Today, I made my first attempt at a real project.
I followed the procedure on the wiki to prepare salicylic acid from acetylsalicylic acid (aspirin.)
All went well until the step which calls for the solvent (acetone) to be boiled off to extract the ASA. The acetone boiled off fine, but the beaker
tipped over on the hotplate, spilling the acetone. Luckily, most of the ASA had already crystallized out, making recovery quite easy. However, like an
idiot I decided to further heat the ASA to dryness. I assumed that, if the procedure called for it to be boiled to dryness, it would not matter how
long I heated it. However, the crystals turned to a liquid, which solidified when removed from heat.
Now, All I have is a small amount of crystals (which I discarded as a pointlessly small amount to reflux), and a beaker full of organic tar.
So what happened? Did the ASA melt, or did it just decompose?
Also, how can I clean the tar out of the beaker? Anyone else have this experience.Ubya - 7-6-2020 at 14:35
in general, don't bring to dryness organic compounds on a hotplate, it's easy to burn something, use a water bath or a steam bath to remove the last
bit of water.
you melted and burned the ASA
to clean your beaker you could try with a strong solution of sodium hydroxide, as a last resort there's the piranha solution but it's really dangerousreactofurnace - 8-6-2020 at 05:45
As @ubya stated the ASA decomposed, due to excessively high temps.
The acetone step is really only needed to extract the ASA. If salicylic acid is your end goal that step can be omitted completed. Just dissolve the
tablets in water and filter off the filler components. (you may boil down the mixture and recrystallize if you deem necessary) Finally, you can
hydrolyze the ASA with HCl. Then recrystallize in water or acetone.
Keep trying and stay safe
[Edited on 8-6-2020 by reactofurnace]Chemorg42 - 8-6-2020 at 07:44
OK, thanks for the help.
To clean my glassware, I will probably use a sodium hydroxide solution.
However, how should I clean the tar from my testtube brush? What about from a metal spoon?Ubya - 8-6-2020 at 08:04
OK, thanks for the help.
To clean my glassware, I will probably use a sodium hydroxide solution.
However, how should I clean the tar from my testtube brush? What about from a metal spoon?
Use a metal sponge to clean the metal spoon, just a bit of elbow grease.
About the testube brush, i would try with hot water at the beginning, to remove as much water soluble compounds as possible, if the tar is still stuck
to the brush, i would try the sodium hydroxide solution but i'm not sure about the corrosion of the plastic partsChemorg42 - 8-6-2020 at 14:53
Just a quick note for the record, sodium hydroxide solution completely cleaned the beaker. Also, my test tube brush was not effected by the solutionUbya - 8-6-2020 at 15:17
Also, my test tube brush was not effected by the solution
i don't know how to solve that, piranha will eat the plastic like candy flossChemorg42 - 8-6-2020 at 15:43
@Ubya, sorry, I was not clear at all.
What I meant was, the brush was cleaned, and concerns about sodium hydroxide damaging the plastic were unfounded (at least at this concentration and
this particular plastic.)Ubya - 8-6-2020 at 16:50
