In a laboratory setting, liquid volume is precisely measured using specialized glassware. Liquid volume is usually measured using either a graduated cylinder or a buret. These tools are essential for accurate experiments and procedures.
Primary Tools for Measuring Liquid Volume
Two of the most common and reliable instruments used for measuring liquid volume in a lab are the graduated cylinder and the buret.
Graduated Cylinder
As the name implies, a graduated cylinder is a cylindrical glass or plastic tube sealed at one end, with a calibrated scale etched (or marked) on the outside wall. Graduated cylinders come in various sizes and are used for measuring approximate volumes of liquids. While convenient, they are generally less precise than burets.
- Use Cases: Preparing solutions where exact volume isn't critical, measuring out reagents for reactions.
- Accuracy: Moderate. Readings are typically taken at the bottom of the liquid's meniscus (for clear liquids).
- Sizes: Available from a few milliliters up to several liters.
Buret
A buret (or burette) is a long, graduated glass tube with a stopcock at the bottom. It is primarily used for dispensing variable, measured amounts of liquid, especially in titrations where precise volume delivery is required.
- Use Cases: Titration, precisely dispensing specific volumes.
- Accuracy: High. Burets are designed for precise delivery and are often calibrated to a higher standard than graduated cylinders.
- Reading: Volume is read from the top of the scale downwards, indicating the amount of liquid delivered.
Other Measuring Tools
While the graduated cylinder and buret are fundamental, other tools are also used depending on the required accuracy and volume:
- Volumetric Flasks: Used to prepare solutions of precise concentration. They have a single calibration mark for one specific volume.
- Pipettes: Used to transfer precise volumes of liquid. Types include:
- Volumetric Pipettes: Transfer a single, fixed volume very accurately.
- Graduated Pipettes: Transfer variable volumes, but less accurately than volumetric pipettes.
- Micropipettes: Used for very small volumes (microliters).
Choosing the correct tool depends entirely on the needs of the experiment – whether you need to contain a specific volume, measure an approximate volume, or deliver a precise volume.
