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angelhair
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Can anybody confirm the efficency of Sodium carbonate and whether there are any condensation products?
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Klute
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I routinely use K2CO3 for drying and distilling acetone with good results. Anhydrous Na2CO3 should do th ejob well enough, although you might want to
leave it a bit longer as it is less effective than K2CO3.
But i think the quality of the acetone required for most basic reactions is over estimated. A simple distn is more than enough in most cases. Keeping
the acetone dry is more important than getting those last 0.5% water out IMHO.
\"You can battle with a demon, you can embrace a demon; what the hell can you do with a fucking spiritual computer?\"
-Alice Parr
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panziandi
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Indeed, for most purposes I just use aceone LR or BP grade fresh from the bottle and quickly replace the lid. If it specifies a very dry product
shaking with some anhydrous K2CO3 is best, decant and distil into a flask closed to the atmosphere with a CaCl2 drying tube.
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Panache
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I might try some partially wetted acetone at -85 to see if the water freezes out. absolutely nothing is happening with ether
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panziandi
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That is a completely pointless post. Not everyone is a meth cook and this is not the home of meth cooks. This thread started as a question to clarify
what was meant by "dry" in terms of solvents (specifically acetone). Dry acetone is very useful, e.g. for reacting with organo-metallics, wittigs the
list is almost endless for moisture-sensitive reactions. Not to mention as a means to isolate hygroscopic amine HCls, not meth. Like this forum is
about sciencemadness... not science that causes people to go mad and write gibberish nonsense on the threads.
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Panache
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i am surprised it was so well punctuated and spelled, i guess all the effort went into that, as opposed to the content.
I would like to tell Scienemadness members i believe acetone vapours are not directly harmful in small amounts and they should not worry about their
health should they smell acetone. Its not HCN, to be avoided at all costs, and worrying about acetone vapours whilst making/taking drugs in a kitchen
is similar to worrying about contracting SARS from the ambulance you have called to treat your life threatening burns from the kitchen fire after you
stumbled carrying a casserole dish of boiling flammables whilst smoking.
And who are these 'real ppl' who apparently only dry ether not acetone. I am a real person, i think, and i dry acetone, Klute i think is a real
person, he dries acetone apparently. I think i'll need greater proof of these real people before i stop drying my acetone.
That said in relation to my earlier post on drying solvents by subjecting them to -85C for sometime and decanting the solvent from the solid water. I
also tried this with acetone (ether was unsuccessful as far as my experiemnts went). and had similar results. I have however emailed the collator of
that water site i mentioned in Misc asking him about the concept of it, i feel there must a fundamental thermodynamic reason for it to fail rather
than simply a kinetic one and the reason will vary from solvent to solvent depending on its relationship with water. Water is very very very
complicated i have recently learned, did you know presently evidence indicates water gets around as (H2O)280 clusters and these clusters, highly
organised, are constructed from units comprising of four, bicyclo octomers of the molecule we refer to as H2O, these octomers are the crystal form of
ice7 of of the 17 crystal structures of crystalline ice, there are also 6 amorphous ices, of which ordinary ice is one, (all the crystalline varieties
have below parity density) and common amorphous ice, compared with liquid water, has a 100fold poorer capacity to resonant with the microwave
radiation typical of the kitchen microwave, explaining why defrosting in the microwave sucks so bad!!
Anyway will update if the dude gets back to me.
[Edited on 28-9-2008 by Panache]
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vulture
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Will you people get back to the topic at hand or kindly STFU. Panache, your nonsense is getting irritating. Cut it out or be cut out from the board,
your call.
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angelhair
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How hygroscopic is dry acetone?
If you used K2CO3 to dry it and then left the acetone in an open beaker for a few hours would it soak up enough water to call it reasonably wet?
[Edited on 15-10-2008 by angelhair]
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jarynth
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After a few hours in an open beaker I would call it reasonably gaseous.
Besides, I wouldn't use bases to dry ketones. But if you only have K2CO3, you can make a better drying agent (for alcohols etc) by roasting it. You
will also get some decomposition to KOH.
[Edited on 15-10-2008 by jarynth]
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Klute
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K2CO3 is perfectly suiatble for drying ketones. Just read "Purification of Laboratory Chemicals". It is even prefred to Na2SO4 or MgSO4 as it causes
less aldol condensation.
I don't understand what you mean by a "bbetr drying agent". Anhydrous K2CO3 in anhydrous K2CO3. heating it in an oven isn't going to change much,
unless it is already partially hydrated. But it is assumed the anhydrous salt is used. KOH, even in traces, is going to be very bad for acetone and
ketones.
Drying acetone and leaving it in the open air for a few hours is a bit pointless. Better just dry it and keep it in a closed bottle, or at least in a
covered beaker. It will absorb some water, depending on your ambient humidity, but not as much as say absolute ethanol. Depending on the quality of
the acetone you get in the first place and your needs, you might betetr be off using it directly in that case. Better just dry it correctly, and keep
it as such.
Keeping acetone over K2CO3 isn't a good idea because it is easily suspended and somewhat slow to decant, so you will poor fine K2CO3 with your
acetone when you use it.
\"You can battle with a demon, you can embrace a demon; what the hell can you do with a fucking spiritual computer?\"
-Alice Parr
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jarynth
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| Quote: | Originally posted by Klute
K2CO3 is perfectly suiatble for drying ketones. Just read "Purification of Laboratory Chemicals". It is even prefred to Na2SO4 or MgSO4 as it causes
less aldol condensation.
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Please disregard my post, I didn't read the whole thread. I guess what I was thinking was that K2CO3 is very hygroscopic, so you'd have to dehydrate
it before use.. but this may cause the formation of the oxide (or hydroxide), with all the consequent problems.
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Klute
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Well, in order to be sure the salt is an anhydrous as possible, it always best to dry it at 100°C for a while depending on how you store it, but for
routine drying like this it's genrally not needed.
By the way, I have always found it to be better to add a little Na2SO4 or MgSO4 before adding K2CO3 to a very wet organic, as K2CO3 can form a thick
liquid when in presence of too much water. Adding a little sulfate avoids this, as the K2CO3 clumps arounf the sulfates at first, then get free as it
absorbs the water correctly. I have always found K2CO3 much more quick and effective than the sulfates. Hope it cna help.
\"You can battle with a demon, you can embrace a demon; what the hell can you do with a fucking spiritual computer?\"
-Alice Parr
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Panache
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| Quote: | Originally posted by jarynth
After a few hours in an open beaker I would call it reasonably gaseous.
Besides, I wouldn't use bases to dry ketones. But if you only have K2CO3, you can make a better drying agent (for alcohols etc) by roasting it. You
will also get some decomposition to KOH.
[Edited on 15-10-2008 by jarynth] |
So k2CO3 will go to KOH with heat, will it completely convert. KOH is always annoying in melbourne i have found, its either the high prices of the
chem suppliers or the inconvenience of a solution. i will check vogel firstly, sry thinking out aloud.
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jarynth
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Well, after roasting the carbonate (small prills, about 300 microns) for a while I got a light powder that reacted noisily upon solution in water with
the generation of heat, much like NaOH does, but not as vigorously.
I did weigh reagent and product but, not knowing the exact degree of hydration of the carbonate, I wasn't able to compute with certainty the molecular
mass of the product. I suspect I got a mixture containing K2CO3, K2O, KOH, KO2, etc.
Can't you make the hydroxide by the reaction of the carbonate with Ca(OH)2? Or by heating the sulfite, bisulfite... followed by quenching in water?
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blogfast25
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Here's a bit of a conundrum for all you 'pro acetone driers': my acetone after use (drying ZrOCl2.8 H2O crystals) contains water, FeCl3 and some...
HCl! I could just dump it but not having much to begin with I'd like to recycle as much as possible.
Having overlooked the HCl, you can imagine what happened on addition of anh. Na2CO3! To stop the foaming (the smell of acetone became very strong) I
had no choice but to add some NaOH, ending up with a bottom of mainly NaCl, NaOH, Fe2O3. I cautiously distilled (after filtering, of course) it and it
came over at 57.4 C.
There must be a better way though to get shot of the HCl...
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not_important
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Pretreat with CaCO3, even gardening limestone. Add just a little and stir for awhile, then add a little more and repeat until bubbling stops. Let it
settle, if there was a lot of HCl then there may be some concentrated CaCl2 solution making the excess CaCO3 pasty, no harm; the iron will colour the
excess carbonate s\as it falls out of solution. Decant through a filter and then dry the filtrate with soda ash or K2CO3.
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blogfast25
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Good idea!  But what would be wrong in adding quite a lot of CaCO3 (say
10 g/100 mL of acetone?) in one go, perhaps in a wide bottomed flask (thus improving contact), decanting/filtering off and then adding the drying
agent? I've got just the kind of limestone for it, quite a 'pure' variety...
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not_important
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Plop plop fizz fizz ...
keep the fizzing and foaming down by starting off with a small amount. Note that crushed limestone is courser and should react slower, and may be OK
to just dump in. Marble or limestone bits are used to neutralise the HBr/HCl from brominating/chlorinating acetone or other simple ketones, it's not
reactive enough as a base to give bothersome condensations (but the hydrogen halide is acid enough to cause problems)
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blogfast25
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Marble is exactly what I've got, nice little pebbles of just the right reactivity...
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bbartlog
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Quote: Originally posted by not_important  | Pretreat with CaCO3, even gardening limestone. Add just a little and stir for awhile, then add a little more and repeat until bubbling stops. Let it
settle, if there was a lot of HCl then there may be some concentrated CaCl2 solution making the excess CaCO3 pasty, no harm; the iron will colour the
excess carbonate s\as it falls out of solution. Decant through a filter and then dry the filtrate with soda ash or K2CO3.
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I think I would distill just because acetone forms condensation products when exposed to HCl, even at room temperature. Maybe if there wasn't a lot of
HCl and it hadn't been sitting long?
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blogfast25
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Oh but yes: the recycles acetone will be redistilled, if only to get rid of some residual salts/solids.
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blogfast25
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Well, well, well, the first attempt at drying acetone previously used to dry and extract small amounts of FeCl3 from ZrOCl2.8 H2O is yielding an
interesting result.
I added a few marble size pieces of actual marble to about 400 - 500 mL of used acetone, to eliminate HCl. Bubbling started right away: not vigorously
but noticably and steady nonetheless. That was last night.
Today about 18 h later and the system has developed in a two phase liquid/liquid system, with lighter coloured opaque and heavier liquid sitting
underneath a pale yellow opaque phase. It's a true two phaser: shaking up the bottle briefly disperses the phases but they separate back very quickly.
Water and acetone are supposed to be miscible in all ratios.
Marble and HCl of course form CaCl2, water and CO2. Is it possible the formed CaCl2 is a solubility suppressant for acetone in water? I'll test this
idea independently...
Assuming the heavier phase is watery then it's probably quite rich in CaCl2 by now...
[Edited on 3-7-2010 by blogfast25]
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blogfast25
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I separated the small heavier fraction (w/o attempt at analysis - lack of time). The supernatant liquid was perfectly clear and pale yellow (due to
the Fe3+). I added a small amount of 'bottom' fraction (BP = 88 C) from a previous nail polish distillation and some more bubbles appeared: Ca(HCO3)2
reacting with some acidity in the 'bottom'? I added the marble again and got some more CO2 for about 10 mins, at the end of which the liquid had
turned an amber - reddish colour, presumably due to hydrolysis of Fe.nH2O(3+)..
The marble removed, 20 g of anh. Na2CO3 was then added and shaken regularly, no CO2 eluted. After a couple of hours the liquid had cleared up
completely with hydrated ferric oxide at the bottom and the Na2CO3 solidified completely. It was left standing overnight. After filtering the BP was
established at about 62 C and the 400 (or so) ml distilled off at about 57.5 C.
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