22) Lab Essentials : Pipette

Microbiology Lab Essentials :

Glasswares :

22) Pipette : Graduate Pipette

A graduated pipette is a pipette with its volume, in increments, marked along the tube. It is used to accurately measure and transfer a volume of liquid from one container to another. It is made from plastic or glass tubes and has a tapered tip.

Typical volumes are 10, 25, and 50 mL. Alternatively, Mohr pipettes are straight-walled, and graduated for different volumes such as 5 mL in 0.5 mL increments. The single volume pipette is usually more accurate, with an error of ± 0.1 or 0.2 mL.

Graduated pipettes made of glass or plastic are used for accurate measurement of liquid volumes.

Use them for measuring volumes between 1 ml and 10 ml :

For larger volumes, you would use a graduated cylinder, and for smaller volumes.

Graduated pipettes (Mohr pipette) have a scale divided into units of one and of 1/10th of a millilitre. Because of their wide necks it is less accurate than the volumetric pipette. 

They are used when taking volume of solutions in which accuracy does not have to be very high. 

By sucking in (with mouth, propipette or a water pump) the liquid is pulled in a little bit above the mark and the opening of the pipet is closed with a forefingertip.

Outer wall of pipet is wiped and, with a slight forefinger loosening, the liquid is released until it reaches the mark 0(zero). 

A pipette is emptied out by lifting the forefinger off and letting the liquid flow out of the pipette freely.