- Introduction
In Bio121, for your pleasure and edification, we have developed several computer simulations/previews of the laboratory exercises. To view these exercises you will need the (free) Flash plug-in. If you do not see anything in the space below, you can download it here. You may have to close and restart your browser to complete the installation, its easy - just follow the instructions.

Pipettes - A pipette (also called a pipet or a pipettor) is a laboratory instrument used to transport a measured volume of liquid. There are many types of pipets; three are shown on the left.

A Pipet can have two types of markings on it: TC ot TD. TC means "to contain". A pipet with this marking has been calibrated to contain a specified volume of liquid. A pipet marked TD (the more common type of pipet) has been calibrated "to deliver" a specified volume of liquid.

When filling a pipet, the tapered end is held beneath the surface of the liquid at all times. The liquid is drawn into the pipet by suction until the level is equal to or greater than the volume of liquid to be delivered. Pipettes are designed to be used with a hand pump or bulb, of which there are many varieties. Never use your mouth with a pipet!

We typically have 1, 5, 10, and 25 ml pipettes available for use in the lab. The pipettes are clearly labelled as to the volume markings and subdivisions. It is imperative that you read the label on the pipette body before using it to know precisely how to read it.

Click the image for a larger view (new window). Examine the necks of the pipets for their markings. The arrows indicate the starting and finishing points for delivering 10 mL from each pipet.

When loading the pipette, the volume is read at the bottom of the meniscus that forms on top of the column of liquid

Volumetric pipets are designed to transfer a fixed amount of liquid when filled to the mark (e.g. 10 mL and only 10 mL). There is generally only one "fill-line" on a volumetric pipet. Other pipets are graduated, so they can deliver any volume of liquid up to the capacity of the pipet.

Mohr pipets are graduated but the graduations stop at a baseline before the pipet begins to narrow (see arrow on left). To accurately transfer fluid with this type of pipet, the meniscus must be precisely on a calibration mark both at the beginning and at the end of a transfer.

Serological pipets are the type we will use most often in Bio 121. Serological pipets have no base mark (the graduations continue onto the tip) and are graduated to deliver. that means you let all the (measured) liquid in the pipet exit.

Questions: Answer the questions below, then submit them along with your name and section.

1. Which of the below would you use to measure 50 ml of liquid?

10 ml pipet
300 ml Beaker
250 ml Erlenmyer Flask
100 ml Graduated Cylinder

2. The glassware used to titrate solutions is called?

A Bonnet
A Pipet
A Cylinder
A Buret

3. When measuring liquid in a pipet, the volume is determined by looking at...?

The bottom of the meniscus
The top of the meniscus
The middle of the meniscus
What the heck is a meniscus?

4. What does a Spectronic 20 measure?

5. Which type of Pipet will you most likely use in Bio 121?

Volumetric
Mohr
Serological

*Name: (*teaching moment) When submitting electronic forms, especially those for credit, be sure to use your actual first and last name; not just your first name, not your nickname. The name you submit should match that on your registration, therefore the gradebook. Thanks.
Section:

Submit your answers to obtain a printable receipt.