Buretten

Burettes are precision laboratory glassware used to deliver known volumes of liquid during titration experiments. A typical burette is a long, graduated tube with a stopcock at the bottom that regulates flow. The graduations indicate the volume delivered, usually in milliliters, with fine divisions such as 0.02 or 0.05 mL. Burettes are commonly made of borosilicate glass and may have plastic or PTFE stopcocks; typical capacities are 0–50 mL or 0–100 mL.

Operation and reading: the burette is filled with the titrant, ensuring no air bubbles. The initial volume is read at the bottom of the meniscus with the observer’s eye level. As titration proceeds, the stopcock is opened to deliver small portions of liquid; the delivered volume equals the final reading minus the initial reading. Burettes should be kept free of leaks and contamination.

Accuracy and maintenance: high-precision burettes are calibrated under specified conditions; readings are sensitive to parallax, temperature, and liquid viscosity. Before use, the burette is rinsed with the titrant and then drained. After use, it is cleaned and dried, and stored vertically to prevent stress on the glass or clogging of the stopcock.

Variants and applications: there are mechanical and automatic burettes for automated titrations, as well as microburettes for very small volumes. Burettes are standard equipment in chemical analysis, chemistry teaching laboratories, environmental testing, pharmaceuticals, and research where precise measurement of liquid volumes is required.