "like dissolves like", which describes the ability of polar solvents to dissolve polar solutes and non-polar solvents to dissolve non-polar solutes. When the separating funnel is agitated, each solute migrates to the solvent (also referred to as "phase") in which it is more soluble. The solvents normally do not form a unified solution together because they are immiscible. When the funnel is kept stationary after agitation, the liquids form distinct physical layers - lower density liquids will stay above higher density liquids. A mixture of solutes is thus separated into two physically separate solutions, each enriched in different solutes. The stopcock may be opened after the two phases separate to allow the bottom layer to escape the separator funnel. The top layer may be retained in the separating funnel for further extractions with additional batches of solvent or drained out into a separate vessel for other uses. If it is desired to retain the bottom layer in the separating funnel for further extractions, both layers are taken out separately, and then the former bottom layer is returned to the separating funnel. Each independent solution can then be extracted again with additional batches of solvent, used for other physical or chemical processes. If the goal was to separate a soluble material from mixture, the solution containing that desired product can sometimes simply be evaporated to leave behind the purified solute. For this reason, it is a practical benefit to use

volatile solvent A solvent (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 pola ...

s for extracting the desired material from the mixture.

Emulsions

One of the drawbacks of using a separating funnel is

emulsion An emulsion is a mixture of two or more liquids that are normally Miscibility, immiscible (unmixable or unblendable) owing to liquid-liquid phase separation. Emulsions are part of a more general class of two-phase systems of matter called colloi ...

s can form easily, and can take a long time to separate once formed. They are often formed while liquids are being mixed in the separating funnel. This can occur when small droplets are suspended in an aqueous solution. If an emulsion is formed, one technique used to separate the liquids is to slowly swirl the solution in the separating funnel. If the emulsion is not separated by this process, a small amount of saturated saline solution is added ("

salting out Salting out (also known as salt-induced precipitation, salt fractionation, anti-solvent crystallization, precipitation crystallization, or drowning out) is a purification technique that utilizes the reduced solubility of certain molecules in a s ...

"). Research is being done on alternative, more efficient techniques, mostly utilizing stir bars (stirrer bars) to decrease or even eliminate the chance of emulsification, thus decreasing the amount of waiting time.

Safety concerns

The largest risk when using a separating funnel is that of pressure build-up inside it. Pressure accumulates during mixing if a gas evolving reaction or physical change occurs. This problem can be easily handled by simply opening the stopper at the top of the funnel routinely while mixing. More standard procedure is to turn the separating funnel upside down and open the stopcock to release the pressure as often as needed, a step known as 'venting'. The tip of the funnel should be pointed away from the body during venting.Fessenden, J., Joan S. Fessenden, Patty Feist. Organic Laboratory Techniques, 3rd Edition, 2001. Pacific Grove, California: Brooks Cole Publishing, p. 59.

Gallery

File:Separatory funnel-tag.svg, File:Separatory funnel.jpg, The ether layer with a dissolved yellow compound is on top and an aqueous layer is at the bottom File:(09-04-26).1 - 07 (Large).JPG,

Apple An apple is a round, edible fruit produced by an apple tree (''Malus'' spp.). Fruit trees of the orchard or domestic apple (''Malus domestica''), the most widely grown in the genus, are agriculture, cultivated worldwide. The tree originated ...

banana A banana is an elongated, edible fruit – botanically a berry – produced by several kinds of large treelike herbaceous flowering plants in the genus '' Musa''. In some countries, cooking bananas are called plantains, distinguishing the ...

carrot The carrot ('' Daucus carota'' subsp. ''sativus'') is a root vegetable, typically orange in colour, though heirloom variants including purple, black, red, white, and yellow cultivars exist, all of which are domesticated forms of the wild ...

, and

lettuce Lettuce (''Lactuca sativa'') is an annual plant of the family Asteraceae mostly grown as a leaf vegetable. The leaves are most often used raw in Green salad, green salads, although lettuce is also seen in other kinds of food, such as sandwiche ...

extraction using

acetone Acetone (2-propanone or dimethyl ketone) is an organic compound with the chemical formula, formula . It is the simplest and smallest ketone (). It is a colorless, highly Volatile organic compound, volatile, and flammable liquid with a charact ...

, water, and

. Lower layer is the organic layer.

References