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Measure volume · Chemistry

Burette

Burette, with labels: scale in cm³, 0 at the top, meniscus, tap, jet.

What it is for

A burette is a long glass tube with a scale and a tap. Read the level before and after you run solution out; the difference is the volume added.

Capacity
50 cm³, with 0.00 at the top
Smallest division
0.1 cm³
Record to
the nearest 0.05 cm³, e.g. 12.35 cm³ (two decimal places, as taught here); one precision in a table

Why choose it

For adding a solution a little at a time and knowing exactly how much went in, as in an acid–alkali titration. A measuring cylinder reads only to about 1 cm³, and a volumetric pipette gives one fixed volume, so a titration uses the pipette for the solution in the flask and the burette for the one you add.

How to read it

11121314eye too high:parallax erroreye level:12.35 cm³0 is at the top:numbers go down
  1. Clamp it upright and run a little solution through the tap, so no air is left below it.
  2. Take out the filling funnel and hold a white card behind the scale.
  3. Remember the scale counts down from 0.00 at the top: the numbers grow as the level falls.
  4. Read the bottom of the meniscus, eye level with it, to the nearest 0.05 cm³: 12.35 cm³.

Exam-style question

A conical flask holds 25.0 cm³ of sodium hydroxide solution and a few drops of thymolphthalein. In the first accurate titration the burette of hydrochloric acid reads 0.00 cm³ at the start and 12.35 cm³ at the end-point; in the second it reads 12.35 cm³ at the start and 24.60 cm³ at the end-point.

  1. Calculate the volume of acid added in each titration.
  2. Calculate the mean titre to two decimal places.
  3. How does the student know the end-point has been reached?
Show what a good answer says
  1. 12.35 − 0.00 = 12.35 cm³ and 24.60 − 12.35 = 12.25 cm³.
  2. (12.35 + 12.25) ÷ 2 = 12.30 cm³. The two titres agree within 0.10 cm³, so both are used.
  3. Thymolphthalein turns from blue to colourless and stays colourless when the flask is swirled; near the end the acid is added drop by drop.

Teaching points for checking your own answer, not official Cambridge marks.

Common errors

  • Reading the top of the meniscus, or with your eye above or below it (parallax error).
  • Leaving the funnel in the top or an air bubble below the tap: the reading then changes without solution reaching the flask.
  • Reading the scale upwards: it counts down from 0.00, so a level just below the 12 mark is 12.05, not 11.95.
  • Mixing precisions in one results table (12.3, then 24.60), or dropping a needed final zero (24.6 for 24.60 cm³).

Where you use it here

No experiment on the site uses it yet; more are on the way.

From the Practical Test apparatus lists of the Cambridge IGCSE Biology 0610, Chemistry 0620 and Physics 0625 syllabuses for 2026–2028, and the apparatus the experiments on this site use.

More in “Measuring instruments”