Step‑by‑Step Burette Calibration: A Practical Guide for Accurate Titrations

If you have ever watched a titration go sideways because the burette read “0.00 mL” when the solution was already half‑full, you know how frustrating a bad calibration can be. In the lab, a small error in volume can turn a perfect experiment into a confusing mess. That is why, right now, getting your burette calibrated correctly is more important than ever—especially as many of us are teaching hybrid classes and need reliable data to show students online.

Why Calibration Matters

A burette is the workhorse of any titration. It delivers liquid drop by drop, and the whole point of a titration is to know exactly how much of a reagent you have added. If the scale on the burette is off by even 0.05 mL, the calculated concentration of your unknown can be off by a few percent. In analytical chemistry we call that “systematic error,” and it is the kind of error that cannot be fixed by repeating the experiment. Calibration removes that hidden bias and gives you confidence that the numbers you report truly reflect the chemistry happening in the flask.

What You Need Before You Start

A clean, dry burette (the one you plan to use for the titration)
A class A volumetric flask (50 mL or 100 mL) – these are the most accurate containers we have in the lab
Distilled water at room temperature
A balance that can read at least to 0.01 g
A small funnel and a piece of filter paper
A notebook or a lab notebook app (I keep a running log in Lab Standard Burettes for every calibration)

Make sure all glassware is free of oil or dust. A single drop of oil can change the surface tension and affect how the water climbs the burette wall, leading to a false reading.

Step 1 – Rinse and Fill

Rinse the burette with distilled water three times.
Fill the burette about three‑quarters full with the same distilled water you will use for the calibration.
Open the stopcock and let a few drops run through the tip to remove any air bubbles.

Pro tip: I always tap the side of the burette gently after filling. It sounds silly, but it helps any tiny bubbles cling to the glass and rise out of the way.

Step 2 – Zero the Burette

Place the burette on a stable stand and make sure the stopcock is closed. Read the meniscus (the curved surface of the water) at eye level and note the volume. Adjust the stopcock until the reading is exactly 0.00 mL. This is called “zeroing” the burette.

If you cannot get a perfect zero, record the reading you do get and use it later as a correction factor. Most modern burettes have a fine‑threaded stopcock that lets you make tiny adjustments, so don’t rush this step.

Step 3 – Deliver a Known Volume

Now we will deliver a known volume of water into a pre‑weighed volumetric flask.

Place the empty flask on the balance and tare it (set it to zero).
Open the burette stopcock and let water flow until the burette reads 25.00 mL (or any convenient volume you prefer).
Close the stopcock and quickly transfer the flask to the balance. Record the mass of the water collected.

Because the density of water at room temperature is very close to 1 g/mL, the mass in grams is essentially the volume in milliliters. For example, if you collected 24.87 g of water, you have delivered 24.87 mL.

Step 4 – Calculate the Correction

Here’s the simple math:

Observed volume (mL) = mass of water (g) / density of water (g/mL)
Correction factor = Expected volume – Observed volume

If you expected 25.00 mL but observed 24.87 mL, the correction factor is +0.13 mL. That means every time you read the burette, you need to add 0.13 mL to get the true volume.

Step 5 – Verify the Calibration

A single measurement can be lucky or unlucky, so repeat the delivery at least two more times, using different target volumes (e.g., 10.00 mL and 40.00 mL). Plot the observed volumes against the expected ones; the line should be close to a 45‑degree slope. If the points stray far from the line, clean the burette again and repeat the whole process.

In my own lab, I once found a stubborn 0.2 mL offset that only showed up when I tried to deliver more than 30 mL. A quick second rinse and a careful check of the stopcock solved it. That little episode reminded me why I keep a calibration log in Lab Standard Burettes – it saves time when the same issue pops up later.

Step 6 – Document and Use the Factor

Write the correction factor in your lab notebook, along with the date, the temperature of the water, and the person who performed the calibration. When you run a titration, simply add the factor to every burette reading before you calculate concentrations.

If you are teaching a class, share the factor with your students and ask them to repeat the calibration on their own burettes. It’s a great way to show how small systematic errors can creep into data and how we can catch them early.

Common Pitfalls and How to Avoid Them

Air bubbles in the tip: They act like tiny pockets of air that compress under pressure, giving a lower volume reading. Always purge the tip before zeroing.
Temperature changes: Water expands about 0.02 mL per degree Celsius. If you calibrate at 22 °C and titrate at 30 °C, you will introduce error. Record the temperature and, if possible, calibrate at the same temperature you will use for the titration.
Dirty stopcock: Residue can cause the stopcock to stick, making it hard to get a precise zero. Clean it with a small brush and a bit of ethanol before each calibration.

When to Re‑Calibrate

After any major cleaning or after the burette has been stored for a long time.
Whenever you notice a drift in titration results (e.g., repeated runs give different endpoint volumes).
At the start of a new semester or when a new batch of reagents arrives.

A quick 10‑minute calibration check can save hours of re‑running experiments later.

Closing Thoughts

Burette calibration may feel like a routine chore, but it is the backbone of accurate titration work. By following these steps, you turn a potential source of error into a reliable part of your workflow. In the end, the extra few minutes you spend at the balance translate into confidence in every data point you report.

Remember, the goal of Lab Standard Burettes is not just to teach you how to use equipment, but to help you trust the numbers you generate. A well‑calibrated burette is a quiet partner that lets the chemistry speak for itself.