A burette is a long, graduated glass or plastic tube fitted with a stopcock at the bottom, used to dispense precise, variable volumes of liquid—most commonly during titrations. Unlike a pipette, which delivers one fixed volume, burettes let you control exactly how much liquid flows out, drop by drop if needed, while reading the volume dispensed directly off the graduated scale.
The History Behind the Burette
The burette didn't appear overnight—it evolved through a handful of very specific improvements, each solving a problem the last design couldn't.
The earliest version showed up in 1791, when French chemist François Antoine Henri Descroizilles built a device that looked more like a graduated cylinder than a modern burette—no stopcock, just a scale. It got the job started, but it wasn't exactly precise.
In 1824, Joseph Louis Gay-Lussac improved the design by adding a side arm and, in the same paper on standardizing indigo solutions, coined the actual word "burette"—French for a small vase or oil cruet. That's genuinely where the name comes from.
The real leap forward came in 1855, when German chemist Karl Friedrich Mohr redesigned the burette entirely, adding a short length of rubber tubing at the bottom controlled by a pinch clamp of his own design. This let chemists dispense liquid continuously or drop by drop while reading the scale at a glance—and it appeared in Mohr's influential textbook on titration methods, a book that ran through at least 11 editions. Within a few years, earlier designs had essentially vanished from use.
Standardization came much later. ASTM introduced Class A and Class B tolerance specifications for burettes in the early 1960s, and the International Organization for Standardization followed with ISO 385, first published in 1964 and consolidated into its current form, ISO 385:2005.
Parts of a Burette
A standard burette isn't a complicated instrument, but each part earns its place:
- Graduated tube—the long glass (or plastic) body marked with precise volume measurements along its length
- Stopcock—the valve near the bottom that controls whether liquid flows and how fast
- Capillary tip—the narrow, tapered opening at the very bottom, where liquid exits drop by drop
- Burette clamp and stand—holds the burette securely vertical during use, since a wobbling burette makes accurate readings nearly impossible
Types of Burettes
Not every burette is built the same way, and the differences matter more than they might first appear.
Acid Burette
An acid burette uses a glass stopcock at its base and is designed for acidic or oxidizing solutions. It should never be used for alkaline (basic) solutions, because strong alkalis can react with glass over time and cause the stopcock to seize up entirely—a frustrating discovery mid-experiment.
Base (Alkali) Burette
A base burette skips the glass stopcock altogether, using a length of rubber tubing with a small glass bead inside to control flow instead. Squeezing the tubing against the bead lets liquid through; releasing it stops the flow. This design exists specifically because alkaline solutions are hard on glass-to-glass contact points.
Modern PTFE Stopcock Burettes
Today, many burettes use PTFE (Teflon) stopcocks instead of glass or rubber. PTFE doesn't need lubrication, resists chemical attack from both acids and bases, and has largely reduced the practical need for separate "acid" and "base" burette designs in modern labs.
Digital and Automatic Burettes
Digital burettes add electronic volume tracking and dispensing control, cutting down on human reading error and speeding up repetitive titrations—a meaningful upgrade for labs running high volumes of quality-control testing.
Piston and Weight Burettes
Less common but still in use, a piston burette works more like a syringe, using a precision bore and plunger (sometimes motorized) to dispense liquid. A weight burette, meanwhile, measures dispensed liquid by weight rather than volume—useful in specific high-precision applications.
Class A vs. Class B Burettes: Why It Matters
Like most precision glassware, burettes are manufactured to one of two tolerance grades, etched right onto the glass.
Class A burettes carry a tighter, stricter tolerance and are the standard choice for regulated, analytical, or research work where accuracy genuinely affects the result. Class B burettes allow a wider tolerance and suit teaching labs and general-purpose work where absolute precision isn't the priority. The exact permissible error for each class and capacity is spelled out in ISO 385:2005—so if two labs across the world are both using Class A burettes, their tolerance expectations match exactly.
How to Read a Burette Correctly
Reading a burette wrong is one of the most common (and most avoidable) sources of error in a titration, so it's worth getting right.
- Lower your eye until it's level with the liquid surface—never read from above or below at an angle, since that introduces parallax error.
- Locate the meniscus, the curved surface the liquid forms inside the tube.
- Read the measurement at the bottom of that curve, not the top edges.
- A standard macro burette (commonly 50 mL or 25 mL) has a minimum scale division of 0.1 mL, but a careful reader can estimate the next digit, giving a reading precise to about 0.01 mL.
That last decimal place is an estimate, not a guarantee—but it's exactly the kind of careful, repeatable habit that makes titration results trustworthy.
What Are Burettes Used For?
The single biggest use of burettes is titration—slowly adding a solution of known concentration (the titrant) to a sample until a reaction reaches its endpoint. This applies across several specific techniques:
- Acid-base titrations – determining the concentration of an unknown acid or base
- Redox titrations – tracking oxidation-reduction reactions to a measurable endpoint
- Complexometric titrations – measuring metal ion concentrations using a complexing agent
Outside titration specifically, burettes also show up anywhere a lab needs controlled, variable liquid dispensing with a precise, readable volume—quality control testing being a common example.
Choosing the Right Burette for Your Lab
A few practical questions make this decision easier:
What are you dispensing?
Acidic and oxidizing solutions favor a glass or PTFE stopcock; alkaline solutions favor PTFE or a traditional rubber-tube design to avoid stopcock seizing.
How much precision do you actually need?
Regulated or research-grade work calls for Class A; teaching labs and general prep are usually well served by Class B.
Manual or digital?
High-throughput labs often benefit from the speed and reduced reading error of a digital burette, while manual glass burettes remain the standard, budget-friendly workhorse for most titration work.
A reliable supplier's range of burettes—covering both acid and alkali configurations, Class A and B tolerances, and manual or automatic dispensing—makes it easier to match the right instrument to each specific job rather than settling for a one-size-fits-all option.
Conclusion
From Descroizilles' rough 1791 prototype, to Gay-Lussac naming it in 1824 to Mohr's game-changing 1855 redesign, the burette has been refined by generation after generation of chemists chasing the exact same goal: precise, controllable, drop-by-drop liquid dispensing. Two centuries later, that same core idea — a graduated tube with a controllable stopcock — still anchors nearly every titration performed in labs worldwide, whether it's a Class B burette in a school classroom or a digital Class A burette running quality control in a pharmaceutical plant.
Frequently Asked Questions
What is a burette used for?
A burette is primarily used for titrations, dispensing precise, variable volumes of liquid to determine the concentration of an unknown solution.
What is the difference between an acid burette and a base burette?
An acid burette uses a glass stopcock and holds acidic or oxidizing solutions, while a base burette uses a rubber tube with a glass bead instead of a glass stopcock, since alkaline solutions can cause a glass stopcock to seize.
What is the difference between Class A and Class B burettes?
Class A burettes have a tighter manufacturing tolerance and suit regulated or analytical work, while Class B burettes have a wider tolerance and suit teaching or general-purpose use, as defined under ISO 385:2005.
How accurate is a burette reading?
A standard burette can typically be read to about 0.01 mL, since the minimum scale division (often 0.1 mL) allows a careful observer to estimate the final digit.
Who invented the burette?
The earliest version was built by François Antoine Henri Descroizilles in 1791. Joseph Louis Gay-Lussac coined the term "burette" in 1824, and Karl Friedrich Mohr's 1855 redesign became the basis for the modern burette.
