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Acid Scavenger
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Distilling it would be a very easy step to skip over. You are SO close, why stop now?
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MrHomeScientist
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Thanks Magpie, those are both easy methods that I should have thought of! I have both of those reagents. I think CaC2 will
be the way to go, since I'd have to dehydrate my copper sulfate first.
As for distilling, I suppose there's no reason not to. It's just a bit of a hassle to set up the apparatus, water pump, etc.
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blogfast25
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MrHS:
I'm not speaking from experience here but I think only substantial amounts of water in IPA would give those 'positives' (although for 5 % and over it
should work). But conventional drying methods like salting, drying over anh. MgSO4 (Epsom salt) and distillation, should give very low water contents
in your end product.
[Edited on 29-3-2014 by blogfast25]
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S.C. Wack
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No ones saying anything really about a water pump...what's the solubility of NaOH in IPA? You may be in a position to tell us...
Is there a known factual basis for the usual recommendations of drying with sodium and magnesium sulfates? I guess it depends on the definition of
dry...they seem to be mentioned mostly due to the non-reactivity, but it would be interesting to compare with calcium sulfate.
[Edited on 29-3-2014 by S.C. Wack]
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blogfast25
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S.C.:
Good point. Most of use would dry IPA with the methods discussed here and take a BP. If it's close enough to the tabled value, most would be happy
with that. But truly anhydrous IPA may be a much more difficult thing to achieve. And once below a certain level you'll need Karl Fisher (or maybe
some GC?) to measure it.
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forgottenpassword
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IPA forms an azeotrope with water so you can dry it further by boiling off a small amount sufficient to carry away the residual water.
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MrHomeScientist
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Quote: Originally posted by S.C. Wack  |
No ones saying anything really about a water pump...what's the solubility of NaOH in IPA? You may be in a position to tell us...
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Water pump for the condenser, as in to condense the low-boiling vapors of isopropanol.
As for solubility I don't know. I suppose I'd need to take my "dry" IPA, stir in NaOH prills, and decant, dry, and weigh the remainder. The fact that
it's so hygroscopic would complicate measurements, though.
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Magpie
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| Quote: Originally posted by blogfast25 | ...
I'm not speaking from experience here but I think only substantial amounts of water in IPA would give those 'positives' (although for 5 % and over it
should work)....
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You may well be right here. The context of my lab manual was a comparison of the results for 95% ethanol and absolute ethanol.
I prepare absolute ethanol by using 3A mole sieves on 95% ethanol. The product is good enough for Grignards.
The single most important condition for a successful synthesis is good mixing - Nicodem
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vmelkon
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| Quote: Originally posted by Magpie | | 2. Place 1 mL of your dried IPA in a small test tube. Add a little CaC2 (calcium carbide). If you see tiny bubbles of H2 then that indicates the
presence of water. |
What reaction takes place to produce H2?
Perhaps you means acetylene (ethyne) is produced as the CaC2 reacts with the water and you also get Ca(OH)2.
Signature ==== Is this my youtube page? https://www.youtube.com/watch?v=tA5PYtul5aU
We must attach the electrodes of knowledge to the nipples of ignorance and give a few good jolts.
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S.C. Wack
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If you distill your IPA, you'll get a good guess. Aha! on the water pump...I think nothing of it to the point where my fountain pump is in its bowl in
yucky half-evaporated water pretty much 24/7 including right now. It shouldn't be a big deal to hook up if you use surgical tubing.
CuSO4 bluing would be easy enough to test with HEET/isoheet/$60.30 per liter Sigma IPA, and drops of water.
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Magpie
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| Quote: Originally posted by vmelkon |
What reaction takes place to produce H2?
Perhaps you means acetylene (ethyne) is produced as the CaC2 reacts with the water and you also get Ca(OH)2. |
Yes, I meant acetylene.
The single most important condition for a successful synthesis is good mixing - Nicodem
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blogfast25
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Magpie:
In my experience commercial CaC2 is fairly sluggish, even with pure water (it is after all a hard calcined product). Small amounts of water in an
inert matrix will further reduce reactivity. In short: it may take quite some time before any acetylene bubbles form.
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nimgoldman
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Sorry for bumping the thread, I wanted to clarify how much salt is actually needed...
Assume 1 000 g of 50 wt% IPA, that is 500 g IPA + 500 g water.
Of the 500 g water, I calculated about 70 g should go into azeotrope as we cannot salt beyond that. The azeotrope is: 70 g water + 500 g IPA as this
gives the composition: 87.7% IPA : 12% water.
The remaining 430 g of water would contain about 150 g NaCl (saturated brine).
From this it seems only about 150 g NaCl is needed to salt out a kilogram of 50% IPA.
This seems acceptable as removing the bulk of water saves us from extremely time and energy-consuming fractional distillation...
I would still distill after drying IPA, but the pre-drying with NaCl seems to greatly speed up the process.
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Fery
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The water/NaCl phase still contains some amount of IPA. When having larger volumes, it is worth of distilling the IPA even from water phase. I
processed 5 L of 70% IPA and distillation of the bottom brine layer boosted the yield by 20%.
https://www.sciencemadness.org/whisper/viewthread.php?tid=14...
Using only NaCl for salting out, I achieved density 0,829 g/ml = 85,5 wt %.
I did not dry it further using NaOH to anhydrous IPA.
I used 1 kg of NaCl for that experiment, which was sufficiently enough, not the all NaCl dissolved, but it is better to have some excess of NaCl.
Also the upper IPA layer contained some NaCl (which revealed as a distillation residue) - very likely caused by the H2O present.
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