🔍 Definition
A volumetric flask is a flat-bottomed, pear-shaped flask with a long neck and a single graduation mark etched on the neck to indicate a precise volume (e.g., 100 mL, 250 mL, 1 L). When made of borosilicate glass, it becomes resistant to heat and chemicals.
🔬 Features of a Borosilicate Volumetric Flask
| Feature | Description |
|---|---|
| Material | Made from borosilicate glass (e.g., Pyrex, Duran) known for thermal shock resistance and chemical durability. |
| Graduation Mark | A single, narrow calibration line on the neck that shows the exact volume when liquid reaches that line. |
| Stopper/Cap | Often comes with a ground glass or plastic stopper to prevent evaporation or contamination. |
| Shape | Bulbous bottom with a long, narrow neck for precision. The shape helps in accurate reading of the meniscus. |
| Accuracy Class | Available in Class A (high precision) and Class B (general use) according to ISO or ASTM standards. |
| Thermal Resistance | Can withstand heating and autoclaving without breaking or warping. |
| Volume Ranges | Available in volumes like 25 mL, 50 mL, 100 mL, 250 mL, 500 mL, 1000 mL, etc. |
| Uses | Mainly for preparing accurate standard solutions, diluting samples, and measuring exact volumes. |
✅ Advantages of Borosilicate Glass
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Resistant to thermal stress (can handle heating and cooling)
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Non-reactive with most chemicals
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Durable and long-lasting
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Clear visibility for reading meniscus and contents
🧪 Typical Use in Lab
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Add solute to the flask.
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Add solvent partway and swirl to dissolve.
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Fill up to the graduation mark.
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Stopper and mix thoroughly by inversion.
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