Laboratory Glass Flasks

Select an Erlenmeyer flask for mixing, titration, culture work, and bench use. Use a round-bottom flask when heating on a mantle or running distillation or reflux reactions. Choose a volumetric flask when you need to prepare a solution at an accurate concentration. Opt for a side-arm Buchner flask when vacuum filtration is required.

Fill Erlenmeyer and round-bottom flasks to no more than 50 to 70 percent of their rated capacity during reactions or heating. For volumetric flasks, select the size that matches the exact solution volume you need to prepare. Common sizes range from 50 ml through to 2000 ml.

Round-bottom flasks used in distillation and reflux setups must share the same standard-taper joint size as your condenser and other glassware. The most common sizes are 14/23, 19/26, and 24/29. Confirm all components use the same joint size before purchasing.

Erlenmeyer flasks can be sealed with rubber bungs, glass stoppers, or PTFE-lined screw caps. For halogenated solvents or strong acids, use glass or PTFE closures. Volumetric flasks come with a ground-glass or PTFE stopper matched to that specific flask.

A conical or Erlenmeyer flask has rough graduations and sloping sides you can swirl without spilling, which is why you titrate into one. A volumetric flask is calibrated to a single exact volume marked by one ring on the neck, and is used to make up standard solutions.

Making up a solution to an exact known volume. Dissolve the solid in a little solvent first, transfer it in, then add solvent drop by drop until the bottom of the meniscus sits on the calibration ring. Stopper it and invert to mix.

Erlenmeyer flasks have a flat base and conical body ideal for swirling liquids during mixing and titration. Round-bottom flasks have a spherical base designed to sit in a heating mantle and distribute heat evenly. Use Erlenmeyer for general bench work and round-bottom whenever you need to heat uniformly or connect to distillation assemblies.

Flat-bottomed Erlenmeyer flasks can be placed directly on a ceramic-topped hotplate. Round-bottom flasks should always be used with a heating mantle as their curved base does not make reliable contact with a flat surface. Always pre-warm glass gradually from room temperature to prevent thermal shock.

Yes, borosilicate Erlenmeyer flasks can be autoclaved at 121 degrees C for 15 to 20 minutes for sterilising liquid media. Loosen stoppers before autoclaving to vent steam. Volumetric flasks should not be autoclaved as the heat cycle can alter the calibration volume.

Rinse the flask immediately after use with the appropriate solvent. For stubborn residues, soak in laboratory detergent or dilute acid wash, then rinse with deionised water and air-dry inverted. Avoid abrasive brushes inside volumetric flasks as scratches affect the calibration mark accuracy.