bureta

A bureta, or burette, is a laboratory instrument used to dispense precise volumes of liquid, primarily in titration experiments. It consists of a long, graduated tube with a stopcock or valve at the bottom end, through which the liquid is released in controlled drops. The tube is usually made of borosilicate glass and marked with fine milliliter graduations, typically holding 50 or 100 mL.

The bureta is filled with the titrant above the zero mark, ensuring there are no air bubbles in the line. The initial measurement is taken at the bottom of the meniscus, viewed at eye level. During titration, small portions of titrant are released by turning the stopcock, and the delivered volume equals the difference between the final and initial readings. Readings should be taken from the bottom of the meniscus to minimize parallax error.

Accuracy and precision depend on good technique and instrument condition. Typical uncertainty for a well-maintained bureta is around ±0.01 to ±0.02 mL per measurement. Common sources of error include parallax, air bubbles, incorrect filling, an improperly sealed stopcock, and temperature fluctuations that affect liquid volume. Regular calibration with standard solutions helps maintain reliability.

Maintenance and variants: Buretas require thorough cleaning, rinsing with the titrant solution, and lubrication of the stopcock as needed. They come in glass and plastic forms, and microburettes exist for very small volumes. While automated titration systems exist, traditional burettes remain a standard tool in many analytical laboratories due to their simplicity and precision. Applications include acid–base, redox, and complexometric titrations.