Separatory Funnels: How They Work and Where They’re Used
A practical guide to liquid layers, controlled draining, and choosing between Viking Lab Supply’s 1 L and 2 L borosilicate funnels.
A separatory funnel turns a familiar observation—some liquids form separate layers—into a useful laboratory technique. The glass body lets you watch the boundary between those layers, while the stopcock lets you collect the lower liquid without pouring everything into the same container.
The interesting part happens before draining. A dissolved substance can redistribute between two liquid phases. That makes the funnel useful for moving a compound into another solvent, washing away soluble impurities, or preparing a sample for analysis.
Actual product photograph from Viking Lab Supply’s listing. The pictured funnel is marked 2000 mL.
The transparent body makes the interface visible; the valve controls collection. Verify the selected variant’s parts and specifications before ordering.
1. Two different jobs: separating and extracting
Separating bulk liquids means allowing two immiscible liquids to settle, then collecting them separately. Cooking oil and water offer a visible example: after the droplets coalesce, the oil usually sits above the water.
Liquid–liquid extraction goes further. A dissolved compound distributes between two phases according to its affinity for each. Mixing increases contact between the liquids; settling restores a boundary so the phases can be collected. A compound need not move completely into one layer for the extraction to be useful.
Think of two questions separately: Which layer sits on the bottom? depends on density. Which layer contains the substance of interest? depends on distribution chemistry. Knowing one does not answer the other. [2]
Aqueous: a water-based phase. Organic: a phase based on an organic solvent; the word does not imply food certification or safety. Interface: the boundary between phases. Wash: contacting a retained phase with another liquid to remove unwanted components.
2. Know the parts before adding liquid
The stopper closes the mouth during hand-held mixing. It must fit the specific neck; nominal funnel capacity alone does not identify the correct stopper. The stopcock controls drainage. PTFE plugs commonly operate without stopcock grease, but assembly, seals, and adjustment must follow the supplied instructions. [3]
The support matters as much as the glass. Use a stable laboratory stand with a correctly sized, cushioned support ring or purpose-built holder. Support the body without squeezing it or placing the load on the drain stem. Place a suitable borosilicate collection beaker underneath before filling. [4]
Build the support setup: stand, ring, and clamp hardware
The funnel is only one part of a usable separation setup. Start with a stable stand, select a ring that supports the funnel body, and leave enough vertical clearance for the valve, drain stem, and collection vessel. These VLS product links let you compare the components before assembling the system.
| VLS component | Role in the setup | Check before use |
|---|---|---|
| 27 Inch Lab Stand for Laboratories | Base and vertical rod for positioning the support hardware. | Rod diameter, usable height, base stability, and the load of the complete filled assembly. |
| Support Ring Lab Equipment | A correctly sized, cushioned ring supports the funnel body while it settles and drains. | Internal ring diameter, funnel-body fit, appropriate cushioning, mounting connection, and supported load. |
| Precision Boss Head Clamp | Connects a compatible clamp or plain support rod to the stand when that mounting arrangement requires it. | Both rod diameters and secure engagement. A ring with its own integral stand clamp may not need a separate boss head. |
| 3 Finger Lab Clamp (Screw) | Optional secondary stabilization only where the funnel and clamp manufacturers permit the contact location and configuration. | Jaw opening, compatible protective coating, mounting hardware, and permission for the intended glass contact. Do not substitute it for a properly fitted support ring without documented suitability. |
| Borosilicate Glass Beakers — Multiple Sizes | Separate, labeled receivers for hydrosol, oil-rich fractions, and any uncertain interface collection. | Capacity for the full collected fraction, stability, chemical compatibility, and adequate clearance below the tip. |
A three-finger clamp is not automatically a separatory-funnel holder. Do not squeeze the bulb, clamp the stopcock, or support the funnel by its narrow drain stem. If the documented setup permits a secondary clamp, use the specified contact area and gentle adjustment to limit movement without stressing the glass. Remove the funnel from its support for hand-held mixing and venting.
Confirm the actual component dimensions and load suitability with VLS before treating these items as a matched assembly. The public listings do not establish a tested compatibility rating for a filled 1 L or 2 L funnel.
3. Where separatory funnels earn their place
Environmental laboratories: preparing water samples
Testing instruments usually need a prepared sample rather than a bottle of untreated water. EPA Method 3510C describes separatory-funnel extraction of water-insoluble and slightly water-soluble organic compounds from aqueous samples. It transfers appropriate analytes into an extract that can undergo additional preparation and analysis. Buying the glassware does not, by itself, establish method compliance: the full method, quality controls, solvent choice, and laboratory procedures still apply. [5]
Chemical research: washing a reaction mixture
After a reaction, a useful compound may be dissolved alongside water-soluble residues. An appropriate aqueous wash can move some unwanted components out of the retained organic phase. The funnel provides visual control over that separation. A successful wash can improve the next step, but it does not certify purity or eliminate the need for analytical checks. [2]
Botanical and formulation development: evaluating phase behavior
As an illustrative workflow, a lab developing a botanical formulation may need to determine whether a liquid preparation forms a separate water-rich layer, or whether an approved wash removes an unwanted soluble component. A separatory funnel can help examine that behavior at bench scale. This is a use of the underlying separation principle, not a validated recipe for a particular botanical product.
Do not confuse this with extracting solids directly. A funnel is poorly suited to a slurry of leaves, bark, or fine powder: solids can block the valve and obscure the interface. Solid–liquid extraction and clarification are separate operations before a suitable liquid–liquid step.
Teaching laboratories: seeing chemistry happen
Students can connect three ideas in one transparent vessel: immiscibility creates two phases, density establishes their vertical order, and solubility influences where a dissolved substance goes. Labeling both collections makes the exercise as much about careful observation and recordkeeping as glassware handling.
Botanical example: mint, rosemary, and lavender hydrosols
After steam distillation or hydrodistillation, the condensate may contain a visible oil phase alongside an aromatic water phase, commonly called a hydrosol. A separatory funnel can be useful at two different stages: collecting an already separate oil layer, and carrying out a solvent extraction of selected aromatic compounds remaining in the water.
Route A: cooled water, gravity, and the stopcock—no extraction solvent
For mint, rosemary, or lavender distillate that already contains a separate free-oil phase, the simplest approach uses the cooled oil-and-water mixture itself. No hexane is needed to collect oil that has already separated from the hydrosol. The funnel is acting as a controlled decanter: gravity establishes the layers, and the valve determines which liquid leaves first.
“Cold-water separation” here means letting cooled condensate settle. Adding cold water to plant material does not reproduce steam distillation, and cooling a clear hydrosol does not guarantee that its dissolved aromatics will form a recoverable oil layer. Lower temperatures can also change viscosity or cause some constituents to crystallize, so use the conditions specified for the material rather than assuming colder is always better.
- Cool the condensate before loading. Bring the collected oil-and-water distillate to the temperature allowed by the method. Do not load a hot distillate or thermally shock the glass with ice water.
- Set up for a gentle separation. Close the valve, support the funnel securely on a correctly fitted support ring and stand, and place a labeled hydrosol collection beaker below it. Pour in the cooled mixture without vigorous shaking, which can disperse oil into small droplets.
- Let a clear boundary develop. Leave the funnel upright, with its stopper removed, and allow the free oil to coalesce. Mint, rosemary, and lavender oils commonly form an upper layer over water, but confirm the actual batch rather than treating that as universal.
- Drain the water-rich lower layer. When the oil is confirmed on top, open the stopcock gradually. Watch the interface move downward as hydrosol collects in the receiver.
- Slow down before the oil reaches the valve. Close the stopcock at the boundary. Preserve a small uncertain interface fraction separately if needed, then collect the retained oil through the mouth into a different, labeled vessel.
- Check both fractions. Look for carried-over water or oil droplets and follow the laboratory’s method for any further separation, drying, or analysis. If the oil is actually the lower phase, reverse the collection plan and collect that identified oil phase first.
A very thin oil film can be difficult to recover in a large funnel. Match the vessel to the actual oil quantity; a smaller separator or purpose-built essential-oil receiver may reduce handling losses. This is one reason a 2 L funnel is not automatically the best choice for a small distillation.
Route B: extract some remaining aromatics with hexane
When the objective is to recover selected dissolved or dispersed aromatic compounds, laboratory-grade hexane can serve as a separate, nonpolar liquid phase. The compounds distribute between the hydrosol and the solvent. The funnel then separates the two bulk liquids; it does not turn all hydrosol constituents into oil or recover every aroma compound equally.
Published rosemary research used n-hexane to prepare hydrosol aroma extracts for GC–MS analysis. This supports the extraction principle, but a small analytical preparation is not a validated production method for a 1 L or 2 L funnel. A separate lavender study investigated other extraction solvents, illustrating that solvent selection changes what is recovered. [9] [10]
n-Hexane has a specific gravity of about 0.66 and very low water solubility, so a hexane-rich phase normally floats above a water-rich hydrosol. Commercial products labeled “hexane” may contain a mixture of isomers; consult the exact supplier’s SDS. [11]
How the funnel fits into the workflow
- Define the objective. Decide whether the task is bulk oil separation, analytical sampling, or process development. Record the botanical identity, batch, and starting hydrosol volume.
- Prepare the liquid. Cool the condensate and address solids or persistent emulsions using the approved method. Recover a separate free-oil layer first if that is the intended product.
- Choose capacity for both phases. Count the hydrosol plus the added solvent and any other liquids. Use the VLS 1 L or 2 L option only when the combined volume, headspace, support, and handling requirements fit.
- Contact and separate. Under an established solvent-handling procedure, mix and vent as described in the main technique section, then allow the phases to settle. Remove the stopper before draining. Collect the lower water-rich phase separately and retain the identified hexane-rich phase.
- Continue under the method. Additional fresh-solvent contacts may improve recovery of some compounds. The solvent ratio and number of contacts must be developed for the actual hydrosol; this guide does not prescribe one universal recipe.
- Recover solvent and verify the extract. Any subsequent drying or solvent removal requires appropriate laboratory equipment and a validated process. Verify composition and residual solvent against the intended product specification before release or use.
| Botanical example | Useful teaching point | What the guide does not assume |
|---|---|---|
| Mint | Use the batch to compare visible free oil with aroma compounds remaining in the water-rich phase. | All mint species have the same chemical profile, or all mint aromatics transfer completely to hexane. |
| Rosemary | Published work demonstrates n-hexane preparation of hydrosol aroma fractions for analysis. | An analytical method proves economical production-scale recovery. |
| Lavender | Compare how solvent choice influences the recovered aromatic fraction. | A solvent extract has the same composition as the original distilled essential oil. |
Mint is an illustrative application of the liquid–liquid principle, not a plant-specific recovery claim. Species, chemotype, distillation conditions, and storage can all affect the starting material.
Hexane is highly flammable; n-hexane exposure can damage the peripheral nervous system. Work in a suitable laboratory fume hood with ignition sources controlled and solvent-compatible protective equipment. Do not boil it off in an open room, use a household heat source, or heat it in a closed funnel. [11]
A clear appearance or lack of solvent odor does not establish acceptable residual hexane. Solvent-contacted hydrosol also requires evaluation and cannot simply be returned to cosmetic, food, or other consumer use. Describe the recovered material accurately as a hydrosol-derived solvent extract until identity, composition, and residual-solvent results support any more specific claim.
4. Choosing a Viking Lab Supply funnel: 1 L or 2 L?
Viking Lab Supply’s public Borosilicate Glass Separatory Funnels listing offers 1 L and 2 L capacity options and describes PTFE stopcocks. Verify the selected variant’s specifications and availability before ordering. Exact joint size, included accessories, dimensions, and solvent compatibility should be confirmed for that variant rather than inferred from a general description. [1]
| Decision | 1 L option | 2 L option |
|---|---|---|
| Best starting question | Will the combined liquids fit with the headspace required by the procedure? | Does a larger combined batch justify the added size and handling load? |
| Conservative planning example* | 300 mL sample + 150 mL solvent = 450 mL combined | 600 mL sample + 300 mL solvent = 900 mL combined |
| Support and handling | Check ring diameter, stand stability, and receiving-vessel clearance. | Check the same factors plus comfortable control of the heavier filled vessel. |
| Small samples | May still be oversized for a small analytical sample. | Extra capacity does not automatically improve recovery or control. |
*Illustrative arithmetic, not manufacturer working limits or validated extraction recipes. Both examples remain below half the nominal capacity as an editorial planning choice. Follow the actual procedure and manufacturer’s limits; gas-generating or difficult mixtures may require more headspace or another method.
Count every liquid present at once: sample, extraction solvent, wash, and any other additions. A “1 L funnel” does not mean that a 1 L sample plus additional solvent is a suitable load. Also consider density: equal liquid volumes can produce very different filled weights.
5. Identify the layers—never guess from color
Water is not automatically the lower layer. Some organic solvents are less dense than an aqueous phase; others are denser. Dissolved salts, temperature, and solvent composition can change the comparison. Predict the order using the actual system, then confirm it with a test permitted by your procedure. [2]
For a compatible system, a small water-drop test can help identify the aqueous phase by observing where the drop merges. Do not add water to an unknown or water-reactive mixture. Until identity is confirmed, label vessels “upper layer” and “lower layer,” together with the sample ID and collection step.
Premature disposal turns a reversible labeling mistake into a lost sample. Retain fractions in compatible, labeled containers under the laboratory’s storage rules.
6. A careful operating workflow
This is a technique overview for trained laboratory work. Select solvents, quantities, mixing intensity, and repeat cycles through an approved procedure. Use splash goggles, a coat, and chemically compatible gloves; work in a suitable fume hood when handling volatile or hazardous materials. Read the relevant safety data sheets. [6]
- Inspect and prepare. Check for cracks, chips, damaged seals, and a binding valve. Verify correct stopcock assembly and test for leaks with a compatible test liquid. Practice flow control before handling a valuable sample. [3]
- Support, close, and label. Stabilize the lab stand, check the fitted support ring and its stand connection, close the stopcock, and put a collection beaker below the stem. Prepare separate, labeled receiving beakers for both layers.
- Load with room to work. Add the specified liquids using a suitable filling funnel. Remove the filling funnel before fitting the correct stopper. Do not load hot liquids. [4]
- Control both ends during mixing. Hold the stopper securely with one hand and control the body and valve with the other. Gently invert and vent promptly with the outlet pointing into a safe area of the hood, away from people. Position the inverted funnel so the stopcock communicates with the gas headspace before opening it. Close the valve before further mixing. [6]
- Repeat the prescribed mixing and venting. Increase contact only as the procedure permits. Vent frequently. A quiet vent is not proof that later pressure cannot develop.
- Settle upright. Return the funnel to its support and remove the stopper. Allow a defined interface to form. Settling time depends on the mixture. [7]
- Drain under observation. With the stopper removed, collect the lower phase through the valve. Reduce the flow near the interface. If needed, collect an uncertain boundary fraction separately rather than blending it into a clean collection. [8]
- Collect the upper phase separately. Pour it through the mouth into its labeled receiver when the procedure calls for removal. Keep the fractions traceable through any further extraction, wash, drying, or analysis. [8]
Volatile solvents and gas-forming washes can increase pressure. Ordinary separatory funnels are not pressure reactors or vacuum receivers. Do not heat a closed funnel, improvise compressed-air clearing, or add a gas-generating wash without a procedure that addresses the reaction and venting.
7. Why several smaller extractions can outperform one large one
Here is a mathematical teaching example, not a solvent recommendation. Suppose a neutral solute has a constant partition coefficient K = Cextract / Coriginal = 4, the original phase is 300 mL, and 150 mL of fresh extraction solvent is available. Assume equilibrium, immiscible phases of unchanged volume, and no handling losses or chemical reactions.
For one extraction, the fraction left in the original phase is:
One 150 mL extraction: 300 / (300 + 4 × 150) = 1/3 remaining → 66.7% extracted.
Three fresh 50 mL extractions: [300 / (300 + 4 × 50)]³ = 0.216 remaining → 78.4% extracted in total.
The second result uses the same total solvent volume, but restores a favorable concentration difference with each fresh portion. Actual recovery depends on the system; pH-dependent ionization, emulsions, partial miscibility, and transfer losses can change the outcome. More extraction steps also take time. Optimize through the method rather than assuming that more cycles are always worthwhile.
8. Troubleshooting without sacrificing the sample
| Observation | Possible explanation | Practical response |
|---|---|---|
| Cloudy band at the interface | Dispersed droplets or suspended material. | Pause and allow settling; use gentler mixing next time. Any salt addition, solvent adjustment, or centrifugation must be compatible and authorized by the method. |
| Only one visible phase | Miscible liquids, incorrect fraction, or a composition that prevents phase separation. | Check the liquid identities, additions, and retained fractions. Extra shaking cannot make a fully miscible solvent pair separate. |
| Slow or interrupted drainage | Stopper left in place, an obstructed stem, or valve trouble. | Confirm the stopper is removed. Stop if an obstruction remains; never force it clear using gas pressure or a sharp tool. |
| Drips from the valve | Incorrect assembly, poor adjustment, wear, or damage. | Contain the leak and transfer safely. Inspect after emptying; do not tighten aggressively against the glass. |
| Unclear boundary | Dark liquid or an emulsion. | Improve suitable illumination and preserve an uncertain fraction separately. Do not drain blindly into the retained product. |
| Repeated low recovery | Unfavorable distribution, wrong retained layer, incomplete contact, or transfer loss. | Review labels and the complete method. A larger funnel alone does not correct unsuitable solvent chemistry. |
Troubleshooting combines the cited technique references with conservative handling recommendations. There is no universal emulsion-breaking additive.
9. Cleaning, compatibility, and useful boundaries
Clean promptly using a procedure compatible with the residues, seals, and glass. Collect solvent rinses and contaminated liquids in the appropriate waste stream. Disassemble the valve only as directed, inspect the components, and dry before storage. Do not force a seized stopper or stopcock.
Borosilicate glass and PTFE are useful laboratory materials, but neither means “compatible with everything.” Consider all wetted parts, temperature, concentration, and exposure time. Hydrofluoric acid attacks glass; strongly alkaline conditions can also damage it. Confirm the manufacturer’s compatibility guidance for the actual chemicals.
A separatory funnel is also not a precision volumetric measuring instrument, a solids filter, a drying agent, or proof that a collected material is safe for consumption. Phase separation removes bulk liquid; dissolved water and other impurities may remain. Those questions belong to later preparation and testing steps.
10. Questions customers commonly ask
Can it separate alcohol and water?
Ordinary ethanol and water mix into one phase. A separatory funnel cannot simply drain them apart. Special multicomponent systems can behave differently, but require a defined method.
Is a 2 L funnel twice as effective as a 1 L funnel?
No. Capacity determines the space available. Separation performance depends on the liquid system, phase volumes, contact, settling, and handling.
Does a PTFE stopcock guarantee zero leaks?
No. Correct assembly, intact parts, appropriate adjustment, and pre-use checks still matter. Avoid treating material choice as a performance guarantee.
Can I use a dropping funnel instead?
Do not assume interchangeability. A dropping funnel is designed primarily for controlled addition; connections and pressure-equalizing features may differ. Select glassware for the actual operation.
Which VLS option should I choose?
Start with combined liquid volume and required headspace. Then check safe handling, the correct support, valve configuration, and the selected variant’s supplied parts. Compare the listed 1 L and 2 L options and ask VLS to confirm any unlisted dimensions or joint specifications.
Identify the support hardware in the setup photograph
The assembled photograph makes the overall arrangement easier to understand. These separate product images show which part performs each support function. Select dimensions and load suitability before treating individual parts as a matched system.
Plate base and upright: keep the complete load balanced over the base.
The fitted, cushioned ring supports the funnel body during settling and draining.
The boss head joins compatible rods and support hardware to the upright.
A secondary clamp is conditional on documented suitability and permitted glass contact.
Prepare the receivers and cleanup tools
Use separate, labeled collection beakers for retained fractions. A flask cleaning brush set can assist with compatible glassware cleanup after residues are safely addressed; select a brush that reaches the interior without forcing the neck or valve passages. Do not use cleaning tools to force open an obstructed stopcock.
For hand protection, compare the nitrile glove listing with the solvent-specific permeation data required by your method. A generic disposable glove must not be assumed suitable for prolonged hexane exposure.
Explore the Viking Lab Supply Learning Hub for related technique and equipment guides.
Technical references and further reading
The illustrations are original educational schematics. They do not reproduce a manufacturer’s engineering drawing. Product details were checked against the public VLS listing on October 18, 2026; prices and stock are intentionally omitted.
- Viking Lab Supply — Borosilicate Glass Separatory Funnels. Product reference for listed capacities and stopcock material.
- CHEM 231 Lab Technique Primer — The Separatory Funnel. Phase identity, distribution, and washing terminology.
- University of Wisconsin–Madison — Assembling the Stopcock.
- University of Wisconsin–Madison — Pouring Liquids into the Funnel.
- U.S. EPA — Method 3510C: Separatory Funnel Liquid–Liquid Extraction. Environmental analytical sample preparation.
- University of Wisconsin–Madison — Separatory Funnel Safety.
- University of Wisconsin–Madison — Mixing the Liquids.
- University of Wisconsin–Madison — Separating the Two Layers.
- Lisa Nichols — Organic Chemistry Lab Techniques: Step-by-Step Procedures for Extractions. Additional reading on handling and troubleshooting.
- Tomi et al. — Enantioselective GC–MS analysis of volatile components from rosemary essential oils and hydrosols. Primary research; analytical n-hexane extraction example, not a production protocol.
- Lavender hydrosol analysis using UV spectroscopy data and partial least squares regression. Primary research comparing extracts made with pentane, heptane, and diethyl ether.
- CDC/NIOSH — n-Hexane Pocket Guide. Physical properties and occupational hazards.