A burette is a common laboratory instrument designed for the accurate dispensing of liquids. This long, graduated glass tube allows scientists to deliver precise, measured volumes of solutions. Its fundamental purpose is to provide controlled release of reagents, a requirement in analytical chemistry and scientific investigations. The design supports careful liquid handling, contributing to reliable experimental outcomes.
Precision Liquid Measurement
The primary function of a burette is to measure and dispense variable, precise volumes of liquid. Scientific experiments, especially in quantitative analysis, demand high accuracy. A burette facilitates this by allowing controlled, often drop-by-drop, addition of a solution, ensuring specific amounts of reagents are delivered. This controlled delivery is important when determining the exact quantity of a substance. The instrument’s design enables users to precisely track the volume dispensed, contributing significantly to the reliability and reproducibility of experimental results.
Operational Principles
A burette achieves its precision through design features and careful operational techniques. Made from borosilicate glass for chemical compatibility, it consists of a long, graduated tube with a stopcock at the bottom and a narrow tip. The graduations allow for reading the dispensed volume, with the zero mark usually at the top. The stopcock, a valve, controls the flow of liquid, enabling users to dispense solution in a continuous stream or one drop at a time.
Before use, eliminate air bubbles from the tip and ensure the burette is clean and conditioned with the solution. To read the volume accurately, view the bottom of the meniscus (the curved surface of the liquid) at eye level to prevent parallax errors. The dispensed volume is calculated by subtracting the final reading from the initial reading.
Common Laboratory Uses
Burettes are widely used in laboratories for applications requiring accurate liquid dispensing. Their most prominent application is in titration, a method of quantitative chemical analysis. In titration, a solution of known concentration, called the titrant, is slowly added from the burette to a solution of unknown concentration until a chemical reaction reaches its endpoint, often indicated by a color change.
Beyond titration, burettes are employed in general chemical analysis, quality control, and industrial applications where precise measurement and dispensing of liquids are necessary. The controlled delivery offered by a burette makes it suitable for reactions where slow, incremental addition of reagents is important for observing a specific chemical change.