Calibration of a Buret

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Discussion and Procedure

To carry out this procedure you will require, in addition to a volumetric buret, two clean, dry 125 mL Erlenmeyer flasks and one #5 rubber stopper.

Select a 50 mL buret from the buret cabinet in the north-west corner of the lab. After you have cleaned this buret attach a piece of tape with your name to the open end of the buret. This will serve to identify it. You will be using this buret for this calibration and for the two volumetric analyses. Proceed with the calibration as described below.

1. Disassemble the stopcock, noting carefully how it is assembled, then clean the bore of the buret with a warm solution of Alconox. The teflon stopcock usually does not require much cleaning; however it might be necessary to soak it in warm Alconox solution. Do not use a brush on the stopcock since it will scratch the relatively soft teflon. These scratches are the primary reason for leaking burets. Rinse the buret and stopcock well with water and distilled water. Reassemble the stopcock.

4. While checking the buret, weigh, to the nearest 1 mg, a dry 125 mL Erlenmeyer flask fitted with a #5 rubber stopper. Once the tightness of the buret stopcock has been established, record the level of the meniscus (which should be at 0.00 mL). Run an accurately measured volume of about 10 mL into the weighed flask at a flow rate of approximately 10 mL per minute. Touch the tip to the wall of the flask. Wait 1 minute, record the meniscus level. The difference between the two readings is the "apparent volume". Now stopper the Erlenmeyer flask with the #5 rubber stopper and then weigh it to the nearest 1 mg. The difference between the two weights gives the mass of water equivalent to the apparent volume. Record the temperature of the water in the flask. With the aid of the table below convert this mass of water into the true volume at 20 oC.

Volume occupied by 1.000 g of water weighed in air using stainless steel weights. Corrections for the buoyancy of stainless steel and the thermal expansion of the glass buret have been applied.

T, in oC Volume at T Volume corrected to 20 oC
10 1.0013 1.0016
11 1.0014 1.0016
12 1.0015 1.0017
13 1.0016 1.0018
14 1.0018 1.0019
15 1.0019 1.0020
16 1.0021 1.0022
17 1.0022 1.0023
18 1.0024 1.0025
19 1.0026 1.0026
20 1.0028 1.0028
21 1.0030 1.0030
22 1.0033 1.0032
23 1.0035 1.0034
24 1.0037 1.0036
25 1.0040 1.0037
26 1.0043 1.0041
27 1.0045 1.0043
28 1.0048 1.0046
29 1.0051 1.0048
30 1.0054 1.0052

6. You need not submit a report for this calibration but write in your laboratory notebook the answers to the questions posed below.

Questions on Buret Calibration

1. Your weight of water is converted to the true volume using data from Table 27-3 of SHW. What are the three corrections that are embodied in those values?
2. Explain why it is not necessary to weigh the water samples on the analytical balance.
3. When the glass of a buret expands due to an increase in temperature does the diameter of the bore increase or decrease?
4. Most volumetric glassware is calibrated at what temperature?
5. What do the letters T.D. and T.C., that are found on various types of volumetric glassware, signify?

Contributors

• Ulrich de la Camp and Oliver Seely (California State University, Dominguez Hills).

This page titled Calibration of a Buret is shared under a not declared license and was authored, remixed, and/or curated by Oliver Seely.