Burette Guide: Types, Uses, and How to Get Accurate Results

A burette delivers a variable volume of liquid with drop-by-drop control via a stopcock. It is the only common lab instrument designed for titration — finding a chemical endpoint by adding titrant until a reaction completes. The key accuracy factors are tolerance class (A or B per ISO 385), meniscus reading technique, and using the burette in the top half of its range where relative error is lowest.

Pick by the job, not by habit

  • Acid-base or redox titration, aqueous
    Glass burette with PTFE stopcock
    Standard for most titrations; chemically resistant; no grease needed
  • High-throughput titration, many samples per day
    Automatic (self-zeroing) burette
    Auto-refill and zero saves time; sealed reservoir protects titrant
  • Regulated QC, parallax error unacceptable
    Digital (piston) burette
    Electronic readout eliminates meniscus reading error entirely
  • Gas collection or evolved-gas measurement
    Gas burette
    Measures gas volume by liquid displacement — not for liquid titration
  • Small volumes < 5 mL needed accurately
    Volumetric pipette or smaller burette
    Relative error rises fast on small burette deliveries; pipette is better
  • Titrant sensitive to CO₂ or moisture (NaOH, KMnO₄)
    Automatic burette with sealed reservoir
    Open burette exposes titrant to air; sealed system preserves concentration

Burette vs pipette, side by side

  • Reading
    Manual meniscus read at graduation marks
    Electronic display; no meniscus reading
  • Error source
    Parallax; operator technique
    Piston wear; electronic calibration drift
  • Throughput
    One fill per titration run
    Continuous from reservoir; auto-zero
  • Chemical range
    Broad; glass + PTFE resists most reagents
    Depends on piston seal material
  • ISO tolerance
    ISO 385 Class A: ±0.05 mL (50 mL)
    Manufacturer spec; typically tighter
  • Cost
    Low; simple glassware
    Higher; motorised or electronic components

Types of burette and when to use each

Glass burette with PTFE stopcock — the standard for acid-base and redox titrations. PTFE plug is chemically resistant and does not require grease. Use for most aqueous titrations in teaching and QC labs.

Automatic (self-zeroing) burette — refills and zeros automatically from a reservoir bottle. Reduces repetitive filling time in high-throughput titration work. The reservoir is sealed to protect titrant from CO₂ and moisture.

Digital burette (piston burette) — motorised or manual piston dispenses into a tip, reads volume electronically. Eliminates meniscus reading error entirely. Used in regulated QC environments where parallax error is unacceptable.

Gas burette — measures gas volumes by liquid displacement. Used in gas collection and evolved-gas experiments, not liquid titration.

The three accuracy rules every burette user needs

  1. Rinse with titrant before filling. Residual water on the glass walls dilutes the first portion of titrant. Rinse two or three times with small volumes of titrant, drain fully, then fill.
  2. Read the meniscus at eye level. The eye must be exactly level with the bottom of the meniscus. Reading from above gives a falsely low reading; from below, falsely high — a systematic offset every titration.
  3. Use the top half of the scale. A Class A 50 mL burette has ±0.05 mL absolute tolerance. At 40 mL delivery that is 0.1 % relative error. At 4 mL delivery it is 1.25 %. Deliver large volumes when accuracy matters; use a smaller burette or a volumetric pipette for small precise volumes.

Standards

  • ISO 385:2005
    Burettes — Class A and Class B tolerance limits, graduation, and test methods
  • ISO 4787:2021
    Laboratory glassware — volumetric instruments; methods for testing and use
  • ISO 8655-6
    Gravimetric test method — applicable as reference verification for digital burettes

Frequently asked questions

  • What is a burette used for?
    Delivering a variable volume of liquid with drop-by-drop control — primarily titration. The stopcock allows precise adjustment to find a chemical endpoint that a fixed-volume pipette cannot do.
  • What is the difference between a burette and a pipette?
    A burette delivers variable volumes with continuous control (titration); a pipette transfers one fixed volume repeatably (aliquots, standards). They do different jobs and cannot replace each other.
  • How do I read a burette accurately?
    Read the bottom of the meniscus with your eye exactly level with the liquid surface. Reading from any other angle introduces a parallax error that is consistent and systematic across every titration.
  • What size burette should I use?
    Match the burette size to your expected titration volume. Use the top half of the scale where relative error is lowest. For volumes under 5 mL, a 10 mL or 25 mL burette gives better relative accuracy than a 50 mL one.
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