9.8 : 玻璃器皿校准

Accurate volume measurements are crucial for solution-based analyses. Standard volumetric equipment includes flasks, pipettes, and burettes.

Volumetric flasks are used to prepare and dilute solutions for a specific volume. They are marked TC, which stands for "to contain."

They are calibrated to contain an accurate volume at specified temperatures, where the minimum coefficient of glass expansion allows a nearly constant volume despite minor changes.

Pipettes labeled TD deliver a specific volume at a given temperature. They are calibrated to account for film drainage on glass walls, which varies with delivery time.

Volumetric pipettes with proper calibration deliver a single volume accurately up to four or five significant figures. Measuring pipettes deliver different volumes with lower accuracy of up to three significant figures.

A burette is a calibrated tube for holding the titrant that can be dispensed accurately via the manual valve system to control the titrant flow.