Researcher

Evan Curtin

Objective

To calculate the solubility of salicylic acid in chloroform, water and acetonitrile by density method. The additivity of volumes is an assumption and the density of the solid is obtained from ChemSpider prediction.

Results

Google Spreadsheet - Exp198 - 1
The solubility of solutions concentrated with salicylic acid was found to be:
For 1mL Chloroform: -3.35 M
For 1mL Water: -0.384 M
For 2mL Water: 0.08 M
For 5mL Water: -0.017 M
For 1mL Acetonitrile: 0.2387 M
For 2mL Acetonitrile: 0.3785 M
For 5mL Acetonitrile: 0.3353 M

Results for 2mL and 5mL Chloroform solutions couldn't be measured due to lack of pure solution.

Discussion

Salicylic acid in Chloroform
The solubility of the solution in chloroform was determined to be -3.35 M. Solid salicylic acid was floating on top of the solvent, chloroform. As a result, a sample of solution with no solid wasn't extracted. For future experiments, the solid should be filtered out of the solution. Additionally, the densities of salicylic acid and chloroform are very close [numbers - EMC]. As a result, a small amount of experimental error can cause a very large difference in calculated molarity. The density method isn't an effective way of measuring this solubility. The solubility could be better determined by NMR method. [Link to previous experiments - low concentration and ranges - EC]
Salicylic acid in Water
Previously determined solubilities of salicylic acid in water have an average of .0138M. The very low solubility makes it more difficult to accurately determine the solubility in this experiment. However, the values in this experiment are negative for molarity. The values for solubility in water are erroneous and should be excluded. [Link to previous values - EC]
Salicylic acid in Acetonitrile
The acetonitrile solution appeared to have an "extremely small" amount of solid after cooling. However, there was no clear indication of crystal formation. It is possible that no crystals had formed. The previously determined solubility of salicylic acid in acetonitrile was 0.55M. The molarity determined in this experiment was 0.3353M. The solution of salicylic acid in acetonitrile was not saturated.

Conclusion

The concentrations determined in this experiment were invalid.

Log

2011-01-20
14:42 - Bath set to 40C, current temperature is 25C
15:00 - Prepared mixtures of Salicylic acid in chloroform(sample 1), water(sample 2), and acetonitrile(sample 3) in 20mL twist cap tubes. There was solid material at the bottom of each tube.
15:16 - Added mixtures to bath, temperature of bath is 40C
15:25 - Measured the mass of 1mL, 2mL, and 5mL volumetric flasks. Measured the mass of the flasks with pure solvent.Rinsed flasks with acetone and dried with air between solvents.
16:09 - Bath temperature is 40c
16:25 - Removed tubes from bath, decanting immediately. Sample 1 Had solids floating at the top which moved with the liquid into the new container (this could cause some sort of error)
Sample 2 has a small amount of visible solid. Sample 3 has no visible solid.
16:29 - Changed temperature of bath to 25C
16:37 - Temperature of bath is 37.5C
16:41 - Temperature of bath is 33.5C
16:52 - Temperature of bath is 27.5C. All samples have visible solid, sample 3 has an extremely small amount of solid.
17:02 - Temperature of bath is 25C. Moved all samples into the bath
17:22 - Temperature of bath is 25C
17:42 - Removed samples from bath, immediately decanted into clean tubes. Weighed empty volumetric flasks as well as flasks with solution. Not enough chloroform solution could be extracted without getting solid salicylic acid to measure the 2mL or 5mL flasks.