Plastic Flasks

Erlenmeyer (conical) flasks are for mixing, swirling, titration, and short-term storage. Volumetric flasks with a single calibration mark are for preparing solutions of precise known concentration. Do not use a conical flask as a volumetric flask since it is not calibrated and will give inaccurate concentrations.

For titration, 250 ml conical flasks are the standard size, accommodating 25 ml of titrand with room to swirl. For solution preparation, choose a volumetric flask whose nominal volume matches the solution volume you need. For mixing, choose a flask roughly twice the volume of the liquid to prevent splashing.

PP resists most dilute mineral acids and alkalis. Avoid concentrated nitric acid, aromatic solvents, chlorinated solvents, and ketones such as acetone. For procedures using these chemicals, use borosilicate glass flasks. Always verify compatibility before use, especially with unfamiliar organic reagents.

Conical flasks use rubber or silicone stoppers for temporary sealing. Volumetric flasks have a narrow neck that accepts a ground-glass or PTFE stopper to give an airtight seal during storage. Ensure you have the correct stopper size before preparing your solution.

A conical (Erlenmeyer) flask has a wide base, sloping walls, and a narrow neck. It is used for mixing, swirling, and titration but is not a calibrated volumetric instrument. A volumetric flask has a round base and a very long narrow neck with a single calibration mark used to prepare solutions of exact known concentration. Do not interchange them for quantitative work.

PP Erlenmeyer flasks can withstand moderate heating up to approximately 121 degrees Celsius and may be placed on a low-heat hot plate. They should never be used over a direct flame, Bunsen burner, or high-temperature hot plate, as PP will soften and deform. For heating reactions above 100 degrees Celsius, use borosilicate glass Erlenmeyer flasks.

Class B PP volumetric flasks meet the same accuracy standard as Class B glass volumetric flasks and are suitable for most teaching and routine laboratory standard solution preparation. For primary standard solution preparation used in analytical chemistry research, Class A borosilicate glass volumetric flasks are preferred due to their tighter tolerances and better long-term dimensional stability.

Polypropylene Erlenmeyer and volumetric flasks can be autoclaved at 121 degrees Celsius. This makes them ideal for preparing sterile culture media and buffer solutions in microbiology. Remove any stoppers or closures before autoclaving to prevent pressure build-up inside the flask. Allow to cool before handling and before adding temperature-sensitive reagents.

For a standard school titration using 25 ml of titrand dispensed from a burette, a 250 ml Erlenmeyer flask is the correct choice. It gives ample room to add indicator, accept the titrant from the burette, and swirl vigorously without spilling. The 100 ml flask is suitable for micro-titrations using smaller volumes.