Evan Curtin


To calculate the solubility of 2-phenylbutyric acid in methanol by density method. The additivity of volumes is an assumption and the density of the solid is obtained from ChemSpider prediction.


Make a saturated solution of 2-phenylbutyric acid in methanol. Do this by mixing the solute into the solvent. Heat to around 40-45C. If all solid dissolved, let sit on counter. If there is still solid remaining, decant immediately into a clean container and let the supernatant sit on counter. Let solution stand to equilibriate. If the solid precipitates, decant the supernatant. This is a saturated solution. If there is no solid, evaporate solvent slowly using air (be careful that the temperature doesn't drop too low). Once solid precipitates, decant the solution. This is saturated.

Measure the density of pure solvent by weighing in a volumetric flask (try to get at least 1mL and 2mL). Using these same flasks, measure the density of the saturated solution by weighing. Make sure the flask is clean before weighing each time. Enter density values in the spreadsheet in the results section.


Measured Solubility of 2-phenylbutyric acid in methanol.


After both solutions of 2-phenylbutyric acid were heated, no solid remained or precipitated out for the rest of the experiment. Sample 2 (3.5289g solute in 1mL of solvent) still remained in solution despite the large amount of solute relative to solvent. Since no solid precipitated out of solution, a saturated solution was not made. Even when the solution was 5.33 M, no solid precipitated out. In addition, while heating, the solution's temperature rose above the melting point for 2-phenylbutyric acid and no layers were visible. Also, previously obtained data shows that 2-phenylbutyric acid is very soluble in ethanol, and it can be assumed that it should also be very soluble in methanol. Because of these factors, 2-phenylbutyric acid is most likely miscible with methanol.


2-phenylbutyric acid is soluble in all proportions, or miscible, with methanol. The theoretical molarity of a solution that is 100% 2-phenylbutyric acid is 6.638M. Therefore the solubility of 2-phenylbutyric acid in methanol is 6.638M.


14:14 - Turned bath on to 40C, current temperature 25C
14:40 - Made solution of 3.5581g of 2-phenylbutyric acid and 3mL of methanol (labeled 1). The solute completely dissolved at room temperature.
14:45 - Bath temperature 26C. Set temperature of a roto-vap machine to 45C. Added warm water to the basin. Put water in a large beaker, let sit on counter.
14:50 - Made solution of 3.5289g of 2-phenylbutyric acid and 1mL of methanol (labeled 2). The solute dissolved partially, there was some remaining solid.
15:45 - Added both solutions 1 and 2 to bath (the basin of the roto-vap). Current temperature 47C
16:10 - Bath is 47C
16:30 - Measured masses of pure methanol in 1mL and 2mL volumetric flasks. Bath temperature 49C
17:10 - Bath 49C
17:20 - Bath 50C. Removed tubes from bath. No solid was visible. No layers visible. Placed tubes in room temperature bath (water in large beaker). Temperature 25C
18:20 - Removed liquid solution from tubes (no solid formed at the bottom). Massed the solution in 1mL and 2mL volumetric flasks.