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S.C. Wack
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The use of corks was perfectly wise. A cork was included so the ether wouldn't all evaporate from the can during the operation, if the can wasn't
emptied into some fancy ether dispenser. These were quite small cans having no other way to seal them.
The Organikum (generally a good source of different directions) says "It is therefore recommended to store it over potassium hydroxide, which
immediately converts the hydroperoxides produced into insoluble salts and, moreover, is a very suitable drying agent.", but my thinking was this would
be on the surface of the KOH only, and would not occur with peroxide free ether. I guess if something is precipitating regardless (there are other
threads and posters here noting precipitates with KOH) the K is getting into the ether somehow.
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pots-o-potash
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If this case did turn out to be acetaldehyde contamination (or for any situation where that is the issue with ether), it seems that n-butane forms an
azeotrope with acetaldehyde that boils at -7C, so that could be useful for removing it from diethyl ether.
The mixture by weight should be 16% acetaldehyde to 84% n-butane
It's listed on wikipedia's azeotrope tables page:
https://en.wikipedia.org/wiki/Azeotrope_tables#Miscellaneous...
With the citation of:
Reinders, W.; de Minjer, C. H. (3 September 2010). "Vapour-liquid equilibria in ternary systems. V. The system water-formic acid-metaxylene". Recueil
des Travaux Chimiques des Pays-Bas. 66 (9): 564–572.
Commercially available butane refill canisters are normally a mixture of n-butane and isobutane, with enough n-butane to be useful for this purpose.
(isobutane would boil off first, as would any propane added in some blends, though I believe the blends intended for lighter and micro-torch refills
... or butane curling irons, etc, are generally just i-butane and n-butane to keep pressure low enough for relatively thin plastic reservoirs)
isobutane itself might also form an even lower BP azeotrope, but I don't have documentation to source that.
You could sub-cool the ether in a freezer (around 0F or -17.8C) along with a butane canister and inject some of the chilled butane into the chilled
ether to allow a mixture to form before allowing careful warming and boil-off. Given that'd be below isobutane's BP as well, you'd probably have to
keep the butane canister warmer than -11C to allow some pressure to dispense the butane.
Doing it closer to room temp would result in a lot of butane snow forming and enough pressure to make a jet hard enough to potentially splash the
ether, but perhaps close to 0C would be OK (closer to refrigerator temperature) for cooling the butane while the ether could be at freezer temp.
You could rig up a lid or stopper with the appropriately sized hole bored into it for the butane dispenser tip to fit snuggly and avoid air/moisture
ingress during injection. (then carefully allow excess pressure to dissipate and re-seal with the correct lid)
Then just slowly allow the temperature to rise in the fridge, opening it occasionally to release pressure.
Then allow some further warming to allow the excess butane to boil off. (this is less of an issue if the ether's intended use is OK with some butane
contamination, though presence of water, as in azeotropic DEE will likely reduce solubility of butane significantly)
This also assumes that diethyl ether can't form an azeotrope with butane, which would be problematic. But given the absence of references to DEE
forming any azeotropes with other alkanes (like methanol, ethanol, and IPA do), this seems unlikely.
(note: at least methanol and ethanol do also form azeotropes with n-butane, and methanol will form one with propane, though these aren't listed on
wikpedia)
Also, as far as potential ethanol contamination, it is possible for potassium hydroxide (along with the presence of water) to hydrolyze DEE into
ethanol, albeit slowly at ambient temps and slower at lower temps. But this might be enough to form trace amounts of ethanol and result in some of the
behavior seen here. On top of that, acetaldehyde is considerably more easily converted to ethanol + potassium acetate when exposed to potassium
hydroxide.
Given 85% KOH was also mentioned, this would likely have significant potassium carbonate contamination as commercial KOH tends to have, so that might
also be a consideration. (though I believe potassium carbonate would generally be less reactive, less prone to forming acetate from acetaldehyde and
unlikely to form potassium ethoxide, so it probably wouldn't be an issue)
Though on that note, dry potassium carbonate may be a better option for drying DEE and precipitating any peroxides that form, as well as removing
water present, without the same reactivity potential as KOH. (including reactivity with acetaldehyde)
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bnull
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Quote: Originally posted by pots-o-potash  | | Also, as far as potential ethanol contamination, it is possible for potassium hydroxide (along with the presence of water) to hydrolyze DEE into
ethanol, albeit slowly at ambient temps and slower at lower temps. |
Are you sure? I didn't find anything on alkaline hydrolysis of diethyl ether. [1], for example, has nothing on this. To be honest, there was one
instance of alkaline hydrolysis, but it was of an aromatic ether at 200 °C or so, which is not the case.
I'd go with the interaction of acetaldehyde condensation products with ether in the presence of base.
[1] Robert L. Burwell Jr., The Cleavage of Ethers, Chem. Revs. 54, 615-685 (1954).
Quod scripsi, scripsi.
B. N. Ull
P.S.: Did you know that we have a Library?
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