Pipets (or pipettes) are used to transfer reagents from a holding container to a reaction vessel like a test tube or beaker. They may be precisely graduated for one or more volumes or may be completely ungraduated. Due to the narrow width of pipets, graduations are very precise and allow the recording of four significant digits.

Graduated Pipets

Graduated pipets have a full graduated scale to their maximum volume and may be used to measure many different volumes of liquid. As with graduated cylinders, the smallest graduated pipet that will hold the desired measured volume should always be used. This maximizes the precision of the measurement. Measured volumes are recorded to one decimal place beyond that which is indicated by the graduations.

Graduated pipets come in three types:

Type 1 - Reverse Graduated - Partial Delivery: These pipets feature the zero mark at the top of the pipet and include a maximum volume (nominal volume) somewhere near the bottom of the pipet. The pipet is first filled to the zero mark, then allowed to drain to the required volume. The pipet is never drained completely during measurement.

Type 2 - Standard Graduated - Full Delivery: These pipets feature the zero mark at the bottom of the pipet with the nominal volume at the top of the pipet. The pipet is filled until the required volume (up to the nominal volume) is achieved, then is allowed to drain completely into the reaction vessel.

Type 3 - Reverse Graduated - Full Delivery: These pipets are similar to Type 1 Pipets except the nominal value can only be achieved by draining the pipet completely.

Pasteur Pipets

Pasteur pipets (or dropper pipets) are essentially eye droppers used to transfer liquids in a dropwise fashion. They may be plastic or glass, will have a detachable siphon bulb, and are ungraduated. Often volume is not a concern when using dropper pipets, but when they are used quantitatively, the accepted volume equivalence used is 20 drops = 1mL.

The tip of the dropper should always be held high enough above the reaction vessel so that the tip cannot be splashed when the drops fall.
Pipets should never be placed on the lab bench due to the potential for sample contamination and spreading of chemicals.
When using pipets from a dropper bottle, the bottle should always remain in your hand while the pipet is out to prevent pipets from being inserted into the wrong bottle.

Transfer Pipets

Transfer pipets (or Beral pipets) are one-piece plastic pipets used for transferring reagents. They may or may not be graduated but are not considered to be precise or accurate. They may be used, however, to precisely fill graduated cylinders or volumetric flasks to the fill line. Transfer pipets are typically disposable.

Volumetric Pipets

It is also known as bulby pipette or belly pipette. It is commonly used in analytical chemistry in making laboratory solutions from stock and preparing solutions for titration. Its bulb is sizable, and its part is long and thin. They are most effective for quick measurements since they may be calibrated to give a precise set volume of liquid with an accuracy of up to 4 significant digits.