What Is a Burette?
A burette (or buret) is a piece of laboratory glassware used to dispense precise and variable amounts of a liquid, particularly in a chemical analysis process called titration. It consists of a long, graduated glass tube with a stopcock at the bottom that allows the user to control the flow of the liquid.
Section 2: Key Components of a Burette
The main components of a burette are the graduated tube, a stopcock, and a tip. The glass tube is marked with volume measurements (typically in milliliters) that increase from top to bottom. The stopcock is a valve that can be turned to accurately start, stop, or slow the flow of the liquid, while the narrow tip ensures the liquid is delivered in a controlled stream or drop by drop.
Section 3: A Practical Example of Using a Burette
In a standard acid-base titration, a burette is filled with a solution of known concentration, called the titrant (e.g., sodium hydroxide). This titrant is then slowly added to a flask containing the analyte (e.g., hydrochloric acid) until the reaction reaches its endpoint, often signaled by an indicator's color change. The burette allows the chemist to record the exact volume of titrant used to neutralize the analyte.
Section 4: Why Are Burettes Important?
The importance of a burette lies in its high degree of accuracy and precision for dispensing liquids. Unlike a graduated cylinder meant for approximate measurements, a burette is a key tool for quantitative analysis. Its design allows for volume readings to two decimal places (e.g., 15.25 mL), which is critical for calculating unknown concentrations and ensuring reliable experimental results.