How to choose a burette in chemistry for accurate titration work

A burette in chemistry is a graduated dispensing instrument used mainly to deliver a controlled volume of liquid during titration. Capacity is only one part of the buying decision. The right burette also has to fit the method, required accuracy, chemical compatibility, operator skill level, cleaning routine, and documentation requirements of the laboratory.

For routine demonstrations, a general-purpose glass burette may be enough. For analytical quality control, a Class A or Class AS burette with traceable calibration documentation is often the better choice. For repetitive titrations, a digital or automatic burette may reduce operator fatigue and improve workflow, but it also brings added maintenance and verification requirements.

This guide focuses on practical selection rather than brand ranking. For more laboratory equipment selection articles, visit our Buying Guides section.

What a burette does in chemistry

A burette, also spelled buret in many U.S. catalogs, is used to dispense liquid in measured amounts. Its most familiar role is titration, where a reagent of known concentration is added gradually to a sample until the reaction reaches an endpoint. The IUPAC Gold Book describes volumetric titration as titration in which the titrant is added by volume, usually from a calibrated burette. In practice, that means the burette is part of the measurement system, not just a container.

The delivered volume is normally calculated from two readings: the initial reading before dispensing and the final reading after dispensing. The difference between them is the volume delivered. Readability, stable flow control, removal of air bubbles, and correct meniscus reading all affect the quality of the titration result.

A burette is most useful when the endpoint is not known in advance. Unlike a volumetric pipette, which transfers a fixed volume, a burette lets the operator add solution quickly at first and then dropwise near the endpoint. This controlled delivery makes it suitable for acid-base titrations, redox titrations, complexometric titrations, precipitation titrations, and other volumetric methods where a small volume difference can change the reported concentration.

Main types of burettes and where they fit

Glass volumetric burettes

Traditional glass burettes remain common because they are simple, transparent, chemically resistant for many aqueous solutions, and easy to inspect. A typical glass burette has a graduated tube and a stopcock at the bottom. Many are made from borosilicate glass, which provides good chemical and thermal resistance for general laboratory use.

Glass burettes are a strong choice for education, routine wet chemistry, and laboratories that need visible liquid level control. They are also easy to check for cleanliness, bubbles, leakage, and tip condition. Their limitations are equally familiar: they can break, they require manual reading, and accuracy depends heavily on technique.

Digital burettes

Digital burettes use a piston or dosing mechanism and show the delivered volume electronically. They are useful when a lab performs many repeated titrations or wants to reduce reading errors caused by parallax and meniscus interpretation. Some digital systems can also improve workflow by giving smoother dispensing and a clearer volume display.

The trade-off is complexity. Digital burettes require compatible reagents, periodic performance checks, battery or power management, seal inspection, and cleaning procedures that suit the titrant. They are not automatically more accurate in every application. Their value depends on calibration status, maintenance, and the requirements of the method.

Automatic and bottle-top burettes

Automatic burettes and bottle-top titration devices are designed for repeated dispensing from a reservoir. They can speed up routine titrations and reduce the need to refill a long glass tube. In production support labs or high-throughput teaching labs, that convenience can be significant.

Buyers should still check reagent exposure, bottle stability, adapter compatibility, dead volume, and cleaning access. If the titrant crystallizes, absorbs carbon dioxide, attacks seals, or needs protection from light, the dosing system must be selected with those conditions in mind.

Buying specifications that affect accuracy

The key specifications are accuracy class, capacity, graduation interval, calibration basis, and documentation. Standards such as ISO 385 and ASTM E287 are commonly associated with laboratory glass graduated burettes. Because standards and procurement rules can differ by region and industry, buyers should confirm the exact standard edition and acceptance criteria required by the lab’s quality system before purchase.

Specification	What to check	Why it matters
Accuracy class	Class A, Class AS, or Class B	Class A and AS products generally have tighter tolerances than Class B products and are preferred for analytical work.
Capacity	10 mL, 25 mL, 50 mL, or other size	The delivered titration volume should fall in a useful part of the burette range, not only at the first few marks.
Graduation interval	Commonly 0.1 mL on many 25 mL and 50 mL burettes	Finer graduations make reading easier, but technique and tolerance still limit usable precision.
Tolerance	Manufacturer’s stated permissible error	For example, many 50 mL Class A or Class AS burettes are specified around ±0.05 mL, while comparable Class B versions may be around ±0.10 mL. Buyers should verify the actual certificate or product data.
Calibration mark	TD or Ex marking	Most burettes are calibrated to deliver a stated volume, so the reading difference represents the dispensed volume.
Certificate	Batch certificate or individual certificate	Regulated or audited labs may need traceable documentation rather than a simple catalog claim.

For many general chemistry labs, a 50 mL burette is versatile because it covers common titration volumes while remaining easy to read. A 25 mL burette may be better when sample sizes are smaller and expected titrant use is lower. A 10 mL burette can be useful for micro-scale or reagent-saving work, but it requires careful handling and may not suit every teaching environment.

A common purchasing mistake is choosing the largest size by default. Oversizing can increase relative reading uncertainty when the delivered volume is small. If a method usually consumes only 2 or 3 mL of titrant, a smaller burette or a revised method design may provide better practical measurement quality.

Materials, stopcocks, and chemical compatibility

The tube material, stopcock material, and tip design determine how well the burette performs with real reagents. Borosilicate glass is widely used for aqueous acid-base titrations and many inorganic solutions. Amber glass may be selected for light-sensitive titrants. Plastic components can reduce breakage risk, but they must be checked for chemical compatibility, leaching risk, and dimensional stability.

Stopcock choice deserves close attention. Glass stopcocks offer good chemical resistance in many applications, but they may require proper lubrication and careful handling. PTFE stopcocks are popular because they provide smooth operation and broad chemical resistance for many laboratory reagents. They can also reduce the maintenance associated with ground-glass keys. However, PTFE is not a universal answer for every chemical system, especially where swelling, permeation, or strong oxidizing conditions are concerns.

The best stopcock gives fine flow control without leakage. During titration, the operator must be able to move from a steady stream to single drops near the endpoint. A stiff, loose, or leaking stopcock can cause overshooting, inconsistent delivery, or loss of confidence in the final result.

Tip design also matters. A clean, well-shaped tip supports consistent drop formation. A chipped or contaminated tip can retain droplets, release titrant unpredictably, or force the operator to touch off drops more often. When comparing models, do not treat the tip as a minor detail; it is the final point where measured liquid becomes delivered liquid. See also: Storage Systems.

Reading and handling practices that protect measurement quality

Even a high-grade burette can produce poor data if it is read or handled incorrectly. Chemistry teaching materials, including university laboratory manuals and Chemistry LibreTexts resources, consistently emphasize reading the meniscus at eye level to reduce parallax error. For clear aqueous solutions in a glass burette, the bottom of the meniscus is usually read. Dark or opaque liquids may require a method-specific reading convention.

Before use, the burette should be clean, rinsed with deionized water, and conditioned with a small portion of the titrant unless the method states otherwise. Conditioning helps prevent residual water from diluting the titrant. The tip must be filled with solution and free of air bubbles before the initial reading is recorded. A trapped bubble in the tip can make the calculated delivered volume larger than the actual amount that entered the flask.

During titration, the operator should add titrant quickly only when far from the endpoint. Near the endpoint, slower addition and steady swirling improve control. If a hanging drop remains on the tip, the method should define whether and how it is rinsed into the flask. Consistency matters because small differences near the endpoint can affect the final concentration calculation.

After use, the burette should be emptied, rinsed, and stored according to the reagent and lab procedure. Alkaline solutions can attack glass over time, and some titrants can crystallize or clog the stopcock and tip. Long-term storage with reagent inside a burette is usually poor practice unless the method and equipment are designed for it.

A practical selection checklist for common lab needs

For a school or introductory teaching lab, durability, readability, and cost often matter as much as top-tier accuracy. A 25 mL or 50 mL general-purpose glass burette with clear graduations and a reliable PTFE stopcock is often practical. If students are learning manual titration technique, transparent glass also helps instructors demonstrate bubbles, meniscus position, and endpoint control.

For quality control and analytical laboratories, documentation becomes more important. Look for Class A or Class AS burettes, serial identification where required, and certificates that match the laboratory’s traceability policy. Confirm whether the method, standard operating procedure, or audit program requires a specific standard, calibration interval, or acceptance tolerance.

For corrosive, staining, or light-sensitive titrants, prioritize compatibility. Amber glass may help with light-sensitive reagents, while PTFE stopcocks may improve handling for many common titrants. For highly aggressive reagents, check the chemical resistance of every wetted part, including tubing, seals, adapters, and the tip.

For repetitive titration work, consider whether a digital or automatic burette reduces total labor and variability. The purchase price may be higher, but the workflow gain can be worthwhile if the lab performs the same method many times per day. The decision should include consumables, replacement seals, cleaning time, verification procedures, and operator training.

• Choose capacity based on expected titrant consumption, not habit.
• Use Class A or Class AS when analytical accuracy and documentation matter.
• Check whether the burette is calibrated to deliver and at what reference temperature.
• Match tube, stopcock, seals, and tubing to the reagent.
• Inspect readability, graduation contrast, and scale orientation before purchase.
• Plan cleaning, storage, and periodic verification before the burette enters service.

Common mistakes when buying a burette

The first mistake is focusing only on price. A very low-cost burette may be adequate for non-critical demonstrations, but it can become expensive if poor stopcock control, unclear graduations, or weak documentation causes repeated titrations. The second mistake is assuming that all Class A markings are equal without checking the certificate, standard reference, and supplier documentation.

The third mistake is ignoring the operating environment. In a busy teaching lab, breakage resistance and easy replacement may be important. In an audited analytical lab, traceability and calibration records may matter more. In a production support lab, speed and repeatability may justify automated dispensing. The same burette is not ideal for every setting.

The fourth mistake is forgetting maintenance. A burette is a measuring instrument, not just glassware. Stopcocks wear, tips chip, graduations fade, residues build up, and calibration status can expire. A sound buying decision includes not only the first purchase but also the procedures that keep the instrument reliable.

Frequently asked questions

What is a burette used for in chemistry?

A burette is used to deliver a measured volume of liquid, most often during titration. It allows the operator to add titrant gradually and calculate the delivered volume from the difference between the initial and final readings.

Is a Class A burette always necessary?

No. Class A or Class AS burettes are preferred when accuracy, traceability, or audit requirements are important. For basic demonstrations or rough instructional work, a general-purpose or Class B burette may be sufficient if the limitations are understood.

What size burette should a lab buy?

The right size depends on expected titrant volume. A 50 mL burette is versatile for many routine titrations, while 25 mL or 10 mL models may be better for smaller samples or lower reagent consumption. The expected endpoint volume should fall comfortably within the readable working range.

Why must the meniscus be read at eye level?

Reading at eye level reduces parallax error. If the operator reads from above or below the graduation mark, the apparent volume can shift. For clear solutions, the bottom of the meniscus is commonly used unless the method specifies a different convention.

How often should a burette be calibrated or verified?

The interval depends on the laboratory’s quality system, the method’s criticality, frequency of use, and risk of damage or contamination. Regulated labs should follow their standard operating procedures and applicable standards rather than relying only on the original purchase certificate.