# 2.2.2 Where an accurate volume is required

For more accurate work, volumetric glassware is used, these include pipettes, burettes and volumetric flasks. A pipette is shown in Figure 6.

Figure 6 A volumetric pipette

Volumetric glassware is calibrated with graduation lines; there may be a scale, or just one line indicating a specific volume. Either way, the key point is measurements must always be read from the lowest point of the meniscus (the concave curvature on top of an aqueous solution), and shown in Figure 7.

Figure 7 Reading the level of a meniscus

- What is the volume of liquid shown in Figure 7?

- 20.30ml

So having had a glimpse inside the laboratory, in the next section you will return to the problem posed at the start of this session, how do chemists quantify amounts of atoms and molecules?

OpenLearn - Discovering chemistry
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