Generally, calibrate glassware to five significant figures; the maximum precision is to attain filling or delivering solutions. The net weight of water needs to be five figures. If the glassware exceeds 10ml, it means weighing 1 mg is all needed.
Volumetric flask calibration
For volumetric flask calibration, first weigh the clean, dry flask and stopper. Then fill distilled water up to the mark, and no droplets on the neck. If any droplet is on the neck or outer surface of the flask, first wipe or clean it with tissue paper. Weigh the filled flask, and record the water’s weight and temperature at 0.1◦C. The rise in weight indicates the weight in the air of the water contained by the flask.
Pipet calibration
For pipet calibration, weigh a dry flask with a rubber or a weighing bottle with a glass stopper or cap, depending on the volume of water to be weighed. Fill the pipet with distilled water and transfer the water into the flask or bottle; use the proper pipetting technique, and stopper the container to avoid evaporation loss. Reweigh to obtain weight in air of water delivered by the pipet.
Buret calibration
The buret calibration procedure is the same as the pipetting procedure; only the volumes will be delivered. The internal bore of the buret is not perfectly cylindrical, so the actual volume shown will vary with plus and minus from the nominal volume marked on the buret as increased volumes are delivered. The volume at 20% full-volume increments by filling the buret each time and then delivering volume into the dry flask. The delivery volume does not have to be exact but close to the nominal volume; you can make fairly fast delivers but wait for about 10 to 20s for film drainage.
Prepare a plot of volume correction versus nominal volume and draw straight lines between each point. Typical volume correction for a 50 ml buret may range to 0.05 ml plus or minus.
