======Using a Separating Funnel======


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**Alternative titles:** Liquid–Liquid Extraction
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====Summary====                   
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====Procedure====  
  - Clamp the separatory funnel securely by the neck; ensure the stopcock is closed and place a labeled receiving flask beneath the stem.
  - Add the first liquid phase to the funnel, then add the second immiscible phase (commonly, organic solvent and water). Insert the stopper firmly.
  - Support the stopper with one hand and the stopcock with the other; invert the funnel and gently swirl to mix.
  - Vent immediately by opening the stopcock while the funnel is inverted and pointed away from people and equipment; close and repeat a mix–vent cycle several times.
  - Return the funnel to the ring stand and allow the layers to separate fully (wait until a sharp interface forms).
  - Identify which layer is which: compare known densities, or add a drop of water—if the drop joins the lower layer, the lower layer is aqueous.
  - Drain the bottom layer slowly into a labeled flask, stopping just before the interface reaches the stopcock.
  - Remove the funnel from the clamp and pour the top layer out of the top into a second labeled flask to avoid contaminating it with residual bottom-layer hold-up in the stopcock channel.
  - For improved recovery, perform multiple small-volume extractions rather than a single large one; combine like layers as appropriate.
  - Dry the organic layer if needed by adding a suitable anhydrous drying agent (e.g., magnesium sulfate or calcium chloride), swirl, wait a few minutes, and decant or filter off the dry solution.




====Links==== 
Using a Separating Funnel - Cormac Quigley: 
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How to Use a Separatory Funnel - Chemistry in a Nutshell: 
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====Variations====
  * Demonstrate an extraction with colored solutes (e.g., iodine in an organic solvent, then extract into aqueous iodide) to visualize partitioning.
  * Show “salting out” by adding sodium chloride to the aqueous phase to reduce emulsion formation and shift distribution.
  * Run a microscale version in a centrifuge tube with a Pasteur pipette as a mini-separator for rapid trials.
  * Quantify extraction efficiency by measuring color intensity or absorbance of each layer and comparing single vs. multiple extractions.



====Safety Precautions====
  * Wear splash goggles, lab coat, and appropriate chemical-resistant gloves; conduct work in a fume hood when using volatile or hazardous solvents.
  * Always vent the funnel away from people—pressure can build rapidly with volatile solvents or acid/base reactions.
  * Keep a firm grip on the stopper and stopcock while shaking; do not clamp the funnel while shaking.
  * Check that the stopcock is closed before filling and that all joints are secure to prevent spills.
  * Dispose of waste properly (e.g., segregate halogenated and non-halogenated organic waste; never pour organic solvents down the drain).




====Questions to Consider====
  * Why is venting necessary during shaking? (Mixing can generate vapor pressure or gases; venting prevents dangerous pressure buildup.)
  * How can you confirm which layer is the aqueous layer? (Compare densities or add a drop of water to see which layer it joins.)
  * Why are several small extractions more effective than one large extraction with the same total volume? (Partitioning is governed by the distribution coefficient; multiple contacts extract a greater fraction overall.)
  * What causes emulsions and how can you break them? (Fine dispersions form from vigorous mixing or surfactants; allow time, add salt, gently swirl, or use a small amount of a mutually soluble solvent.)
  * Why dry the organic layer before evaporation? (Dissolved water carries impurities and can reduce yield or purity; drying agents remove residual moisture.)