Conical Flask, Plastic

Quick Answer: A plastic conical flask is an Erlenmeyer-shaped flask moulded from plastic, with a flat base, sloping sides and a narrow neck. It is used for mixing, swirling and holding solutions where a glass flask could break, but it is not meant for flame heating.

Choosing a Plastic Conical Flask Over Glass

The shape is the same as the glass Erlenmeyer: a wide base for stability and a narrowing body that keeps liquid inside when it is swirled. What changes is the material. A plastic flask survives a drop onto the floor, weighs less when full, and is a sensible choice for younger classes, field work and any practical where broken glass would be the bigger hazard.

The title does not state the resin. Polypropylene flasks are translucent and generally autoclavable at 121 °C, which suits media preparation and culture work. Polymethylpentene (TPX) flasks come close to glass in clarity and are also generally autoclavable. Polycarbonate is clear but is attacked by alkalis. The choice matters most for titration, where a cloudy wall makes a faint end point harder to see.

For boiling, refluxing or heating on a tripod and gauze, the glass Erlenmeyer flask remains the correct choice. Plastic flasks belong to room-temperature and moderate-temperature work, and to the storage of aqueous solutions.

Specifications

Care & Handling

• Mix by swirling from the wrist while holding the neck; plastic walls flex slightly if the body is gripped hard.
• Avoid scouring pads and abrasive powders, which scratch plastic and make it cloudy; use a soft brush and mild detergent.
• Before autoclaving, confirm the resin and leave any closure loose.
• Wipe off spills of acetone or chloroform promptly, and keep solvent use to liquids the resin is known to resist.

Where Plastic Conical Flasks Are Used

• Class practicals with younger students, where dropped glassware is a real risk
• Preparing and storing aqueous solutions, such as dilute salt or sugar solutions, for later lessons
• Growing yeast or microbial cultures in an autoclavable flask plugged with cotton wool
• Field sampling of pond or stream water, where glass is awkward to carry

Why Choose LabEquip

Schools and training labs that want fewer breakages at student benches often add plastic flasks alongside their glass stock. LabEquip lists this flask in its chemistry lab equipment range; send the capacity and resin you need through the contact page.

Frequently Asked Questions

Can a plastic conical flask be used for titration?

Yes, if the wall is clear enough to judge the colour change. Clear resins such as TPX show end points well, while translucent polypropylene makes faint changes, like the pale pink of phenolphthalein, harder to see against a white tile.

Can I heat a plastic flask on a hot plate?

Not over a flame or on a hot plate. Warm liquids are acceptable within the resin’s temperature limit, and polypropylene or TPX flasks can generally be autoclaved, but direct heating can soften or distort the flask.

Is the flask autoclavable?

It depends on the resin. Polypropylene and polymethylpentene are generally autoclavable at 121 °C, while polystyrene and polyethylene are not. Check the resin marking on the flask before sterilising.

Which chemicals attack plastic flasks?

Strong oxidising acids and many organic solvents, such as chlorinated hydrocarbons, aromatic solvents and, for some resins, acetone, can soften or craze plastics. Dilute acids, alkalis and salt solutions are generally handled well by polypropylene.

Why choose a conical shape rather than a plastic beaker?

The narrowing body stops liquid being thrown out during swirling and slows evaporation, and the neck accepts a stopper or cotton-wool plug. A beaker is easier to pour from but loses liquid when shaken.

Does a plastic flask scratch more easily than glass?

Yes. Plastic is softer, so abrasive cleaning and hard brushes leave marks that trap residues and reduce clarity. Clean with warm water, mild detergent and a soft brush, and replace flasks that have turned cloudy.

Last Updated: September 2026