The precision of a burette makes careful measurement with a burette very important to avoid systematic error. When reading a burette, the viewer's eyes must be at the level of the graduation to avoid parallax error. Even the thickness of the lines printed on the burette matters; the bottom of the meniscus of the liquid should be touching the top of the line you wish to measure from. A common rule of thumb is to add 0.02 mL if the bottom of the meniscus is touching the bottom of the line[citation needed]. Due to the precision of the burette, even a single drop of liquid hanging from the bottom of a burette should be transferred to the receiving flask, usually by touching the drop to the side of the receiving flask. Through careful control of the stopcock and rinsing, even partial drops of liquid can be added to the receiving flask.
