Burettes

Burettes are glass tubes of a constant bore with a graduated scale etched on it and a stopcock at the bottom. The barrel of the stopcock may be glass or plastic. There are burettes with the stopcock at the top but they are used exclusively for gases. These devices are used in analytical chemistry for dispensing variable measured amounts of a chemical solution. They are not to be confused with pipettes because the quantity is variable and not fixed. A funnel is used to fill them to the top without spillage or wastage and they must be checked for air bubbles. The volumetric burette measures volumes of liquid whilst the weight burette measures weights of liquids. The piston burette is similar to a syringe but it has a precision bore and plunger. It may be manually-operated or motorised. The digital type is also like a syringe but the barrel and plunger are both glass. With liquids that corrode glass, a resistant plastic material is used. Motor digital burettes are controlled by computer. Burettes are essential pieces of equipment of any laboratory, whether it is research, industrial or educational. Burettes are used for acid-based reactions in aqueous solutions and in titration.