Pipettes

Pipettes are used to measure and deliver specific volumes of liquid accurately. Depending on the volume required, the size of the pipettes vary but all pipettes work through the same mechanism. A ‘bulb’ at the top of the pipette (usually a glass cylinder with a specified volume marked) is used to create suction and draw the liquid up the pipette, until the desired volume is reached. This is much more accurate than a measuring cylinder as the neck of a pipette is narrower than that of measuring cylinder, so the meniscus (the lower curve in the top of a surface of liquid, where scientists measure volume from) is much easier to read, making the reading more accurate.

Uses

You may have seen pipettes before in your learning. Small, plastic pipettes are often used in experiments such as in ion tests to deliver CO2 into limewater to test for CO3, or to add a reagent dropwise into a solution. Larger 25cm³ pipettes are used in titration experiments to accurately isolate 25cm³ of a reagent before adding a neutralising reagent dropwise via a burette

How to Use

The video below by Nikki Zimmerman on youtube shows how to use a glass pipette (often referred to as a bulb pipette due to the plastic bulb attatched)

Images

Image 1 of volumetric or bulb pipettes by Gmhofmann – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=16962340

Image 2 of a meniscus by PRHaney – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=9472731

Image 3 of pipetting bulbs by Paweena.S – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=60001446

This work is licensed under a Creative Commons Attribution 4.0 International License.