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list of experiments
Solubility book (3rd Edn)
To determine the solubility of
Make saturated solutions of
and measure solubility using the gravimetric method.
Measuring the volume of the saturated supernatant was not as accurate with a graduated cylinder as with a 1-mL volumetric flask. Therfore, more saturated solution will be made next time so that there will be at least 1-mL solution. Also, the solution may have been supersaturated. Therefore, next time the supernatant solution will be sonicated before transferring to the volumetric flask.
The solubility of Ugi 234 was determined to be 0.23
16.00 - Dessicated Ugi 234 in vacuum dessicator
16.19 - Added about 1.5-mL 100% ethanol to the Ugi 234 vial while hot water bath was heating to 50 dC
16.21 - Weighed 1-mL voloumetric flask (18.518 g)
16.30 - Inserted Ugi 234 vial into hot water bath (50 dC) (
) [looks like you have an open vial in a water bath - ethanol can absorb water vapour very easily.
[You should seal it - just make sure you don't get within 20C of the solvent's boiling point (that's the rationale for heating to 40C in general.. When you handle the vials always make sure they point away from your face too. JCB]
The vial was sealed with a screwcap. The holder was blocking it in the picture. The temperature was initially at 50 dC, but was about 42 dC when I removed the vial.
17:30 - Removed vial from hot water bath (42 dC) letting it cool to room temperature (22 dC) (
[I can see solid at the bottom - did you notice more solid coming out as it cooled? If you have access to a sonicator put in there for a few seconds to avoid supersaturation - we have been seriously misled by this several times JCB]
I didn't visibly see anything precipitating out as it cooled.
18.00 - Transferred supernatant to 1-mL volumetric flask. However, there was less than 1-mL of supernatant (
[Since you added 1.5 mL of solvent do you think it evaporated despite the cap on the vial? JCB]
I think it vaporized, and was released when the vial was opened.
18.09 - Weighed 10-mL graduated cylinder (28.098 g)
18.20 - Transferred saturated solution to graduated cylinder up to 0.8-mL mark and weighed (28.664 g) (
[Cool- even though the 0.8 mL is not very accurate try to calculate the density to see if you can get a solubility value from that as well JCB]
18.30 - Left to dry in fume hood. Note: This experiment will be redone with enough solution to fill the 1-mL volumetric flask.
17.30 - Weighed evaporated solute in graduated cylinder (28.205 g).
Ugi Product 234 in Ethanol
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