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A volumetric pipette or bulb pipette allows extremely accurate measurement (to four significant figures) a volume of solution. These pipettes have a large bulb with a long narrow portion above with a single graduation mark as it is calibrated for a single volume (like a volumetric flask). Typical volumes are 1, 2, 5, 10, 20, 25, 50 and 100 mL. Volumetric pipettes are commonly used in analytical chemistry to make laboratory solutions from a base stock as well as to prepare solutions for titration.
ASTM standard E969 defines the standard tolerance for volumetric transfer pipettes. The tolerance depends on the size: a 0.5-mL pipette has a tolerance of ±0.006 mL, while a 50-mL pipette has a tolerance of ±0.05 mL. (These are for Class A pipettes; Class B pipettes are given a tolerance of twice that for the corresponding Class A.)
A specialized example of a volumetric pipette is the microfluid pipette (capable of dispensing as little as 10µL) designed with a circulating liquid tip that generates a self-confining volume in front of its outlet channels.
- Helpful Hints on the Use of a Volumetric Pipet by Oliver Seely
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