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Solubility book (3rd Edn)
Testing the solubility of vanillin in ethanol and methanol at room temperature using a slightly longer time for vortexing to test true saturation point
This experiment seeks to determine whether a longer vortexing time affects saturation. The original intention of the experiment was to vortex for 5 -10 minutes, but a problem during carrying out the solubility measurements meant I wasn't able to (explained below in the time log).
Two 1.5 mL microcentrifuge tubes were weighed and labelled with planned contents. Two 2 mL microcentrifuge tubes were labelled with their planned contents. To one tube was added 750 µL ethanol and to the second 750 µL methanol. Vanillin was added to each tube and the tubes vortexed for about 10 seconds in total (see log for full explanation). The vanillin was found to have dissolved in both samples so more was added. The Vanillin in ethanol mixture was vortexed for 1 minute in 10 second intervals split by 1-2 seconds. At this point the solution appeared to be saturated. The vanillin in methanol solution had dissolved on standing so more vanillin added and the solution vortexed for 1 minute in 10 second intervals as before. This process was repeated until solutions were both deemed to be saturated (both solutions had been vortexed for at least 3 minutes in total).
The saturated solutions were centrifuged for one minute in an Eppendorf 5415D centrifuge at 13,200 rpm/16,100 g. 500 µL of the supernatant from each solution was added to it's respectively labelled eppendorf and dried in the speedvac vacuum centrifuge for 3 hours at room temperature (speedvac does not list rotor speed and is just on/off). Samples were removed and weighed before being returned to the speedvac for further drying until [almost] constant weight.
Full measurements can be found in the spreadsheet here
Thursday 20.11.08 GMT
11.38 - Recorded mass of two 1.5 mL microcentrifuge tubes ("eppendorfs").
11.41 - Added 750 µL of ethanol to a 2 mL microcentrifuge tube.
11.44 - Added 750 µL of methanol to a 2 mL microcentrifuge tube.
11.46 - Added 4 [narrow] spatula scoopfuls of vanillin to each tube.
11.47 - Sellotaped tubes to vortex and started it.
Tubes flew off vortex approx 5 seconds later.
11.50 - Re-attached tubes to vortex in a slightly different place and started it.
Tubes flew off 5 seconds later and hit me with no damage to tubes.
Gave up on attaching to vortex.
11.51 - Noticed both solutes had fully dissolved. Added another 4 spatula scoopfuls of vanillin to each tube.
11.53 - Vortexed vanillin in ethanol solution for 1 minute in 10 second intervals separated by 1-2 seconds. Solution apparently saturated.
11.56 - Noticed that vanillin in methanol had dissolved on standing. Added 4 spatula scoopfuls of vanillin to tube.
11.58 - Vortexed vanillin in methanol solution for 1 minute in 10 second intervals as stated before.
11.59 - Vanillin in methanol solution apparently saturated.
12.00 - Vortexed vanillin in ethanol for 1 minute in 10 second intervals as stated before. Solution still apparently saturated.
12.02 - Vortexed vanillin in methanol for 1 minute as before. Found solution was not saturated.
12.04 - Added 4 spatula scoopfuls of vanillin.
12.05 - Vortexed vanillin in methanol solution for 2 minutes in 10 second intervals.
12.08 - Vortexed vanillin in ethanol solution for 1 minute as before. Solution definitely still saturated.
12.10 - Vortexed vanillin in methanol solution for 1 minute as before.
12.11 - Concluded vanillin in ethanol solution was saturated and vanillin in methanol solution appeared to be saturated.
12.13 - Vortexed vanillin in methanol solution for 1 minute as before.
12.15 - Concluded both solutions were saturated, therefore centrifuged for 1 minute.
12.17 - 500 µL of each solution added to it's respective 1.5 mL eppendorf.
12.18 - Transferred eppendorfs to speedvac.
12.19 - Speedvac started.
15.24 - Samples removed from speedvac.
15.26 - Samples weighed.
15.28 - Samples returned to speedvac for further drying.
16.31 - Samples removed from speedvac.
16.35 - Samples weighed.
16.38 - Samples returned to speedvac.
17.22 - Samples removed from speedvac
17.23 - Samples weighed and deemed to be dry (mass lost <1 mg)
The results of the calculations give the solubility of vanillin in ethanol as 2.48 M and vanillin in methanol as 4.15 M. This finally gives excellent correlation with exp207, which measured the solubilities as 2.5 and 4.19 M respectively.
I will need to try and repeat this experiment with the solvents at higher temperatures so that I get the most accurate solubility at each temperature to find whether there is any correlation between temperature and solubility.
Solubility of vanillin in methanol
(solubility data viewer)
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