Calibration of burette
Burettes are calibrated to deliver specified volumes. Burette is marked to indicate
the temperature at which the calibration strictly applied. Burettes have the great precision
of volume measurement.
A burette consists on of a calibrated tube to hold titrant plus a valve arrangement by
which the flow of titrant is controlled. The pinchcock valve consists of a close-fitting glass
beat inside a short length of rubber tubing that connect the burette and its tip; only when the
tubing is deformed does liquid flow past the beat.
A meniscus is the curved surface of a liquid at its interface with the atmosphere. It is
common practice to use the bottom of meniscus as the point of reference in calibrating and
using volumetric equipment. In reading volumes, the eye must be at the level of the liquid
surface to avoid an error due to parallax.
Volumetric glass ware is calibrated by measuring the mass of a liquid (usually
distilled water) of known density and temperature that is delivered by (or contained in) the
volumetric ware.
1. Before calibration check the temperature in laboratory. On analytical balance weight a
dry beaker or weighing bottle.
2. Add 10-15 ml of water to burette and allow the liquid to drain through the tip. Free the
tip of air bubbles by strong stream (jet) of water and permitting small quantities of water
to pass. Finally, lower the level of the liquid just to of somewhat below the zero mark.
Allow for drainage and then lower the water to bring the bottom of the meniscus to the
0,00-ml mark.
3. Slowly transfer 5 ml of water to the beaker. Touch the tip to the wall of the beaker.
Weight the beaker with water.
4. Add more 5 ml of water to beaker (to mark 10-ml on burette). Repeat weighting.
5. Test the burette at 5 ml intervals over its entire volume.
6. Prepare a plot of the correction to be applied as a function of volume delivered. The
correction associated with any interval can be determined from this plot.
Calibration burette data:
Burette
Beaker mass, g
Water mass, g
Volume delivered
Deviation of
water, ml
volume, ml
mark
0
5
10
15
20
25
0,00
0,00
0,00