| Pages:
1
..
52
53
54
55
56
..
66 |
blogfast25
International Hazard
Posts: 10562
Registered: 3-2-2008
Location: Neverland
Member Is Offline
Mood: No Mood
|
|
Hard and brittle things grind down well in a mortar and pestle. But I imagine Ca metal is too malleable for that. Ball mill grinding (see e.g. Al
powder) could work but you need inert atmosphere.
It's probably possible to 'atomise' Ca the same way spherical Al is produced: by rapid cooling/solidifying of an aerosol of liquid Al. Not for us
hobbyists, I'm afraid...
[Edited on 29-4-2013 by blogfast25]
|
|
|
blogfast25
International Hazard
Posts: 10562
Registered: 3-2-2008
Location: Neverland
Member Is Offline
Mood: No Mood
|
|
Yesterday I prepared some more potassium, this time with a scaled up and upgraded set up but the results weren’t as good as I had hoped for. I
scaled up from 50 ml solvent to 150 ml solvent and used 2-methyl butan-2-ol as catalyst (adjusted for MW vis-à-vis t-butanol) and Shellsol D70 as
solvent (I had no deodorised kerosene left, so used up most of my remaining Shellsol D70), here’s the setup:
So, a 250 ml flat bottom RBF, an oversized Allihn condenser (no cooling water or air but I had air on standby) and heated by a temperature regulated
oil bath.
All in all it went very uneventfully although the sudden burst of hydrogen (early reaction of KOH water with Mg) was particularly violent this time
and some white mist did manage to escape through the chimney, due I believe to mechanical entrainment by the sudden hydrogen flux.
Bath temperature settled first at about 207 C, then climbed steadily to nearly 220 C. I refluxed for about 4 hours, detail:
As at some point the solvent started to cloud over (due to fine MgO I think) so I couldn’t see any potassium globules being formed, until at the end
after cooling to below 70 C this crap shoot shot showed them:
Once the solvent was removed it became clear though that coalescence this time had been quite sub normal, with only relatively few medium sized
potassium globules ready for picking:
Checking the left over dark grey sediment (not shown) I found it to be mostly potassium fines and MgO. I found no residual Mg metal. Some of the MgO
slag was very coarse, almost rocky, making further K recovery difficult, so I decided not to bother.
I believe that in this instance the lack of any stirring was partly to blame for the poor coalescence: this upgraded set up is too
rigid to even swirl the flask occasionally. Absence of any stirring may also promote MgO agglomeration. Slow, steady stirring just to keep everything
in motion is what I would recommend to any first time experimenter.
I also have been thinking for a while now that there must be a better way of harvesting the potassium than 3 hours of additional refluxing. I had
found higher up that in the right conditions the actual reduction reaction seems to be over in about 1 – 2 h tops, judging by hydrogen evolution
which tails off dramatically after about 1 h of refuxing. Checking hydrogen evolution periodically is of course easy: fill a test tube with the off
gases that leave the condenser and check for hydrogen with a match, lighter or Bunsen.
After cessation of reaction, the reactor could then be cooled down to below 80 C, the supernatant solvent removed and replaced by fresh kerosene and
this mixture of fines (MgO + fine potassium) treated much the way one pans for gold: here the lighter potassium will ‘travel’ further than the
denser MgO (d = 3.58 kg/L). The relatively MgO free potassium should be fairly easy to coalesce at around 100 C.
Another observation (which I’ve made several times) is the following. One objective of this test was to explore the possibility of catalyst
recovery/recycling. I’ve noticed many times that the supernatant post-reaction solvent, when decanted off and allowed too cool settles to a viscous,
even jelly like material. The proposed reaction mechanism predicts that all catalyst is present in the solvent as the relevant potassium alkoxide,
thus the solvent should in principle be recoverable without further to do.
Alternatively, treatment with acid should hydrolyse the potassium alkoxide to salt and the alcohol in question (but the alcohol is soluble in the
solvent, of course). Today I checked the supernatant liquid that I had set aside and a whitish, jelly like precipitate had separated out. Could this
be potassium 2-methyl butan-2-oxide? I’ve yet to decide what to do with it but there’s enough for two small scale tests.
Finally, another word of caution to those who are new (and old!) to handling potassium. Yesterday I very foolishly disregarded (probably due
to tiredness and being in a hurry) the advice I dished out to ‘elementcollector’ and used methylated spirits, INSTEAD F A LOT OF ISOPROPANOL, to
react away the fines. The ethanol immediately caught fire, the flame struck inside the small meths HDPE bottle and trying to douse the flames my hand
caught fire. I managed to extinguish the fire on my hand quickly and managed also to place the cap on the bottle to deprive it of oxygen. That worked
but caused some more burning meths to land on my hand. After extinguishing that too, a large glass beaker was put over the primary fire and that died
down instantly.
My hand suffered no lasting consequences but it did hurt a bit for most of the evening. Today it’s fine without even a scar as a memento, although
it’s definitely hairless!
So, please take great care in disposing of unwanted potassium and use a large amount of IPA, while stirring constantly and do it where you can’t set
fire to anything.
[Edited on 5-5-2013 by blogfast25]
|
|
|
elementcollector1
International Hazard
Posts: 2684
Registered: 28-12-2011
Location: The Known Universe
Member Is Offline
Mood: Molten
|
|
I should probably mention that when I thought I was using isopropanol, it turned out to be a weak solution of HCl that I had forgotten about.
This explains a lot.
Elements Collected:52/87
Latest Acquired: Cl
Next in Line: Nd
|
|
|
blogfast25
International Hazard
Posts: 10562
Registered: 3-2-2008
Location: Neverland
Member Is Offline
Mood: No Mood
|
|
EC: even IPA isn't ideal because it's also flammable. But it's the lesser of evils compared to methanol, ethanol or water, especially with finely
divided potassium.
|
|
|
MrHomeScientist
International Hazard
Posts: 1806
Registered: 24-10-2010
Location: Flerovium
Member Is Offline
Mood: No Mood
|
|
I don't like using isopropanol, personally - no matter what I do it always catches fire. In my last attempt I used a Petri dish full of IPA and
dropped in very small spatula-fulls one at a time. Each time, there was a hiss, crackle, sparks, and ignition of the dish. Easy enough to blow it out,
but still dangerous. In my experience, even if you use a lot of IPA to stop the potassium reaction from heating the liquid to its ignition point, the
sparks produced still ignite the alcohol vapor floating over the surface.
Instead I just use a big bucket of water, halfway full, and pour in ~10mL at a time. It certainly doesn't like that, but at least water isn't
flammable. If you don't fill the bucket up all the way and go slowly, nothing will splash out at you.
|
|
|
blogfast25
International Hazard
Posts: 10562
Registered: 3-2-2008
Location: Neverland
Member Is Offline
Mood: No Mood
|
|
I guess you're right, Mr HS, plain ole' water in copious amounts and away from flammable vapours is probably still best.
|
|
|
Vargouille
Hazard to Others
Posts: 380
Registered: 16-4-2012
Member Is Offline
Mood: No Mood
|
|
I was under the impression that potassium was quenched by adding it to dry hexanes/toluene, and then adding dry isopropanol slowly. The hexanes
dilutes the isopropanol to keep the reaction from being too vigorous, as does the slow addition of the alcohol.
|
|
|
Toluene
Harmless
Posts: 26
Registered: 19-5-2013
Member Is Offline
Mood: No Mood
|
|
Hello, I have a couple of questions: Did anybody try to use another alcohol as catalyst? I have already ordered my t-butanol ,but til it arrives I
decided to take a look at household chemicals, I found an interesting alcohol:ethylenglycol (ethanodiol) I know it is not a three or more carbons
alcohol so, my question is : should I give a try with the ethylenglycol or I'm just wasting my time?
Another question. I have read the whole thread and I saw that some people say that sodium might be reduced with aluminium did anybody try this?
|
|
|
elementcollector1
International Hazard
Posts: 2684
Registered: 28-12-2011
Location: The Known Universe
Member Is Offline
Mood: Molten
|
|
There have been attempts with non-tertiary alcohols, but no successes with these so far. Only tertiary alcohols seem to work.
Elements Collected:52/87
Latest Acquired: Cl
Next in Line: Nd
|
|
|
MrHomeScientist
International Hazard
Posts: 1806
Registered: 24-10-2010
Location: Flerovium
Member Is Offline
Mood: No Mood
|
|
If you've actually read the whole thread, then you'd know other alcohols have been tried with little success. The only other one confirmed to work so
far is t-amyl alcohol, with others failing for various reasons. I posted a sort of "summary" of the thread back on page 51, I believe, if you don't
want to actually read the entire thread. I just copied down posts that were relevant to my own experiments so it certainly leaves out a lot of
information, but it's a start.
|
|
|
Toluene
Harmless
Posts: 26
Registered: 19-5-2013
Member Is Offline
Mood: No Mood
|
|
Quote: Originally posted by MrHomeScientist  | | If you've actually read the whole thread, then you'd know other alcohols have been tried with little success. The only other one confirmed to work so
far is t-amyl alcohol, with others failing for various reasons. I posted a sort of "summary" of the thread back on page 51, I believe, if you don't
want to actually read the entire thread. I just copied down posts that were relevant to my own experiments so it certainly leaves out a lot of
information, but it's a start. |
Yes, I downloaded your word sheet, is just that I'm a bit anxious to try the reaction
btw, what about aluminium reducing sodium?
|
|
|
MrHomeScientist
International Hazard
Posts: 1806
Registered: 24-10-2010
Location: Flerovium
Member Is Offline
Mood: No Mood
|
|
The issue with using this reaction to produce sodium is that the sodium alkoxide is much less soluble in the reaction solvent than the potassium
counterpart, so it's much less (or possibly not at all) effective as a catalyst. The thought was that creating a longer chain tertiary alcohol would
be necessary for Na, and there was a separate thread created in the Organics section devoted to it (this has been linked to in this thread a number of
times). I don't think there was much progress on that front, unfortunately.
I was certainly anxious the first time too, especially since each failure represents 4 hours of lost time! It went surprisingly well for me in my
trials, though, except for coalescence. I think I'm just not running at a high enough temperature. As long as you follow the procedures that have been
proven to work by other members, you should hopefully be in the clear.
For your enjoyment, here's a short clip of me trying to dispose of the unrecoverable potassium fines. First in isopropanol, then a big bucket of
water. http://www.youtube.com/watch?v=KF79gF81-Dw
It's a very angry reaction in both, but at least the water doesn't catch fire! Use a large bucket, and slow addition. If you only fill it halfway, any
splatters from the crackling K are contained in the bucket.
|
|
|
Toluene
Harmless
Posts: 26
Registered: 19-5-2013
Member Is Offline
Mood: No Mood
|
|
Thank you so much for the video is awesome how the isopropanol reach enough temperature to self ignite.
As for the sodium how much longer has to be the chain? 6 carbons?
|
|
|
MrHomeScientist
International Hazard
Posts: 1806
Registered: 24-10-2010
Location: Flerovium
Member Is Offline
Mood: No Mood
|
|
I think it's not that the IPA gets hot enough to self-ignite - rather, the sparks produced by the reacting K are capable of igniting the alcohol vapor
floating nearby.
I was never involved in the research for sodium production, so I don't have much information about it. I'd recommend you take a look at the "synthesis
of longer tertiary chain alcohols" thread in the Organics section (at least I think that's what it was called).
|
|
|
blogfast25
International Hazard
Posts: 10562
Registered: 3-2-2008
Location: Neverland
Member Is Offline
Mood: No Mood
|
|
| Quote: Originally posted by Toluene | Hello, I have a couple of questions: Did anybody try to use another alcohol as catalyst? I have already ordered my t-butanol ,but til it arrives I
decided to take a look at household chemicals, I found an interesting alcohol:ethylenglycol (ethanodiol) I know it is not a three or more carbons
alcohol so, my question is : should I give a try with the ethylenglycol or I'm just wasting my time?
Another question. I have read the whole thread and I saw that some people say that sodium might be reduced with aluminium did anybody try this?
|
We're 99 % certain that only t-alcohols work: primary and secondary alcohols get chewed up very quickly in these hot, alkaline conditions. The choice
of using a tertiary alcohol must have been a very deliberate one on the part of the inventors and based largely on tertiary alcohol's resistance to
oxidation in alkaline conditions. p- and s- alcohols oxidise fairly easily to corresponding aldehydes, ketones or acids.
Apart from t-butanol, 2-methyl butan-2-ol (aka 2M2B) also works perfectly, it's the one I use. Longer chain (C5, C6 and higher) t-alcohols of the
general structure 2 methyl alkan-2-ol could work too but are less available and as yet largely untested.
Sodium hydroxide can be reduced with Al in very messy, thermite-like conditions but it's highly unlikely to work here. Still, be a trailblazer and be
the first to try it!
Magnesium seems eager to form structures like R-Mg- and R-O-Mg- (see Grignard Reactions), of aluminium that is not so evident (at least not to me)...
[Edited on 21-5-2013 by blogfast25]
|
|
|
Toluene
Harmless
Posts: 26
Registered: 19-5-2013
Member Is Offline
Mood: No Mood
|
|
| Quote: Originally posted by blogfast25 | | Quote: Originally posted by Toluene | Hello, I have a couple of questions: Did anybody try to use another alcohol as catalyst? I have already ordered my t-butanol ,but til it arrives I
decided to take a look at household chemicals, I found an interesting alcohol:ethylenglycol (ethanodiol) I know it is not a three or more carbons
alcohol so, my question is : should I give a try with the ethylenglycol or I'm just wasting my time?
Another question. I have read the whole thread and I saw that some people say that sodium might be reduced with aluminium did anybody try this?
|
We're 99 % certain that only t-alcohols work: primary and secondary alcohols get chewed up very quickly in these hot, alkaline conditions. The choice
of using a tertiary alcohol must have been a very deliberate one on the part of the inventors and based largely on tertiary alcohol's resistance to
oxidation in alkaline conditions. p- and s- alcohols oxidise fairly easily to corresponding aldehydes, ketones or acids.
Apart from t-butanol, 2-methyl butan-2-ol (aka 2M2B) also works perfectly, it's the one I use. Longer chain (C5, C6 and higher) t-alcohols of the
general structure 2 methyl alkan-2-ol could work too but are less available and as yet largely untested.
Sodium hydroxide can be reduced with Al in very messy, thermite-like conditions but it's highly unlikely to work here. Still, be a trailblazer and be
the first to try it!
Magnesium seems eager to form structures like R-Mg- and R-O-Mg- (see Grignard Reactions), of aluminium that is not so evident (at least not to me)...
[Edited on 21-5-2013 by blogfast25] |
Thank you very much, My t-butanol at last arrived!, so, the sodium then may be reduced by the magnesium in the conditions of this experiment?, just
using NaOH instead of KOH?
[Edited on 24-5-2013 by Toluene]
[Edited on 24-5-2013 by Toluene]
|
|
|
blogfast25
International Hazard
Posts: 10562
Registered: 3-2-2008
Location: Neverland
Member Is Offline
Mood: No Mood
|
|
| Quote: Originally posted by Toluene | [
Thank you very much, My t-butanol at last arrived!, so, the sodium then may be reduced by the magnesium in the conditions of this experiment?, just
using NaOH instead of KOH?
|
Sodium is much more problematic than potassium with this method. Consult the original patent (see top of this long thread) to get a good idea of that
difficulty.
Some (like me) believe longer chain t-alcohols might work better for sodium but as yet that remains an unproved hypothesis.
[Edited on 25-5-2013 by blogfast25]
|
|
|
hyfalcon
International Hazard
Posts: 1003
Registered: 29-3-2012
Member Is Offline
Mood: No Mood
|
|
I'm going to give this a shot. My t-butanol came in the other day. Will this be a good substitute for the Shellsol D70?
http://images.tikibrand.com/lamplight/llfwholesale/knowledge...
Boiling point seems to be about the right range.
|
|
|
blogfast25
International Hazard
Posts: 10562
Registered: 3-2-2008
Location: Neverland
Member Is Offline
Mood: No Mood
|
|
Yes, as perfect as can be.
I'm always glad to see someone else having a stab at this preparation, so good luck!
[Edited on 26-5-2013 by blogfast25]
|
|
|
Toluene
Harmless
Posts: 26
Registered: 19-5-2013
Member Is Offline
Mood: No Mood
|
|
Hello,
Yesterday I tried to produce sodium metal from NaOH, aluminium and the T-BuOH, I grinded aluminium foil in a coffee grinder to make it finer, I
followed all the instructions and I got nothing, the truth is that I didn't measure the reagents properly since my precision scale hasn't arrived yet,
I'll keep trying on this method
|
|
|
plante1999
International Hazard
Posts: 1936
Registered: 27-12-2010
Member Is Offline
Mood: Mad as a hatter
|
|
It need magnesium, not aluminium.
I never asked for this.
|
|
|
Toluene
Harmless
Posts: 26
Registered: 19-5-2013
Member Is Offline
Mood: No Mood
|
|
| Quote: |
Yes, that is what it seems, but, If you can reduce it with aluminium under thermite conditions, why not try in this ones?, By the way, the sodium
hydroxide turned brownish after 3 hours of refluxing and adding the catalyst, but the aluminium is still pretty shiny  |
|
|
|
blogfast25
International Hazard
Posts: 10562
Registered: 3-2-2008
Location: Neverland
Member Is Offline
Mood: No Mood
|
|
Toluene:
As I wrote on 21/5:
"Magnesium seems eager to form structures like R-Mg- and R-O-Mg- (see Grignard Reactions), of aluminium that is not so evident (at least not to
me)..."
You're comparing apples and oranges. The reaction with magnesium requires a specific catalyst, clearly specific TO Mg, not to Al.
[Edited on 27-5-2013 by blogfast25]
|
|
|
Toluene
Harmless
Posts: 26
Registered: 19-5-2013
Member Is Offline
Mood: No Mood
|
|
| Quote: Originally posted by blogfast25 | Toluene:
As I wrote on 21/5:
"Magnesium seems eager to form structures like R-Mg- and R-O-Mg- (see Grignard Reactions), of aluminium that is not so evident (at least not to
me)..."
You're comparing apples and oranges. The reaction with magnesium requires a specific catalyst, clearly specific TO Mg, not to Al.
[Edited on 27-5-2013 by blogfast25] |
Thank you, since my magnesium seems that doesn't want to arrive, I'm trying it with a metal sharpener (wich I think doesn't have a very pure magnesium
content), results this night  r
|
|
|
blogfast25
International Hazard
Posts: 10562
Registered: 3-2-2008
Location: Neverland
Member Is Offline
Mood: No Mood
|
|
I’ve been toying with the idea of recovering the catalyst in some way or other and have made a first step in that direction today. As I wrote above
on this page:
| Quote: Originally posted by blogfast25 |
Another observation (which I’ve made several times) is the following. One objective of this test was to explore the possibility of catalyst
recovery/recycling. I’ve noticed many times that the supernatant post-reaction solvent, when decanted off and allowed too cool settles to a viscous,
even jelly like material. The proposed reaction mechanism predicts that all catalyst is present in the solvent as the relevant potassium alkoxide,
thus the solvent should in principle be recoverable without further to do.
Alternatively, treatment with acid should hydrolyse the potassium alkoxide to salt and the alcohol in question (but the alcohol is soluble in the
solvent, of course). Today I checked the supernatant liquid that I had set aside and a whitish, jelly like precipitate had separated out. Could this
be potassium 2-methyl butan-2-oxide? I’ve yet to decide what to do with it but there’s enough for two small scale tests. |
The supernatant with its white/greyish precipitate had been parafilmed and set aside for a few weeks and the consistency of the liquid had returned
completely to that of the virgin solvent. The precipitate had collected at the bottom. This was filtered off and washed with a bit of xylene (the only
solvent I had at hand that is miscible with kerosene and is quite volatile too), then it allowed to dry for a few days. It then looked like this (on a
110 mm filter paper):
There’s 4.17 g of it.
This was mixed with about 20 ml of water but it’s quite hydrophobic. Then slowly about 30 ml of 36 % HCl was added. It turned out that the darker
matter was mostly unreacted magnesium, so the addition was done carefully and the solution heated up very considerably.
If the product contains potassium alkoxide then it should have been hydrolysed acc.:
KOR + HCl → KCl + ROH
Half way through the HCl addition I could already see an oily phase beginning to form on top. After the addition, most of the watery phase (presumed
MgCl2 + KCl solution) was separated with a separation funnel, the rest of the mixture was decanted off into a normal size test tube. The organic phase
(quite murky) can clearly be seen:
Although it smells of 2-methyl-2-butanol (t-amyl alcohol, the catalyst used) it can’t be excluded that traces of the original kerosene or xylene may
be present in this organic phase. I happen to have a micro-still (max capacity 3 ml) and will now try and distil over the presumed 2M2B to get a crude
BP.
Edit:
The micro-distillation’s results were a bit inconclusive: 0.5 ml (or thereabouts) is a bit little for a pre-distillation work up and just adding
some CaCl2 didn’t really cut it. The result was bumpiness and no way to determine an accurate BP. I did get three drops of turbid distillate that
reeked of 2-methyl-2-butanol. But it’s probably heavily contaminated with water and some of the excess HCl.
This is the micro-still:
Right: thermometer; Centre: silicone oil bath and boiler; Bottom: micro-burner (methanol); Top: still head; Left: fractionating tray.
[Edited on 1-6-2013 by blogfast25]
[Edited on 1-6-2013 by blogfast25]
|
|
|
| Pages:
1
..
52
53
54
55
56
..
66 |
![[*]](images/xpblue/default_icon.gif){kind=icon}
