Burettes are used for precisely dispensing liquids in laboratory experiments and are available in manual and digital versions. Manual burettes (burets) are tall graduated tubes, with a tap or stopcock at the bottom. ASTM details two specifications for manual glass burettes: Class A (precision grade) and Class B (general purpose grade). Manufacturers sometimes use these classifications for plastic burettes. Digital or bottle top burettes are attached to containers and use microprocessors to measure the liquid that is disbursed and digital displays to provide readout.
Specifications and Features
Volume and materials of construction are important to consider when selecting burettes. In volume, manual burettes can range from 5 to 4,000 cc. In terms of materials, manual burette tubes are usually made from glass or plastic. Stopcocks are generally made from Teflon (PTFE). The nature of whatever liquid is being measured should be considered carefully when choosing a material.
Manual burettes- are marked by gradations appropriate to the volume of the labware-to aid measurement. Stopcocks can feature one or two dispenser tubes, a push-button permitting drop-by-drop delivery, and a small screw clamp that presets drop speed.
Self-zeroing, auto-fill, or automatic kits consist of a plastic bottle and/or rubber bulb that allows for more precise filling or safe handling of hazardous solutions.
Digital burettes can be powered manually (by hand cranking/spinning) or electronically (by batteries or solar panels). They can also feature LCD screens, light protection, recirculation systems and computer interfaces for data logging.