Objective

To measure the solubility of benzoic acid (Chemspider), in methanol (Chemspider). For a justification of this project see here.

Procedure

Saturated solutions are made of benzoic acid (Chemspider), in methanol (Chemspider), by charging a one dram vial with 700μl of the solvent.
The solute is then added in subsequent amounts until the solution has reached a clear point of visible saturation. Each vial is vortexed for 30 seconds. After the process of vortexing is complete, each vial is centrifuged for one minute. 300μl of the mother liquor is then pipetted into pre-weighed half-dram vials. The solution is weighed and entered into the speedvac, noting the pressure,. The solution is then re-weighed after all of the liquid has evaporated off. The results can be found on the following Spreadsheet.

see comments for EXP009 and wrap this experiment up JCB

Log

2008-11-4

14:36 Charged two dram vials with 700μl of methanol.
14:42 Added benzoic acid to first vial.
14:45 Added small amounts of benzoic acid four times and vortexed for 30 seconds each time; until saturation was reached.
14:51 Saturated second vial.
14:52 Labeled each vial "Benzoic acid M1 & Benzoic acid M2", respectively. (EXP005_p1.jpg)
14:54 Placed both vials in centrifuge for 1 minute.

2008-11-6

14:00 Vortexed both vials to re-ascertain that saturation had been reached from previous session.
14:04 Micropipetted 300μl of solution from each vial, and charged them to two new half-dram vials.
14:11 The uptake of 300μl of solution into micropipette had residue of solute within; which was visibly seen as crystals were produced within the new half-dram vials. (EXP005_p2.jpg)
14:12 Crystallized half-dram vials were thrown away.
14:14 An additional 700μl of methanol was added to the "Benzoic acid M1& Benzoic acid M2" dram vials.
14:15 Vortexed both dram vials for 30 seconds. All of the solute dissolved in both of the now 1400μl methanol-filled dram vials.
14:17 Additional solute was added to both vials and vortexed for 30 seconds until saturation was reached.
14:22 Centrifuged both vials for 1 minute.
14:32 Weighed 2 new half-dram vials.
14:38 Re-vortexed and centrifuged dram vials. (Caution- Benzoic acid in methanol will begin to crystalize if left alone for a couple of minutes.)
14:40 Pipetted 300μl of solution into weighed half-dram vials. (EXP005_p3.jpg)
14:50 Weighed both half-dram vials containing solution.
14:52 Place both half-dram vials into speed vac. (Allowed rotor to get up to speed before turning on the vacuum pump. You need to note the time you started rotor and the time you turned on the vac pump if more than one minute JCB)
14:55 Pressure was gauged at 5Torr during speed vac process.
15:15 Speed vac process was stopped.
15:30 Ran the speed vac process again for 10 minutes (Pressure gauged at 5Torr during speed vac process.- the pressure will change over the course of the evaporation so you need to say exactly when you observed it - you should take a reading a few minutes after putting the samples in and right before removing them at the very least JCB)
15:43 Weighed both dry vials. (EXP005_p4.jpg) also why would there be a film near the top of the vial in this pic? JCB

Tags


Compound
Inchi Key
Inchi
Benzoic acid
WPYMKLBDIGXBTP-UHFFFAOYAD
InChI=1/C7H6O2/c8-7(9)6-4-2-1-3-5-6/h1-5H,(H,8,9)
Methanol
OKKJLVBELUTLKV-UHFFFAOYAX
InChI=1/CH4O/c1-2/h2H,1H3