Objective

To measure the solubility of certain organic solutes in methanol and ethanol by evaporating the solvent from there homogeneous, saturated solutions under reduced pressure at ambient temperature. For a justification of this project see here.

Procedure

A saturated solution of 13 solutes was prepared in six solvents. After centrifuging, 300uL of the supernatant was transferred to two pre-weighed half dram vials. The vials were weighed again and placed in a speed-vac for 10min. The temperature and the vacuum inside the speed-vac was noted. After evaporation for an initial 10min, the vials were weighed and placed back in the speed-vac. After another run for 10min, they were weighed. This process was performed for a third time and each the weights of the vials were recorded in a google spreadsheet. With the information obtained concentration and densities of the saturated solutions were calculated.

Results

Spreadsheet

Discussion

The difference in the weights of the vials after the first evaporation run, when a dry solid was obtained indicated the amount of solid dissolved in the solvent.
According to the Merck index the solubility of vanillin in ethanol is 1:2 vanillin:ethanol and according to the document on Sigma-Aldrich, its solubility in ethanol is 50 mg/ml.
The solubility of Crotonic acid in ethanol at 25°: 52.5% w/w; acetone: 53.0% w/w; toluene: 37.5% w/w.(Merck Index 14th Edn, 2006-2008)
How do these values compare to what you found, after converting to the same units? JCB

In this experiment the solubility of phenanthrene-9-carboxaldehyde is extremely high in methanol (>3 M) but it has repeatedly been found to be much less soluble (for one example of many see EXP169). How is that possible? JCB - Possible sample mix-up.

Also the value for 4-pyrenebutanoic acid is >2M in methanol, which is inconsistent with the results in EXP173 JCB

Based on this mix-up and the very low vanillin measurements - all results in this experiment are flagged as DONOTUSE. JCB


Conclusion

Due to apparent sample mix up results from this experiment are not valid.

Log

2008-10-17

12:30 Weighed 26 (1-26) vials and recorded them in the spreadsheet.

2008-10-22

14:00 Made up saturated solutions of the all solid samples in methanol in one dram vials labeled 1-1 to 13-1. Vanillin took about 6min of vortexing to form a saturated solution in 700uL methanol. Vortexed Phenanthere-9-carboxaldehyde for 5min when, just to make sure that anymore of the solid would not dissolve in the solvent. Pyrene-4-butanoic acid was vortexed for 2min. Boc-methionine formed a gel..the solution became so thick that it could not be vortexed any further.
15:00 Benzaldehyde soluble in methanol in all proportions...found out by transferring 100uL methanol in to a 1dram vial....further added benzaldehyde to this vial in all 5mL of the aldehyde was added to the vial...there was no separation of layers at any point during the addition.
15:30 Cenrtrifuged the one dram vials excluding boc-methoinine and benzaldehyde.
16:15 Transferred 300uL of the supernatant from each vial to pre-weighed half dram vials labeled 1a, 2a, 3a, 4a, 9a, 10a, 11a, 12a, 13a, 14a, 15a, and 16a, soon after transferring the supernatant the vials were tightly capped.
16:45 Obtained a pic of the solutions and supernatants (name the pic here then report it in the results section - for example 210-picA)
17:00 The vials were carefully weighed again without caps.
18:07 Placed the vials in a speed-vac.
18:08 Turned on the vacuum and the rotor of the speed-vac. Time, temperature and vacuum readings recorded during the run were
Time
Vacuum Reading
Temperature C
18:08
1Atm
23.9
18:10
150mTorr
24.8
18:15
140mTorr
25.5
18:18
125mTorr
25.8
18:18 Turned off the speed-vac and removed the vials reweighed the vials.
18:15 After weighing the vials were tightly capped and a pic was taken of these vials.

2008-11-05

11:30 The vials were uncapped and placed in the speed-vac for 10min
11:39 Temp -24.6C (shouldn't be negative JCB) , Vac - 5T
11:40 Removed from the speed-vac and weighed
12:45 Placed the vials again in the speed-vac for 10min
12:55 Temp 26.1, Vac 5T; removed from the speed vac and weighed the vials.


2008-10-23 (this should be a separate experiment - only include runs as part of the same experiments that were done in parallel)

14:20 Weighed out 10 half dram vials and labeled them 27a, 28a, 29a, 30a, 35a, 36a, 39a, 40a, 41a and 42a.
14:35 Prepared saturated solutions of vanillin, phenanthrene-9-carboxaldehyde, 4-pyrene butyric acid, crotonic acid and 4-chlorophenyl acetic acid in ethanol (700uL) in 5 one dram vials labeled 27-2, 29-2, 35-2, 39-2, and 41-2.
15:00 Centrifuged the one dram vials containg saturated solutions, and transferred 300uL of the supernatant to the half dram vials labeled 27a, 28a, 29a, 30a, 35a, 36a, 39a, 40a, 41a and 42a, these vials were tightly capped.
15:20 Half dram vials were weighed without caps. ( 27a, 28a, 29a, 30a, 35a, 36a, 39a, 40a, 41a and 42a.)
15:30 After weighing these vials they were tightly capped.

2008-11-05

1:30 The vials were uncapped and placed in the speed-vac for 10min
11:39 Temp -24.6C , Vac - 5T
11:40 Removed from the speed-vac and weighed
12:45 Placed the vials again in the speed-vac for 10min
12:55 Temp 26.1, Vac 5T; removed from the speed vac and weighed the vials.


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