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peach
Bon Vivant
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I realize it's very easy to spot AlCl3 once it's isolated in it's natural habitat and in the metaphorical headlights, but that neoprene entirely
ruined what appeared to be working very well. No simple way to separate the AlCl3 from the unreacted aluminium sprang to mind, so I was attempting to
push it forward to completion, to get said sample for testing. I also felt comfortable I could achieve that after seeing it effervescing as it did.
I purposefully stopped gassing and left it to finish effervescing on it's own. When I came back to finish it, I thought "Oky doky, I'll give it a try
in one of my newly arrived, better sized flasks". That meant extending the down tube, as the flask wasn't better sized in this sense; only in it's
volume. Based on how I'd seen the neoprene behave with the components separate from each other, I assumed (remembering what assumptions make you and
me) it'd probably be okay to dip a bit into the solution. Wrong, wrong, wrong, I will certainly admit that critical failure, although, it was an error
based on some degree of reasoning.
I don't just suspect the neoprene, I am confident it was that specific contact that ruined the attempt to finish the material. I was so genuinely
concerned about the foul smelling, unpredicted gas that resulted with the neoprene in contact, I wasn't in anyway going to attempt carrying on with
it. If not for that, for the fact it was now becoming obvious the tubing had caused some significant deviation from what should have been happening,
and so the product I was testing would also be heavily contaminated.
As much as I go on about fume hoods being overused and safety being taken out of perspective, this is one of the few examples were I would have liked
one to store the flask in whilst it gassed. As I've also said, the reason for that is not the HCl(g) (which I can easily deal with outside of a hood,
using very little effort) but that the neoprene result went totally out of control in terms of knowing what the fumes were (with
plastics and rubbers emitting some of the most disgustingly carcinogenic materials known to man as they degrade). As I had no idea what was coming
off, I also had no way to safely scrub it, or assess it's risk potential, so assumed (this time for the better I expect) to 'run away'.
There was most definitely something in there that was violently reacting with water. On trying to rinse the flask out, there was a gigantic volume of
persistent fuming and heating, which went on for hours.
But yes, in need of an all glass, tygon run it is. I am still watching this thread and working on this. It's just taking a while for me to piece
everything together; I want to make sure it either fully confirms or strikes off the idea. I'm very busy working on some other things, so it's a kind
of side project that's coming together bit by bit as things turn up in the post.
Once I have the glass and bits I feel happy with, I'll certainly rerun it and post up the results, whether it functions or fails. I'll make a video
for you, I'm finding it's by far the quickest, easiest and most detailed way to record and convey information.
JOHN 
[edit]I'm not sure what you mean by the dark stuff. You mean in the videos? That 'dark' muck will be the unreacted aluminium sat at the bottom (I was
switching the stir bar off so you could see it churning it's self). The fluffy stuff floating around like little flocculated puffs of fluff will be
the acid, if it's functioning. If you mean in the photos, I have no idea about that either. I have asked here before about it, and not got an answer.
It's supplier supplied CP AlCl3, it's production had nothing to do with me. The dark colour of the solvent is only me rinsing it back off (which took
ages, a lot of effort, and entirely seized a taper, beyond repair). That's part of the reason for me wanting to make the acid myself.
I feel relatively sure I can do a lot better than the commercial material I bought, and that pure white precipitate in the all glass run hints that
this may be true. I also don't like the big nodules the supplier's AlCl3 comes in, they basically don't stir, and jam up the bar, even in a lot of DCM
(which an equal 'a lot' of people expect it'll dissolve fine in).
[Edited on 13-8-2010 by peach]
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Magpie
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I'd be careful which Tygon tubing I selected. The stuff you get at the hardware (DIY) store may be loaded with leachable plasticizers.
http://www.tygon.com/tygon-traditional-tubing.aspx
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peach
Bon Vivant
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Carrrr, carrrr, jack jack jack jack...
Warning is accepted, as I know numerous people are using standard tygon and wondering why it's going wonky.
However, as I say, this is the latest addition to their ultra-chemically resistant line.
Click the link to this PDF on the Saint site and have a peruse of the relative chemical resistance table on the right, just below the one at the
top
The 2375 is supposedly even better than this.
As I also say, I've actually spent a long time looking at the even more resistant options, like pure PFA, FEP and PTFE. But, whilst they're slightly
better in terms of ultimate resistance, they're mechanical properties also make them a pain in the ass to work with in terms of connecting to bits of
glass that needs taking apart, cleaning, setting back up in different patterns and so on; they're too rigid (so they'll tend to try and pull glass
over or put strain on it), usually opaque (can't easily see if there's a condensation problem developing) and don't stretch or flex very much (meaning
they can't be forced over gas ports, won't seal very well and will tend to slip off). They're good for things like HPLC, but that's because the
equipment is in a pretty much permanent setup, weighs a ton and has specialized fittings to grip the tubing.
All this makes the ultra-chemically resistant tygon the best option I can think of in terms of laboratory glass. It's not as truely inert as the true
fluoropolymers, but it's very close. And it's far more suited to draping and push fit connections. Added bonus, it's smooth as glass inside (making it
very easy to clean, important) and it's crystal clear (so it's easy to see what's going on inside).
It's also why I have that pricey PTFE thickened vacuum grease. When a single experiment like this is using up pages of people debating every detail
and waiting for one or two people to report back, I can do without the tubing / grease variable, thank you thank you.
I'm having a chat with the girlies at Saint about 2375. I'll report back on how it performs. If any of you are interested and thinking of doing some
corrosive / reactive gas work, shoot me a PM just to say (yep). If I get enough PMs showing some interest, I may buy a big spool in a size and grade I
know will work and chop it to order up for yars. The typical spool lengths are far too long and far too expensive for amateurs on a budget; you just
need to think about what lengths you're going to use prior to firing up the scissors and binning it after one go.
"CARRR, that jumper's almost shiny, I'll take that as well!"
[Edited on 13-8-2010 by peach]
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blogfast25
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'Black stuff': I'm referring to your second photo of a conical flask on page 3, with a dark liquid at the bottom, erm... 'John'.
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blogfast25
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My best bet regarding the whitish material you claim is anh. AlCl3, is that it is in fact a mixture of Al hydroxy chlorides (Al(OH)nCl3-n) and
possibly some plain old hydrated alumina. I think water has gotten into your system, causing the reaction by the usual means: 3 H3O+ + Al + n H2O
---> Al(H2O)n 3+ + 3/2 H2 + 3 H2O. Any AlCl3 formed would be partially or wholly hydrolysed.
I'd bet your product would not sublime and would not work as a Friedel Crafts catalyst.
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DJF90
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Well I'd bet that in order for you to be correct, Blogfast, that there would have to be a shit-load of water kicking about. We're talking saturated
DCM, moist aluminium powder and wet HCl gas stream. Now I don't know about you, but peach doesn't appear to be that sloppy of an experimenter. Just
what's the problem with him actually making anhydrous AlCl3? Its hardly impossible, and in my personal opinion, I believe he's done just that. Until
he runs it again sans neoprene, and has obtained some concrete results with analysis, lets give the lad a break - he's obviously making good progress
and I'd hate for the negative comments from someone like yourself to put him off trying it again, or even worse, prevent him from posting the results
here when he does finally get it working ok.
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peach
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Quote: Originally posted by blogfast25  | | 'Black stuff': I'm referring to your second photo of a conical flask on page 3, with a dark liquid at the bottom, erm... 'John'.
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erm... 'blogfast', as I've now explained, at least twice, that 'black stuff' is from commercial grade, supplier bought AlCl3. Not a product of this
reaction. Indeed, I stated this (I believe) on the first page, with similar photos, whilst I was explaining why I was trying to run this method.
Are you actually reading prior to hitting reply?
I've supplied written evidence, photos and now videos, and you're still repeating the same questions.
I'm perfectly willing to be wrong, and for you to be right, but I've explained the dark solvent now a few times. How many more times do I need to
repeat this? What's this? The third time?
[Edited on 13-8-2010 by peach]
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entropy51
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| Quote: Originally posted by peach | I've supplied written evidence, photos and now videos, and you're still repeating the same questions.
I'm perfectly willing to be wrong, and for you to be right, but I've explained the dark solvent now a few times. How many more times do I need to
repeat this? What's this? The third time? |
Where is the "evidence" that you've made any AlCl3
whatsoever? At least you got the thread title correct: "Preparation of anhydrous AlCl3 in DCM - photos". There are photos and lots of chit
chat, but nothing to show that your mystery gunk is AlCl3. Instead of personally attacking me for "complaining", why don't you cough up your alleged
"evidence" that the emperor is indeed clothed.
Better to remain silent and appear a fool than to open your mouth and remove all doubt.
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peach
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There is indeed a lot of chit chat, however, I'm sure you'll agree a lot of it is either coming from pure speculation (as opposed to me having
actually tried it, written it down, taken photos and made a video; albeit, without a test of the result video as of yet).
We have people who aren't sure about the solubility of it in DCM telling me it probably hasn't worked because the product would go into the solvent.
Fairly basic stuff to be making comments on the reaction.
I've made it quite clear I'll be using ultra-chemically resistant tygon in the future, but have been told to be careful which tygon I choose. I'd
expect you to make some comment about this being pointless, then demand I use it if the result functions. So I'll go with the 'pointless' chemical
inertness in anticipation of any complaints should the result function.
I've posted evidence all over this thread showing that aluminium does react, in some way, with what appears to be aluminium, DCM and HCl(g) alone in
an all glass setup. That is somewhat speculative evidence, agreed. Throwing a pure white crystalline result into some water and watching for fuming is
less so, but I'm sure someone could still find room to argue about that result as well.
The 'evidence' I'm referring to in response to blogfast is the commercial grade material being impure and not part of this reaction; the photos (which
I've now posted twice, with explanations of what it is and what I'm doing to it).
| Quote: | | I'm perfectly willing to be wrong, and for you to be right, but I've explained the dark solvent now a few times. How many more times do I need to
repeat this? What's this? The third time? |
And, in effect, you are still complaining. I know a pure white, material that violently fumes hasn't been shown yet, I've only mentioned the odd
fuming when washing the glass out. A number of other people have already commented on that not being a solid result yet, which I've acknowledged and
replied to with the following;
| Quote: | I've now spent £ha£hing on a few wash bottles specifically with the intent of redoing this all in glass to a full conversion to the white
precipitate, but I'm still trying to collect a few other sizes so I don't have to run it in this monster. For a size comparison, there's a tiny
tomatoe, a slightly bigger tomatoe, a large tomatoe, a jar of beetroot, a 250ml wash bottle, the 500ml wash bottle, a 2l bottle of Vimto concentrate.
Note that the down tube still doesn't get very close to the base, so I'll need some more borosilicate on the end and a frit. I'm starting to feel like
Dr Evil getting this sorted...
"You know, I have one simple request. And that is to have sharks with frickin' laser beams attached to their heads! Now evidently my cycloptic
colleague informs me that that cannot be done. Ah, would you remind me what I pay you people for, honestly? Throw me a bone here!"
I have some Tygon 2375 in the post, which is Saint's updated version of their 2075 Ultra-chemically resistant tubing (doesn't even seem to be listed
on their site yet). Unless someone wants to paypal me funding for PTFE (which also requires special fittings) and other more high end bits and pieces,
that's the best you're getting. |
It's fairly obvious I am actually reading the replies (as evidenced by the massive one on page 3, replying to all the questions about things like
solubility, with first hand experience of these properties, and why someone might want to do this).
In essence, you're moaning about repetitive observations that are already being taken into account, again. And, again, this is something you'll have a
go at other people for when they 'state the obvious' in threads you're taking part in.
Look, I get the point. It's been made a lot of times already, I haven't made any solid claim as to having produced it since people asked for an all
glass style run, I've actively told others what they have may not be anhydrous and I'm spending money and time getting the bits together so the other
people in this thread will know for sure if it does or doesn't work; for free. I'm not a millionaire, it will take a little while to get a result with
a very low degree of potential error.
[Edited on 14-8-2010 by peach]
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blogfast25
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John,
You don't seem to understand. The difference between anhydrous AlCl3, a very useful product, and slightly moist goo (a mixture of Al(OH)n Cl3-n.m H2O
and Al(OH)3.k H2O) is HUGE.
Try and repeat the experiment with just one (1!) drop of water added to the DCM: reaction will be slow, yet decisive. The water will act like the
catalyst you need to chlorinate Al with HCl, except it will also hydrolyse the product.
Your experiment took place over quite a long duration, even with quite dry reagents you're probably accumulating water.
The reaction between Al and HCl at RT in the presence of an inert 'solvent' is simply something that according to the known Laws of the universe isn't
possible.
The onus is on you to provide unequivocal proof of the miracle: dry AlCl3. Until further notice some of us will keep betting on those safe Laws of the
universe...
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peach
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You're explaining the properties of Lewis acids to someone who has spent years working with them, more often they than B/Ls.
I know the difference between hydrate and anhydrous.
One drop of water will not hydrolyze a batch of Lewis acid. One drop equates to 0.05ml, which is roughly 0.05g, which is roughly
0.0028 moles of H2O. I'm dealing with tens to a hundred grams of hard Lewis acid on a regular basis. That's a 26 molar excess, minimum.
Maybe I've misread what you're saying, but the water can not catalytically hydrolyze Lewis acid in that fashion, for the simple reason that there's
nowhere else for the hydrogen to come from to produce the resulting hydrogen chloride fumes, but additional water.
Where in this seemingly catalytic hydrolysis you propose is the HCl(g) getting it's hydrogen from other than the water? How does more than an order of
magnitude less water hydrolyze that quantity of acid? Why do the workups involving Lewis acids hydrolyze their reaction with at least an equimolar
amount of water to acid? Why does my flask cease fuming when left, yet fume in a linear fashion as I add water?
As more water contaminates the sample, it degrades the Lewis acid acids proportionally and, perhaps more importantly, yields B/L acids that do then
cause the acid to behave in different fashions. E.g. Lewis acids on their own (as I understand it from a post by Sauron or Nicodem) have a hard time
demethylating toluene, and require a B/L present to function. Indicating a partially hydrolysed Lewis acid will not only skew the yields, but also
allow for side reactions.
The onus is not solely on me to provide evidence for everyone else, until I start claiming it as fact. I'm simply providing the evidence as I get it
myself, making judgments on that and asking reasonable questions about what it could be if it's not yet the acid.
And now, for the billionth time, yes... I will be re-running it, I have not only hinted at that, but described in detail (which seems to be surpassing
a few of you) how I'm going to do it. And I will be posting results whether it's successful or fails.
I was purposefully not replying to this thread to avoid speculation that goes beyond what's available. But, some of the replies are so blatantly
incorrect they don't require any further testing (e.g. AlCl3 dissolves in DCM, so the results seen so far can't be AlCl3). I don't mind people making
mistakes, or want to pick away at them and call them idiots, but that is simply wrong and needs stating very clearly as such; and I've posted the
photos of why that is so, twice, with explanations, which you yourself seem to have overlooked (e.g. "solvent is dark brown", suggesting you thought
that was a product of the reaction).
Your own reply, regarding one drop of water ruining the entirety of the Lewis acid sites, is equally incorrect. If it were not, hard Lewis acids would
come in sure-seal bottles. They don't. Also, see the above questions, which are rhetorical in my opinion.
I'm not trying to argue for the sake of it, or prove I'm 100% correct based on some agreeably shaky results in an unfinished flask. I do 100% agree
that you're correct, this does need rerunning and needs to produce solid acid that fumes at the end. But what I am demonstrating is that the aluminium
is reacting with the gas in a system that is significantly cleaner and drier than anyone else in this thread has so far attempted.
This reply is not so much speculation over the reaction it's self, as what I know to be correct for Lewis acids. Which needs stating so others can see
why my reasoning does or doesn't function.
To throw some speculative questions into the pot, I also routinely form anhydrous AlI3 at low temperatures using I2, the same aluminium source,
solvents and same methods (or worse) and yield a result that not only fumes on contact with the atmosphere, but also functions in the subsequent
reactions, and shows it's doing so on TLC plates. I2 alone will react with aluminium if left to sit for a few minutes at room temperature.
Let this be the last time I have to say this, should anyone else say it needs repeating, it will be, and you will hear the results! If the thread is
quiet for a week or three, that's me waiting for the post to arrive, compiling videos and uploading things.
[Edited on 14-8-2010 by peach]
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peach
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Okay! Finally!
I decided to try running it with the 500ml wash bottle, since the others still haven't shown up.
It's all 2375 and krytoxed.
I piranha'd the glass, rinsed multiple times, then baked the entire lot dry in the oven (the aluminium was already in there as well, under nitrogen).
Redistilled the DCM from sodium sulphate and ran the result directly into the still capped wash bottle. Flushed it all through with dry nitrogen, then
generated the HCl from sulphuric on anhydrous, supplier bottled CaCl2. The exit on the wash bottle was going through 98% sulphuric, and continually
flowing in the exit direction.
There were lots of observations I could talk about;
Strong effervescence, observations on the pH of the exhaust gas with regards to addition rates and progress, that the exhaust was ignitable, that
samples of the material in there appear to strongly interact (violently so) with water
Suffice it to say, I'm not happy with this attempt and will give it another go once I have restocked on some other bits.
I suspect, water has made it into that somewhere and produced something ominously like a gel; albeit one that rapidly settles.
I haven't opened the flask yet to have a test of what's in there, but I suspect this ones a gonner, having put molar excesses of HCl through it and
still not having a pure white material.
I had some teething problems running this. For a start, something solid clogged the wash head, twice. Meaning I had to open it and quickly poke the
solid back out (allowing for possible water absorption, despite me doing it in a few seconds). And it was a true solid pellet, not a gel (violent
poking only dislodged it, as opposed to breaking it up).
More of an annoyance, I was using a brand new addition funnel and, later into the night, I could hear a high pitch whine, like a mosquito. I assumed
one of the tapers had opened and spent ten or fifteen minutes with my ear against the glass, pressing on fittings to find the problem.
To my surprise, I then discovered an absolutely minute pinhole in one of the seams of the funnel. By that, I mean I can't actually
see it now with me looking for it. But it's there, because I could see HCl escaping and moisture collecting around the point, and hear it. The HCl was
still leaving this hole, but it's another point of entry and variable.
I now have a replacement funnel in the post.
What I find curious is the end colour of the solvent. It certainly isn't green anymore, it's orangey brown. I have checked the aluminium, it doesn't
appear to be contaminated with iron. Is that the gas generators sulphuric passing into the wash bottle?
I noted the reappearance of that odd smell, despite the change in tubing and use of an all glass setup. Sulphorous material being generated by
sulphuric contamination?
I have a stockpile of dead batteries to hand, so may give Cl2 a go after this since someone asked. Failing that, I have clean Iodine and HgCl2 and
could have a go at priming the aluminium. Neither of these are ideal given the extra complications they involve, but would still be good in terms of
generating a fine, clean result (as opposed to the CP mucky nodules).
I will have to assume the solvent is still too damp and the stream needs further work. I've not had any gel issues preparing AlI3 with these
containers of solvent and poorer methodology. The only thing changing has been the halogen source. Indicating the gas stream may be at fault, if water
has been the problem here.
I could dry the solvent with Calcium hydride, but my supplier doesn't have any. Or molecular sieves.
My current guess is, the sulphuric is damp and needs redistilling. Next time, I will condense it off directly into the addition funnel, then crimp off
the tubing (need some of those crimpy things surgeons use really).
With regards to watson's point, again, I haven't checked the solvent yet, but some solvent (about 5-10ml) did make an attempt to leave the bottle and
puddled in the exit. I was feeling quite tired after being sat there and developed a headache, so was left wondering if perhaps there may have been
(even if they were only traces), some of his chloroform present.
[Edited on 20-8-2010 by peach]
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blogfast25
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CaCl2 is not a brilliant desiccant. I wouldn't trust it for your purposes. Water being the one thing that will lead to misleading results...
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watson.fawkes
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| Quote: Originally posted by peach | [...] generated the HCl from sulphuric on anhydrous, supplier bottled CaCl2. The exit on the wash bottle was going through 98% sulphuric, and
continually flowing in the exit direction.
[...]
What I find curious is the end colour of the solvent. It certainly isn't green anymore, it's orangey brown. I have checked the aluminium, it doesn't
appear to be contaminated with iron. Is that the gas generators sulphuric passing into the wash bottle? |
Armarego 5th ed. on purification of hydrogen chloride, p 430: | Quote: | | Passed through conc H2SO4, then over activated charcoal and silica gel. |
My guess is that your HCl is wet.
The generator you're using doesn't have adequate H2SO4 in it at all times to dry the gas. I don't know the exact cut-over point, but at some point the
residual H2O in the H2SO4 of your generator is going to start preferentially attaching itself to the HCl rather than that the H2SO4. Per Armarego,
concentrated H2SO4 will happily absorb residual water vapor, but that's as part of gas washing train. Silica gel will adsorb any remaining. I'm not
sure how much you need silica gel for a test run, though.
The other possibility is adsorbed water on the aluminum. You mentioned that you baked it, but it's possible that it wasn't long enough. With finely
divided powder, you've got to get all the water vapor out through gas diffusion, so it will bake out faster on a flat sheet than as a compact volume
inside a flask.
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peach
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Thanks for the quick replies watson and blogfast.
The CaCl2 was for the HCl generation, I was using sulphuric to keep water out at the exhaust side.
I used the supplier bottle of anhydrous CaCl2 over table salt to get more gas per unit volume of salt and avoid introducing moisture by using damp
kitchen salt.
Calcium hydride seems to be the preferred method of drying DCM. I'm not sure the DCM being damp is the issue however. I suspect it's that sulphuric.
And the end colour and smell of the solvent suggests the sulphuric may have wandered into the wash bottle.
Edit: Thanks for those quotes, I'll look into trying it as per the suggestion. I too suspect the HCl is damp. £140 for a 220g lecture bottle of HCl,
plus £500 for the monel regulator, plus a university VAT code. Generators are the only option at present. I have found it a lot cheaper and easier to
get, but I also don't need 5kg of it and still don't have the regulator. I suspected activated carbon may be necessary and have a colour indicating
silica tube, but wouldn't I be better replacing the silica with CaCl2?
Double edit: I was just reading this page, which is already purple on my search results and yet slipped by my memory for the ease of using the sulphuric to hand, but I could also
order some more HCl next time from the supplier. He suggests the gas stream is entirely dry when dripping HCl onto CaCl2. Is that going to be true?
There's a lot of water floating around in there to be potentially picked up by the exiting stream.
[Edited on 20-8-2010 by peach]
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entropy51
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| Quote: Originally posted by peach | | Double edit: I was just reading this page, which is already purple on my search results and yet slipped by my memory for the ease of using the sulphuric to hand, but I could also
order some more HCl next time from the supplier. He suggests the gas stream is entirely dry when dripping HCl onto CaCl2. Is that going to be true?
There's a lot of water floating around in there to be potentially picked up by the exiting stream. |
The
HCl(g) prepared by dripping Conc. HCl onto CaCl2 should be dry enough. I have used that method to prepare AlCl3 the dry way. The paper referenced in
your link has been discussed and posted on this forum.
Your description of your method above sounded as if it should be adequate for removing all but minute traces of H2O. I wonder if there isn't a
problem other than traces of H2O hiding somewhere? I think the purple color of your reaction may be a clue, but I don't know what it means.
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blogfast25
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| Quote: Originally posted by entropy51 | | Quote: Originally posted by peach | | Double edit: I was just reading this page, which is already purple on my search results and yet slipped by my memory for the ease of using the sulphuric to hand, but I could also
order some more HCl next time from the supplier. He suggests the gas stream is entirely dry when dripping HCl onto CaCl2. Is that going to be true?
There's a lot of water floating around in there to be potentially picked up by the exiting stream. |
The
HCl(g) prepared by dripping Conc. HCl onto CaCl2 should be dry enough. I have used that method to prepare AlCl3 the dry way. The paper referenced in
your link has been discussed and posted on this forum.
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Are you referring to the dry and HOT method here, entropy51?
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entropy51
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Yes, the hot dry way. Unfortunately, it may be the only way.
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blogfast25
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Methinks so to. But he seems to be having an honest shot at it.
But HCl from conc. H2SO4 and CaCl2 already dry enough? Perhaps, if you're using a lot of H2SO4, as acid and as desiccant at once, which is what John
seems to intend.
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peach
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| Quote: Originally posted by entropy51 |
Your description of your method above sounded as if it should be adequate for removing all but minute traces of H2O. I wonder if there isn't a
problem other than traces of H2O hiding somewhere? I think the purple color of your reaction may be a clue, but I don't know what it means.
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Thanks, although I suspect blogfast may be on to a problem with that method of generating it.
Dried the solvent as best as I can and redistilled prior to use, porting straight into the wash bottle.
Checked the aluminium for contamination, seems very clean.
Generated AlI3 using this and poorer work no problems.
Looks like it's the generator, as per watson's suggestion.
Not sure what you mean about the purple result, it's orange / brown. There's a piece of white paper and black duct tape that I was using as a colour
reference stuck to the back. I believe the purple you're seeing is the black tape. I still don't know why it'd be such a pronounced orange, given
what's in there.
This needs redoing, with watson's modifications in place. I doubt that hydrochloric onto CaCl2 method is going to be any drier. There is far less
water present in the H2SO4 generator. If the gas is picking moisture up from that, it'll pick it up from the hydrochloric even better.
[Edited on 20-8-2010 by peach]
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blogfast25
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John, is the choice of CaCl2 as anion source for a particular reason? Semi-calcined NaCl might be drier?
[Edited on 20-8-2010 by blogfast25]
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watson.fawkes
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| Quote: Originally posted by peach | | I piranha'd the glass, rinsed multiple times, then baked the entire lot dry in the oven (the aluminium was already in there as well, under nitrogen).
Redistilled the DCM from sodium sulphate and ran the result directly into the still capped wash bottle. Flushed it all through with dry nitrogen, then
generated the HCl from sulphuric on anhydrous, supplier bottled CaCl2. The exit on the wash bottle was going through 98% sulphuric, and continually
flowing in the exit direction. |
I realize I'm unclear about the experimental setup. Is there one wash bottle
(for the Al-in-DCM reaction) or are there two (Al-in-DCM and H2SO4)? Related, I'm unclear on the order of the gas flow. Is it [ generator ->
reaction wash bottle (Al/DCM) -> H2SO4 trap (tube bubbler?) ] or is it [ generator -> H2SO4 trap wash bottle -> reaction wash bottle ]?
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peach
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| Quote: | The CaCl2 was for the HCl generation, I was using sulphuric to keep water out at the exhaust side.
I used the supplier bottle of anhydrous CaCl2 over table salt to get more gas per unit volume of salt and avoid introducing moisture by using damp
kitchen salt. |
That is not some loaded annoyance quote, I'm just using the CaCl2 because it's the driest possible thing I have to hand to produce it.
It's from Prestons, anhydrous and has always been resealed before it was ever put down. My thinking was, it'd be next to moisture free, leaving only
the sulphuric remaining as the possible issue.
Given the colour of the solvent, that can't be the aluminium alone interacting with the DCM (obviously). That's the HCl(g) or sulphuric has come over
in the gas stream.
As Watson suggests, and I suspected, it's going to need activated carbon in the way to stop any sulphuric contaminants coming over.
Generator -> carbon -> silica
Generator -> carbon -> CaCl2
Generator -> sulphuric -> carbon (would seem the best possible)
The orange / brown is odd. I can appreciate your mention of the water and gels (and now see that you were talking about forming it as opposed to
hydrolyzing a preprepared batch, I think; still doesn't happen with damp solvents and AlI3 as far as I've seen), but the orange...? Intriguing my dear
watsons...
Also, getting rid of the darn sulphuric in the HCl(g) is going to be vital for another reason in that it's a B/L acid, which will alter the
demethylating properties of a Lewis acid and potentially have it pulling things off where there's no active, electron donating linkage for it to
normally do so.
Edit: I'm sure I remember reading they dry most of these gases industrially with H2SO4 bubblers. I may give the HCl(g) university supplier another
call and ask for some help.
Watson, sorry, I forgot to take a photo of it prior to taking it to bits. It was simply;
3 necked flask, centre stoppered, addition funnel in a side port, tubing adaptor in the other (filled with a measured dose of CaCl2) -> wash flask
(DCM / aluminium) -> exhaust bubbler (H2SO4).
As I say, one particular point worth noting is that I obtained easily ignitable test tubes of gas at the exhaust. The only thing there that could
potentially do that would be hydrogen from the chlorination occuring or traces of DCM.
I realise the above setup is not ideal given the lack of the additional carbon / bubblers between the generator and the wash bottle. I was hopeful the
H2SO4 and anhydrous CaCl2 would be dry enough alone to work. Clearly not. Moisture likely has come over, and sulphuric.
Edit^2: I would be very grateful of suggestions for what the orange discolouration may be. I have a sneaking feeling, this one is also going to fume
like crazy when I try working it up. I would prefer to have an idea of what the sulphorous / burnt smell is prior to being gassed, again... If I know what it is, I can likely scrub it and avoid the problem the second time
round.
[Edited on 20-8-2010 by peach]
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blogfast25
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A few days ago I found out that a 'Draino Knock Out!' sulphuric acid based multi purpose 'unblocker' I bought recently was actually 95 w% H2SO4, as
opposed to the usual 50 w% I get from the same hardware store (same brand too!), by standardising it. That opens up interesting possibilities and
allows to avoid the tedious synth. of the 'poor man's conc. sulphuric acid', the bisulphates of Na, K and NH4.
I was in this thread also a little surprised at Peach's choice of CaCl2 as a source of chlorine for the production of anh. HCl (although that choice
is justified for his purposes), simply thinking that NaCl is the best and cheapest source of Cl- for that goal. Which is why I'm parking this here...
Armed with my new gadget of 94.6 w% (UN 1830) H2SO4 (with pink dye in it, aaaarghgh!) I ran some tests with CaCl2 and NaCl as sources of Cl- for HCl
generators.
As I'm not yet in a position to heat the mixture of chloride/sulphuric acid significantly I've only explored the first displacements:
NaCl (s) + H2SO4 (l) --> HCl (g) + NaHSO4 (s)
and:
1/2 CaCl2 (s) + H2SO4 (l) --> HCl (g) + 1/2 Ca(HSO4)2 (s)
I'm not sure whether the Ca(HSO4)2 does or does not disproportionate to Ca(HSO4)2 ---> CaSO4 + H2SO4 or not. I seem to have some indirect evidence
that it does.
To have a look/see I reacted 1/4 mol of NaCl with about 1/4 mol H2SO4 (there was a slight excess of acid) and 1/8 mol CaCl2 with 1/4 mol H2SO4 (there
was a slight excess of acid) and captured the HCl quantitatively in about 500 ml of water in each case. The amount of HCl generated was then estimated
by acidometry (titration with standardised NaOH).
NaCl was ordinary kitchen salt, CaCl2 was the flaky stuff for household drying purposes.
A steam bath was at the ready to help things along a bit.
First up, the CaCl2. At RT bubbling starts right away and the HCl is promptly absorbed by the water: you can see the heavier, concentrated HCl 'drip'
off the bubbles, in the form of optically denser, sinking 'swirls'. I noted no significant heat being generated.
When HCl generation seemed to falter, the reaction was pushed a little further on steam bath until bubbling in the generator had more of less ceased.
With CaCl2 a theoretical yield of about 48 % was obtained, quite disappointing.
Replicating the experiment with NaCl (equivalent in Cl- to the CaCl2) yield was even worse: 28 %! I did notice that despite
occasional swirling/shaking of the reactor the solid matter tended to clump together but I'm not sure whether this was unreactive NaCl or the reaction
product NaHSO4, probably both.
A last run was carried out with the same amount of CaCl2 but with double the amount of H2SO4 and yield was still a disappointing 61.8 %...
Note that all yields are based on first displacement only.
Is it possible that the better result with CaCl2 is due to disproportionation of the Ca(HSO4)2, thereby keeping the concentration of sulphuric acid
higher for longer?
Either way, RT generation of HCl from chloride/H2SO4 seems rather wasteful in H2SO4 consumption.
And using a strong excess of conc. H2SO4 seems to be a recipe for mechanical entrainment of H2SO4 droplets, a possible cause of error in Peach's
efforts...
[Edited on 29-8-2010 by blogfast25]
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peach
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I think I know not only which bottles you're talking about but where you're likely getting them. If it's not toolstation.com, have a look; order two
before 6pm and they'll turn up on the doorstep the next morning, for free. I buy tons of stuff from there, my TLC scratcher was from there... £2.05.
The low yield from the generator could be the 3% of water helping absorb some of the hydrogen chloride before it ever leaves the generator. The table
salt will have yielded so poorly due to the moisture content, I expect (as using diluted sulphuric does). This is why I was using laboratory grade
anhydrous calcium chloride, among other reasons; like the doubling in moles of gas I could get from the same volume in the generator. I mentioned
these points a few times earlier.
If you're just using a tube stuck into some water, you'll be loosing a fair amount of gas to the atmosphere; the test is effectively not only
measuring how well you can produce it, but also absorb it.
I put six times more hydrogen chloride than was needed through that wash bottle, so it's certainly had it's chance!  It's still sat on the surface whilst I peruse it and wait for a bit of glass to
arrive to recover the contents, which I severely doubt is what it's supposed to be, this time.
The solvent has gotten even darker, it's approaching coca cola colour now.
That pink colour; sprinkle in some peroxide, the colour goes and/or distill, 98% back.
A liter bottle of H2SO4 costs about £7 from memory, and will yield up to 36 moles of hydrogen chloride. 6 moles in a lecture bottle is £145. 
The failure will be damn moisture. With the aluminium not being hot, it seems painfully susceptible to it by comparison with the BBQ methods. That
generator has let moisture through.
If I make another attempt using purely the gas alone, it'll certainly have the additions made to clean the stream up.
I don't know if I'll try doing it directly, I'm kind of working from the ground up there. It may be more intelligent to work backwards towards
simplicity by trying some materials to give the aluminium a push in the right direction first.
Any suggestions on amounts of iodine or corrosive sublimate to try would be great. I'm only using around 5g of aluminium to save on the gas, so I
doubt it's going to need a lot.
Crikey... I may have to finally open 'that bottle' I've been avoiding. Gloves will be on if so. 
I know iodine will happily react with micronic aluminium at room temperature, in a few minutes. I would expect the HCl to displace the iodides easily
enough. What's curious is what will happen from there. Will the chlorination simply shutdown, or will 'the catalytic mass' form that seems to be
necessary. Will it form at RT, slowly? Questions, questions.
I think I'll go with iodine first, to avoid the brain melting capacity of the mercury salts and any possible amalgamation attempts.
[Edited on 30-8-2010 by peach]
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