Forward and Backward Pipetting
There are two ways to pipet defined volumes with graduated pipettes, forward and backward. Forward is when the liquid is drawn as high as needed into the pipette and emptied at the destination. Backward is when you fill the pipette to its uppermost graduation and release a measured amount into the destination. The latter is more accurate for viscous mediums, although the loss of substance remaining in the pipette is an obvious disadvantage. The graduation printed onto a pipette corresponds to the intended use, as seen below. Upper: backward (10 at tip) Lower: forward (zero at tip).
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