A separatory funnel, also known as separation funnel, separating funnel, or colloquially sep funnel, is a piece of laboratory glassware used in liquid-liquid extraction

Liquid-liquid extraction

Liquid–liquid extraction, also known as solvent extraction and partitioning, is a method to separate compounds based on their relative solubilities in two different immiscible liquids, usually water and an organic solvent. It is an extraction of a substance from one liquid phase into another liquid...

s to separate (partition) the components of a mixture between two immiscible solvent

Solvent

A solvent is a liquid, solid, or gas that dissolves another solid, liquid, or gaseous solute, resulting in a solution that is soluble in a certain volume of solvent at a specified temperature...

 phases of different densities

Density

The mass density or density of a material is defined as its mass per unit volume. The symbol most often used for density is ρ . In some cases , density is also defined as its weight per unit volume; although, this quantity is more properly called specific weight...

 Typically, one of the phases will be aqueous, and the other a non-polar lipophilic

Lipophilic

Lipophilicity, , refers to the ability of a chemical compound to dissolve in fats, oils, lipids, and non-polar solvents such as hexane or toluene. These non-polar solvents are themselves lipophilic — the axiom that like dissolves like generally holds true...

 organic solvent such as ether

Ether

Ethers are a class of organic compounds that contain an ether group — an oxygen atom connected to two alkyl or aryl groups — of general formula R–O–R'. A typical example is the solvent and anesthetic diethyl ether, commonly referred to simply as "ether"...

, MTBE, dichloromethane

Dichloromethane

Dichloromethane is an organic compound with the formula CH2Cl2. This colorless, volatile liquid with a moderately sweet aroma is widely used as a solvent. Although it is not miscible with water, it is miscible with many organic solvents...

, chloroform

Chloroform

Chloroform is an organic compound with formula CHCl3. It is one of the four chloromethanes. The colorless, sweet-smelling, dense liquid is a trihalomethane, and is considered somewhat hazardous...

, or ethyl acetate

Ethyl acetate

Ethyl acetate is the organic compound with the formula CH3COOCH2CH3. This colorless liquid has a characteristic sweet smell and is used in glues, nail polish removers, and cigarettes...

. All of these solvents form a crisp delineation between the two liquids. The two layers formed are usually known as the organic and aqueous phase. Most organic solvents float on top of an aqueous phase, though important exceptions are most halogen

Halogen

The halogens or halogen elements are a series of nonmetal elements from Group 17 IUPAC Style of the periodic table, comprising fluorine , chlorine , bromine , iodine , and astatine...

ated solvent

Solvent

A solvent is a liquid, solid, or gas that dissolves another solid, liquid, or gaseous solute, resulting in a solution that is soluble in a certain volume of solvent at a specified temperature...

s. The organic solvent used for the extraction must not react with the substance to be extracted and with water. As well it should also have a low boiling point so it can be easily removed from the product.

A separating funnel has the shape of a cone surmounted by a hemisphere. It has a stopper at the top and stopcock

Stopcock

A stopcock is a valve used to restrict or isolate the flow of a liquid or gas through a pipe.In Great Britain a stopcock, not to be confused with a gate valve or a DiCiaccio branch, is used to prevent flow of water into a domestic water system. There are usually two stopcocks for a home...

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

Borosilicate glass

Borosilicate glass is a type of glass with the main glass-forming constituents silica and boron oxide. Borosilicate glasses are known for having very low coefficients of thermal expansion , making them resistant to thermal shock, more so than any other common glass...

 and their stopcocks are made from glass or PTFE

Polytetrafluoroethylene

Polytetrafluoroethylene is a synthetic fluoropolymer of tetrafluoroethylene that finds numerous applications. PTFE is most well known by the DuPont brand name Teflon....

. Typical sizes are between 50 mL and 3 L. In industrial chemistry they can be much bigger and for much larger volumes centrifuge

Centrifuge

A centrifuge is a piece of equipment, generally driven by an electric motor , that puts an object in rotation around a fixed axis, applying a force perpendicular to the axis...

s are used. The sloping sides are designed to facilitate the identification of the layers. The stopcock-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 separatory 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 will form. The funnel is then inverted and the tap carefully opened to release excess vapor pressure

Vapor pressure

Vapor pressure or equilibrium vapor pressure is the pressure of a vapor in thermodynamic equilibrium with its condensed phases in a closed system. All liquids have a tendency to evaporate, and some solids can sublimate into a gaseous form...

. The separating funnel is set aside to allow for the complete separation of the phases. The top and the bottom tap are then opened and the two phases are released by gravitation.

Before using the separatory funnel, make sure it is placed safely in a ring stand. As well place an Erlenmeyer flask below the separatory funnel to ensure that any drops which may leak out of the funnel be caught in the flask. Finally, it is of vital importance to make sure that the stopcock is tightly closed.

Emulsions

The Emulsions can be formed meanwhile the solutions or liquids are being mixed in the separatory funnel. This occurs when a small droplet is suspended in a water solution. These can be difficult to disperse. Once the emulsions are formed, try to slowly swirl the solution in the separatory funnel. If the emulsions are not evenly eliminated, then try to add a small amount of aqueous sodium chloride.

See also

• Dropping funnel
  Dropping funnel
  A dropping funnel is a type of laboratory glassware used to transfer fluids. They are fitted with a stopcock which allows the flow of to be controlled. Dropping funnels are useful for adding reagents slowly, i.e. drop-wise...
  
  s are similar in shape and design, and may be used as separatory funnels. They have standard taper ground glass joints at the stem.