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tom haggen
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Well today I evaporated off the remaining isopropyl which was mixed with acetylsalicylic acid. I got some pretty awsome crystal formations. what do
you guys think?
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Geomancer
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Yesterday and today, I recrystalised two batches of asprin, one of 13g and one of 68.25g. No undue problems were encountered. I will give the
procedure for the second batch.
The tablets were crushed until they were mostly powder, then added to 100mL of boiling ethanol. The ethanol was again heated to boiling, and
filtered through two coffee filters with a small amount of diatomaceous earth deposited (my earlier attempt demonstrated that some stuff gets through
the filters). Even though the assembly was being warmed, some crystaliztion occurred. I washed the filter cake with an aditional 25mL or so of hot
ethanol, though it appears some crystals were still left. Also, some stuff got through the filter even with the DE. I attempted to remove this by
sedimentation and decantation, but this was only partly successfull.
The filtrate is relatively unsaturated, as filtering more saturated solutions proved problematic (think stalagtites, etc.). Crystalization begins
only relatively close to room temperature. After the product had cooled to room temperature( with considerable crystal growth), I added 100mL or so of
cool water. Precipitation was almost instantaneous, with the solution quickly turning opaque and then into slush. The entire jar was involved, so I
added about 20mL more water to make sure I had gotten most of it, and stuck the thing in the freezer. After the solution had cooled, I broke up the
slush and filtered through a single coffee filter. I washed the filter cake with several portions of water (about 100-200mL total). The product is in
the form of needle-like white plates.
Aspirin was from Rite-Aid, lightly coated, 325mg tablets.
Ethanol was from the hardware store, claims to be denatured with methanol.
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Sir Dudalot
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I've always just dissolved my asprin in acetone then filtered and left the acetone out for a day or so to evaporate. This was during the summer
when it was warmer though (aournd 20*C at night). I never had any problems with slow filtering. I bought my asprin at a local drugstore and my
acetone at my local hardware store. Nothing special. No heating involved.
<a href=\"http://www.angelfire.com/falcon/dudalot\">Videos and a few procedures.</a>
\"Dirt is too valuable to just throw away.\" -my dad, and he was serious.
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Geomancer
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I chose to recrystalize rather than simply extracting. No doubt this is just another sign of my latent eletist tendencies.
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roger2003
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Aspirin hydrolysis
For details see:
http://files.irt.drexel.edu/courseweb/ScienceInMotion/newman...
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tom haggen
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My Acetylsalicylic acid was also recrystallized. I think I have been using the term extraction incorrectly lately. Forgive me for my misuse of
terminology.
[Edited on 28-3-2004 by tom haggen]
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Geomancer
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roger2003: Sweet. Interesting that they use acid hydrolysis. I've been using basic hydrolysis.
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roger2003
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The pH-Rate Dependence of the Hydrolysis of Aspirin
details:
http://www.md.ucl.ac.be/pharma/tpao/tpintegres/Cinetique_chi...
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Geomancer
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Here's somthing interesting. A few days ago, I dissolved a bunch of recrystalized ASA in excess base (Red Devil Lye in water). The starting
material had a little phenol red added to help see what was going on. With the addition of enough base, the solution turned reddish, just as it is
supposed to. Today (12:00) I came back to the (hopefully hydrolysed) solution. I added HCl to precipitate the product. The solution quickly turned
yellow, even before most of the precipitation was complete. I continued adding acid until it was clear that I had got everything I was going to get. A
smallish quantity of gas was evolved (this happened the previous time too. I hope it doesn't indicate decarboxylation), and there was a definite
acetic odor (as expected). Around 8:00 I returned to filter off the product. The solution was green. What's up with that?
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Esplosivo
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The acetic odour given off shows that your ASA has been broken down to salicylic acid (also good for making picric acid).
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tom haggen
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Last time I recrystallized asa it reeked of an acetic odor. I used 70/30 isopropyl alcohol. It didn't take any over heating to accomplish this
[Edited on 1-4-2004 by tom haggen]
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Mumbles
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Ok Explosivo, perhaps you should read his post a bit more carefully. He said the acetic odor was expected. I take this to mean that he knows of the
simple concept of hydrolysation. There is no need to pound that into the ground.
As for the green color. My best guess would be that some sort of Chlorosalicylic acid formed perhaps. Maybe the HCl decomposed and there is not Cl
in the liquid. Perhaps the shade of green could help a bit more.
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Esplosivo
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Sorry, my bad. I missed the "as expected" part.
Well, the solution turned green. What was the intensity of the green colour. A pale faint green colouration would mean that there is Cl2 present,
which I doubt since it would have reacted with the salicylic acid right? Could have been any impurity which formed a complex, such as copper
imuprities forming complexes because of the acetic acid and the chloride ions?
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Geomancer
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I'm begining to think the situation isn't half as interesting as I thought it was. The solution was green, alright, a watery emerald green.
But I now think it was contamination, specificly I think the acid solution was corrosive to the stainless steel spoon I had left in it. When I removed
the spoon, I noticed a small amount of pitting and blackish residue as well as a less shiny surface. I dont know much about salycilate complexes, but
I do know iron forms a purple one, so the contaminant isn't iron, or at least not ferric iron. Assuming that the steel is some combination of Fe,
Cr, Ni and Cu, this would mean it's Cr<sup>3+</sup>, no?
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thunderfvck
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Cu+2 is green.
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Geomancer
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| Quote: | Originally posted by thunderfvck
Cu+2 is green. |
Yes, but copper would oxidize any exposed iron.
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Geomancer
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Yesterday I came back to my crude salicylic acid, which I had left out to dry after an incomplete and slow filtration (the white sludge liked the
water more than gravity did). It was still damp, and the galvanized steel mesh I had been supporting it on had corroded badly (duh). I decided not to
waste more time on drying, and dissolved it in the minimum amount of boiling ethanol. The solution immediately turned purple. Whether this was due to
iron from my spoon or from the mesh I don't know. Upon filtration, losses due to premature crystalization were small and manageable, unlike with
my attempts to recrystallize ASA from saturated solution. Crystals apeared to have difficulty nucleating, with initial growth confined to a large,
flat, single crystal on the surface and some growth on the glass around the edges of the solution. Later crystals grew thoughout the solution, and,
apparently, the growth action forced the upper crust a few mm above the liquid level. After it had reached room temperature, I cooled it in the
freezer, and then slowly added an equalish volume of boiling water. I niether observed any sudden crystal formation nor any gross dissolution of
extant crystals. I then cooled and froze to get a few more crystals. I filtered and washed with several portions of ice water. The final portion of
wash water had only a barely detectable lilac tinge. I added a small portion of rust from my ex steel mesh to the final wash water. No immediate color
formation was visable. The crystals are in the form of white needles, with a coarse texture, that drain liquid well. This is different from my earlier
sample, which had a texture vaguely reminiscent of cotton candy. This may be due to different techniques, or to one (or both) of the samples being
contaminated (probably with ASA). For what it's worth, I think that recrystallizing from water would be a better choice, next time.
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thunderfvck
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Hey, wait a minute...Cu +2 is not green...It's blue!
I don't know what I was thinking. Must have been those homosexual tendencies, once again...
Off topic to THIS subject but I don't want to open a whole new thread...I have a copper penny in some HCl, the solution is green. Cu+2 is in
there, yes? CuCl2. Why is it green?
So it wasn't the homosexuality afterall...
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The_Davster
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I believe that copper(II) is green when it it is with a halogen anion. Otherwise it is blue.
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Geomancer
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Homosexuality causes one to see colors wrong? Copper ions change color depending on the ligands that coordinate with them. Chloride is capable of
displacing water from the hexaaqua complex (blueish) to form the tetrachlorobiaqua complex (green) (I may be getting the nomenclature screwed up
here). Bromide and ammonia also give distinctive colors; go to the "Complex Ions of Coppper" thread for more details.
I came back to my final wash water+rust from the previous post this morning. Purple! Apparently it takes some time for the rust to dissolve
sufficiently. Either that or the "homosexual agenda" is alive and well.
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