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Volumetric Flask
Class B Calibration Standards: Individually calibrated "To Contain" (TC) at 20°C with a permanent, high-contrast molded graduation ring to ensure precise meniscus alignment and volumetric accuracy for quantitative analysis.
Leak-Proof Tapered Seal: Equipped with a precision-ground polypropylene stopper that provides an airtight, chemically inert seal, preventing evaporation and contamination during aggressive reagent mixing or long-term solution storage.
$2.93
Quick Answer: A volumetric flask is a bulb-shaped, flat-based flask with a long narrow neck bearing a single calibration mark, used to make up a solution to one exact volume. It is the standard vessel for preparing standard solutions and accurate dilutions in titration and instrumental analysis.
Making Up to the Mark
The flask is calibrated to contain its stated volume when filled so that the bottom of the meniscus sits on the mark, at the reference temperature printed on it, usually 20 °C. To make a standard solution, a weighed solid is dissolved in a little water in a beaker, the solution and all rinsings are transferred through a funnel, and water is added until the level is just below the mark. The last drops go in from a dropper, and the stoppered flask is inverted repeatedly until the solution is uniform.
The listing is titled simply Volumetric Flask and does not state the material, capacity, accuracy class or stopper type. These flasks are made in borosilicate glass, in classes of accuracy, and in plastics such as polypropylene or polymethylpentene. Glass gives the sharpest calibration and the widest solvent resistance; plastic is unbreakable and is preferred for alkaline solutions that slowly attack glass, and for trace-metal work where glass could release ions. Confirm which type and capacity is supplied.
If glass is specifically required, LabEquip also lists a glass volumetric flask. Pouring into the narrow neck is easiest with a long stem plastic funnel, rinsed into the flask afterwards.
Specifications
| Item | Flask with long neck and single calibration mark |
| Calibration | To contain the stated volume at the reference temperature marked on the flask |
| Use | Preparing standard solutions and exact dilutions |
| Closure | Stopper, glass or plastic according to type |
| Material, capacity and accuracy class | Confirm at enquiry |
Care & Handling
- Never heat the flask or fill it with hot solution; dissolve solids in a beaker and let the solution cool first.
- Read the meniscus at eye level with the flask standing on a level surface.
- Keep each stopper with its own flask, and rinse rather than scrub the inside of glass flasks.
- Do not leave alkaline solutions standing in glass flasks, which can fuse the stopper and etch the calibrated neck.
Applications
- Preparing standard solutions of sodium carbonate or potassium hydrogen phthalate for acid-base titrations
- Making calibration standards for colorimetry, spectrophotometry and flame photometry
- Accurate dilution of stock solutions, with the aliquot delivered by pipette
- Preparing reagents to a set concentration in pharmacy and quality control labs
Why Choose LabEquip
Schools, colleges and analytical laboratories need a volumetric flask for every standard solution they prepare, often in several capacities. LabEquip supplies them within its chemistry lab equipment; specify material, capacity and class through the contact page.
Frequently Asked Questions
Why can’t the flask be heated?
Heating expands the glass or plastic and can change its volume permanently, spoiling the calibration. Dissolve and cool solids in a beaker first, then transfer the solution.
How do I read the mark correctly?
Stand the flask on a level bench with the mark at eye level. For colourless solutions, the bottom of the curved meniscus should just touch the line; a white card with a dark band held behind the neck makes the meniscus easier to see.
What does to contain mean on a flask?
The flask holds exactly the stated volume when filled to the mark, but it is not designed to deliver that volume when poured out, because some liquid stays on the walls. Pipettes and burettes are marked to deliver instead.
Glass or plastic: which should I choose?
Glass gives the most accurate calibration and resists solvents. Plastic flasks are unbreakable and suit alkaline solutions and trace-metal analysis, where glass can react or release ions. Many labs keep both for different jobs.
Why must the solution be mixed after reaching the mark?
Water added last forms a less concentrated layer at the top of the neck. Stoppering the flask and inverting it many times, with the stopper held in place, mixes the solution evenly so every portion has the same concentration.
Can I store solutions in the flask?
These flasks are meant for preparation, not storage. Transfer the solution to a labelled reagent bottle so the flask is free for the next preparation and its neck and stopper stay clean.
Last Updated: September 2026
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