A separatory funnel, also known as separation funnel, separating funnel, or colloquially sep funnel, is a piece of laboratory glassware used in liquid-liquid extractions to separate (partition) the components of a mixture between two immiscible solvent phases of different densities[1] Typically, one of the phases will be aqueous, and the other a non-polar lipophilic organic solvent such as ether, MTBE, dichloromethane, chloroform, or ethyl acetate. All of these solvents form a crisp delineation between the two liquids. [2]The two layers formed are usually known as the organic and aqueous phase. [3] Most organic solvents float on top of an aqueous phase, though important exceptions are most halogenated solvents. [4]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. [5]
A separating funnel has the shape of a cone surmounted by a hemisphere. It has a stopper at the top and stopcock (tap), at the bottom. Separating funnels used in laboratories are typically made from borosilicate glass and their stopcocks are made from glass or PTFE. Typical sizes are between 50 mL and 3 L. In industrial chemistry they can be much bigger and for much larger volumes centrifuges 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. [6]
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. 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. [7]
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. [8]
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