How to Read a Buret Measurement

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A burette (or “burette”) is a handy laboratory tool for dispersing liquids into solutions and, more importantly, measuring the amount of liquid you’ve dispersed. However, they are slightly different from other graduated (or labeled) laboratory containers in that their measurements are written from the top down, and do not actually measure how much liquid is currently in them. We’ll show you how to read one accurately and give you tons of tips to make sure your reading is accurate every time.

Read with the burette from the bottom of the meniscus or “U” shape on the surface of the liquid. Make sure your eye is level with the bottom of the meniscus and read to the nearest 0.05 mL. The burette has a zero scale at the top.

1. 

   Mount and fill the burette with your liquid. In titration experiments, this liquid is the titrant, which you will add to the beaker. Place a clean buret on the rack and fill it with as much titrant as needed for the experiment.[3]
   To do this, use a clean funnel or a squeeze bottle filled with titrant.

   • Note that not every experiment requires a full burette. In fact, most won’t.

2. Remove any air bubbles in the top by opening the stopcock. Most burettes operate via a stop valve at the bottom that opens and closes to allow titrant flow. Slowly and carefully open the stop valve by turning the handle counterclockwise until the fluid flows through the tip into the waste container, removing all air bubbles.[4]

   • Close the stop valve by turning it in the opposite direction until the handle is perpendicular to the burette.

3. First read the burette. Using the above methods, take and record the initial reading of the liquid in the burette to the nearest 0.05 mL and record that reading on a sheet of paper.[5]

4. Dispense the titrant and read again. Using the stopcock, dispense the titrant into the beaker below as directed by your experiment. After that, wait 30-60 seconds for the liquid to settle, then read again to the nearest 0.05 mL.[6]

5. Subtract the initial reading from the second to find the apparent volume. Subtract the first reading from the second reading to find out how much fluid was drained.[7]
   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 fluid drained is 21.05 – 10.00, which is 11.05 ml.

1. 

   Fill the burette to the top, then drain to the 0.00 mark. Fill your burette with distilled water to or just below the rim. Then place it on the stand and carefully open the water tap so that the meniscus reads “0.00”. Close the stopcock, then gently tap the spout of the burette against the rim of the beaker below it to dislodge any stuck droplets.[11]

   • Also, measure the temperature of the water with a thermometer, which will come in handy in the next steps.

2. Wait 5 minutes and then ensure the burette still reads 0.00. If the water has dropped below that mark in those 5 minutes, tighten the stop valve and repeat the first step. If it continues to flow for 5 minutes, you may have a faulty stop valve or burette. Replace both and repeat step 1 to ensure the stop valve and burette are working.[12]

3. Drain 10 mL of water into a 100 mL beaker, then weigh. First, weigh the beaker and record its initial mass to the nearest 1 mg. Then drain 10 mL of water from the burette into the beaker, touching the tip of the burette to the wall of the beaker and waiting 30 seconds for the water to drip from the burette to the meniscus. Read a second time to the nearest 0.05 mL, then weigh again and record the mass of the beaker.[13]

4. Determine 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 reading of the weight of your glass from the second reading to find the mass of water in the glass that corresponds to this apparent volume reading.[14]

5. Convert the mass at temperature to the correct volume. The volume of water changes with temperature, so use an online actual volume chart to convert the apparent volume you found to actual volume. To do this, find the temperature of your water on the chart, then multiply the mass of water in the glass by the corresponding corrected volume on the chart.

6. Subtract the apparent volume from the actual volume to find the correction value. The true volume is the value you found by multiplying the data by the corrected volume on the chart. Subtract the apparent volume from its corresponding true volume value to find the correction value.[15]

   • This correction value can be positive or negative.

7. Repeat the calibration to confirm the correction value. Empty the burette to 20 mL, read, then weigh the beaker and find the correction value for this new data set. Do the same for the 30 mL mark, 40, 50, and so on, until all the liquid is drained, weighing and recording the new weight of the beaker after each interval and finding the appropriate correction value.[16]

   • For a class A burette, the correction value should not exceed ±0.05 mL. If it does, the burette may be faulty and unreliable.
   • For the most accurate calibration, repeat the entire procedure up to this point 2 more times.

8. Find the average correction value and use it in your experiment. Add each correction value found during calibration, then divide by the number of correction values ​​to get the average correction value. For example, if your average correction value is -0.02 mL, then you will subtract 0.02 mL from each apparent volume reading in your experiment to find the true volume of water you dropped.[17]

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Source: HIS Education