A burette (or “buret”) is a handy lab tool for dispensing fluids into solutions and, more importantly, for measuring how much fluid you’ve dispensed. They’re a bit unlike other graduated (or marked) lab containers, though, in that their measurements are written from the top down, and they don’t actually measure how much fluid is currently inside them. We’ll show you exactly how to read one, and give you plenty of tips to make sure your reading is accurate every time.
Quick Guide to Reading a Burette
Read a burette from the bottom of the meniscus, or the “U” shape at the surface of the liquid. Make sure your eye is level with the bottom of the meniscus, and take your reading to the nearest 0.05 mL. On a burette, the zero scale is at the top.
Steps
Using a Burette
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Mount and fill the burette with your liquid. In titration experiments, this liquid is the titrant, which you’ll be adding to the beaker. Place your clean burette on its stand and fill it with as much titrant as the experiment requires. [3] X Trustworthy Source Science Buddies Expert-sourced database of science projects, explanations, and educational material Go to source To do this, use a clean funnel, or a squeeze bottle filled with the titrant.
- Note that not every experiment requires a full burette. In fact, most will not.
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Remove any air bubbles in the tip by opening the stopcock. Most burettes operate via a stopcock at the bottom that opens and closes to allow the titrant to flow. Slowly and carefully open the stopcock, turning the handle counterclockwise, until fluid flows through the tip into a waste container, removing any air bubbles. [4] X Trustworthy Source Science Buddies Expert-sourced database of science projects, explanations, and educational material Go to source
- Close the stopcock by turning it the opposite direction, until the handle is perpendicular to the burette.
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Take an initial reading of the burette. Using the methods above, take and record an initial reading of the liquid in your burette to the nearest 0.05 mL, and record this reading on a sheet of paper. [5] X Research source
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Dispense the titrant, and take a second reading. Use the stopcock to dispense titrant into the beaker below according to the instructions of your experiment. Afterward, wait 30-60 seconds for the liquid to settle, then take a second reading to the nearest 0.05 mL. [6] X Trustworthy Source Science Buddies Expert-sourced database of science projects, explanations, and educational material Go to source
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Subtract your initial reading from your second to find apparent volume. Subtract the first reading from the second reading to find how much liquid was dispensed. [7] X Research source This is known as the apparent volume, or “titer” in titration experiments. For example, if your first reading was 10.00 mL, and your second reading was 21.05 mL, then the amount of liquid dispensed is 21.05 - 10.00, which is 11.05 mL.
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Fill the burette to the top, then drain it to the 0.00 mark. Fill your burette with distilled water up to or just below its rim. Then, mount it on its stand and carefully open the stopcock to drain the water so that the meniscus reads “0.00.” Close the stopcock, then gently touch the burette’s spout to the side of the beaker beneath it to dispense any clinging drops. [11] X Research source
- Also, take a temperature reading of the water with a thermometer, which will come in handy in the next steps.
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Wait 5 minutes, then ensure the burette still reads 0.00. If the water has dropped below that mark in those 5 minutes, tighten the stopcock and repeat the first step. If it’s still draining during the 5 minutes, you may have either a faulty stopcock or burette. Replace both and repeat the first step to ensure the stopcock and burette are functioning. [12] X Research source
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Drain 10mL of water into a 100mL beaker, then weigh it. Weigh the beaker first and note its initial mass to the nearest 1 mg. Then drain 10mL of water from the burette into the beaker, touching the burette’s tip to the beaker’s walls and waiting 30 seconds for water in the burette to drip down to the meniscus. Take a second reading to the nearest 0.05 mL, then weigh and record the mass of the beaker again. [13] X Research source
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Find the apparent volume and mass of the water. Subtract your first burette reading from the second to find your apparent volume. Then subtract your first weight reading of your beaker from the second reading to find the mass of water in the beaker that corresponds to this apparent volume reading. [14] X Research source
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Convert the mass at-temperature into true volume. Water’s volume changes with the temperature, so use an online true volume chart to convert the apparent volume you found into true volume. To do this, find the temperature of your water on the chart, then multiply the mass of water in the beaker by the corresponding corrected volume on the chart.
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Subtract the apparent volume from the true volume to find your correction value. The true volume is the value you found by multiplying your data by the corrected volume on the chart. Subtract the apparent volume from its corresponding true volume value to find your correction value. [15] X Research source
- This correction value may be either positive or negative.
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Repeat the calibration to confirm your correction value. Drain the burette down to 20mL, take a reading, then weigh the beaker, and find the correction value for this new set of data. Do the same for the 30 mL mark, 40, 50, and so on, until all the liquid is drained, weighing and recording the new mass of the beaker after every interval, and finding the corresponding correction value. [16] X Research source
- For a Class A burette, the correction value shouldn’t exceed ±0.05 mL. If it does, the burette may be faulty and unreliable.
- For the most accurate calibration, repeat the entire process up to this point 2 more times.
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Find the average correction value and use it in your experiment. Add every correction value found during your calibration, then divide it by the number of correction values to find the average correction value. For example, if your average correction value is -0.02 mL, then you’ll subtract 0.02 mL from every apparent volume reading in your experiment to find the true volume of water you dispensed. [17] X Research source
Expert Q&A
Tips
- Burettes are used for a wide array of lab experiments, perhaps most notably titrations, in which the amount of a chemical in a solution is calculated by adding a determined amount of another chemical. [18] X Trustworthy Source Science Buddies Expert-sourced database of science projects, explanations, and educational material Go to sourceThanks
- That said, burettes can be used in any experiment that requires careful and controlled dispensation of a liquid.Thanks
References
- ↑ https://www.chemedx.org/JCESoft/jcesoftSubscriber/ChemPagesLab/modules/buret/bretread.htm
- ↑ https://www.chemedx.org/JCESoft/jcesoftSubscriber/ChemPagesLab/modules/buret/bretread.htm
- ↑ https://www.sciencebuddies.org/science-fair-projects/references/titration-tutorial-tips-tricks-for-titrating
- ↑ https://www.sciencebuddies.org/science-fair-projects/references/titration-tutorial-tips-tricks-for-titrating
- ↑ https://raci.org.au/common/Uploaded%20files/Website%20files/School/Titration/A%20Guide%20to%20Titration%20(Updated%20Feb%202020).pdf
- ↑ https://www.sciencebuddies.org/science-fair-projects/references/titration-tutorial-tips-tricks-for-titrating
- ↑ https://raci.org.au/common/Uploaded%20files/Website%20files/School/Titration/A%20Guide%20to%20Titration%20(Updated%20Feb%202020).pdf
- ↑ https://www.chemedx.org/JCESoft/jcesoftSubscriber/ChemPagesLab/modules/buret/bretread.htm
- ↑ https://raci.org.au/common/Uploaded%20files/Website%20files/School/Titration/A%20Guide%20to%20Titration%20(Updated%20Feb%202020).pdf
- ↑ https://raci.org.au/common/Uploaded%20files/Website%20files/School/Titration/A%20Guide%20to%20Titration%20(Updated%20Feb%202020).pdf
- ↑ https://chem.libretexts.org/Ancillary_Materials/Demos_Techniques_and_Experiments/General_Lab_Techniques/Calibration_of_a_Buret
- ↑ https://chem.libretexts.org/Ancillary_Materials/Demos_Techniques_and_Experiments/General_Lab_Techniques/Calibration_of_a_Buret
- ↑ https://www.chem.fsu.edu/chemlab/chm3120l/intro/procedure.html
- ↑ http://www2.csudh.edu/oliver/che230/labmanual/calbur.htm
- ↑ http://www2.csudh.edu/oliver/che230/labmanual/calbur.htm
- ↑ https://www.chem.fsu.edu/chemlab/chm3120l/intro/procedure.html
- ↑ http://www2.csudh.edu/oliver/che230/labmanual/calbur.htm
- ↑ https://www.sciencebuddies.org/science-fair-projects/references/titration-tutorial-tips-tricks-for-titrating