Laboratory Funnels Compared: Dropping, Separatory, and Pressure Equalising

Funnels are versatile tools used across laboratories for transferring, separating, and controlling liquid flow. While simple glass funnels are common, specialised types such as dropping funnels, separatory funnels, and pressure equalising funnels play critical roles in chemical synthesis, titrations, and extractions. For Australian schools, universities, and industry labs, choosing the right funnel ensures both accuracy and safety.

Dropping Funnels: Precision in Additions

Dropping funnels are designed to allow controlled addition of liquids during titrations or reactions.

• Available in cylindrical or pear-shaped designs.
• Equipped with glass or PTFE stopcocks for flow control.
• Ideal for titrations, reagent additions, and organic synthesis.
• Made from BORO 3.3 glass for chemical and thermal resistance.

They prevent overshooting in titrations and reduce risks of splashing or sudden chemical addition.

Separatory Funnels: Liquid–Liquid Extraction

Separatory funnels are essential in organic chemistry for separating immiscible liquids.

• Typically pear-shaped or cylindrical with a stopcock at the base.
• Used in solvent extractions and purification steps.
• Available with PTFE stopcocks (low maintenance) or glass stopcocks (heat resistant).
• Transparent BORO 3.3 glass provides visibility for phase separation.

These are widely used in research, pharmaceuticals, and environmental testing.

Pressure Equalising Funnels: Controlled Additions Under Vacuum

Pressure equalising funnels are specialised dropping funnels equipped with a side tube.

• Maintain pressure balance during liquid transfer in closed or vacuum systems.
• Prevent backflow of liquid and minimise risk of breakage.
• Common in organic synthesis and distillation setups.
• Constructed from BORO 3.3 for vacuum and thermal stability.

They are indispensable for precise additions in advanced chemical processes.

Comparison Table: Dropping vs Separatory vs Pressure Equalising Funnels

FAQs

Q1: Why are PTFE stopcocks preferred?
They are chemically resistant and maintenance-free, while glass stopcocks require greasing but withstand higher temperatures.

Q2: Can separatory funnels be used under vacuum?
Standard separatory funnels are not recommended under vacuum; pressure equalising funnels are designed for that purpose.

Q3: Are all funnels autoclave-safe?
Yes, BORO 3.3 funnels are autoclave-safe, but PTFE components may degrade after repeated cycles.

Q4: Which funnel is best for teaching labs?
Dropping funnels are common for titrations, while separatory funnels are essential for teaching organic chemistry extraction techniques.

References

• ISO 4800: Laboratory Glassware — Funnels.
• ASTM E1406: Standard Specification for Laboratory Glass Funnels.
• ISO 3585: Borosilicate Glass 3.3 — Properties and Standards.
• University of Melbourne Organic Chemistry Laboratory Manual.
• NIST Chemistry WebBook, National Institute of Standards and Technology.