Under a constant temperature and atmospheric pressure, the density of distilled water is constant. The
volume of water can be determined by weighting dispensed water. The calibration of pipette is carried out
by gravimetric method. When determining the volume of water, the accuracy of measurements is effected
by ambient temperature, atmospheric pressure and relative humidity. These factors are usually combined
to give the Z factor, used in calculation of volume of water. Then the calculated volume of water is
compared with the theoretical volume to determine the accuracy and precision of the pipette.