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condennnsa
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Yes it really is beautiful crystals! And a very strong interesting smell!
Kind of reminds me of those cheap minty candies, which is worrisome.
I didn't know it shrinks when freezing, that is reassuring. I guess i don't have to worry.
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blogfast25
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I second mr crow: no risk of cracking, it's not water based.
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condennnsa
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mr crow, are you sure about the t-butanol shrinking on freezing?
because mine has been for 2 hours over a heater and the still frozen piece is obviously floating in the melted alcohol.
though very little of it protrudes from the surface.
it could also be the water in my alcohol messing things up, as the label lists water<0.1%
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mr.crow
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So its like an iceberg. I couldn't find any evidence online, but my experience is freezing isn't a problem. If it does expand it will be a lot less
than what water does and the pressure will go upwards towards the air gap above the liquid.
Double, double toil and trouble; Fire burn, and caldron bubble
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blogfast25
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Quote: Originally posted by condennnsa  | mr crow, are you sure about the t-butanol shrinking on freezing?
because mine has been for 2 hours over a heater and the still frozen piece is obviously floating in the melted alcohol.
though very little of it protrudes from the surface.
it could also be the water in my alcohol messing things up, as the label lists water<0.1%
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Is the frozen piece solid t-butanol or does it contain air pockets?
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condennnsa
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you're right blogfast, upon close inspection i see that frozen piece has lots of air bubbles.
[Edited on 4-2-2011 by condennnsa]
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blogfast25
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Mine did too, that's what made me think of it. Cases where the solid is less dense that the corresponding liquid are really quite rare. Ice does it
and w/o that property there may not be life on Earth as we know it...
You guys now have enough t-butanol to make a tonne of K! Proverbially speaking at least: about 0.1 mol catalyst per mol K, work it out!
[Edited on 4-2-2011 by blogfast25]
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condennnsa
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Now that i melted it all and let it freeze again, the frozen chunks all sink to the bottom, so mr crow is right.
I guess t-butanol can dissolve gases quite well.
About the tonne of K, Blogfast, after all, isn't the solvent together with the already dissolved alcohol supposed to be recyclable? Has any of you
guys tried to have a second run in the same solvent, after getting rid of the MgO crust/sand? I guess it should work. Then one could get away with
10ml of alcohol for years.
[Edited on 4-2-2011 by condennnsa]
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blogfast25
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| Quote: Originally posted by condennnsa | About the tonne of K, Blogfast, after all, isn't the solvent together with the already dissolved alcohol supposed to be recyclable? Has any of you
guys tried to have a second run in the same solvent, after getting rid of the MgO crust/sand? I guess it should work. Then one could get away with
10ml of alcohol for years.
[Edited on 4-2-2011 by condennnsa] |
Yes, as I’ve been arguing for some time now: if t-butanol (or 2-methyl-butan-2-ol) is a true catalyst then it should be recyclable. And if
experimental proof of that would be obtained then it would be further evidence that the proposed reaction mechanism is indeed correct.
In reality it’s not that simple. Theory tells us that the catalyst at the end of the reaction should be mainly (if not solely) in the form of
potassium t-butoxide). At RT this may not be very soluble in the solvent and may separate out. My solvent after cooling is usually quite ‘jelly
like’, this may be due to separation. Then again that may not be the case, I just don’t know at this point.
The second problem is effective separation of the solvent (+ K t-butoxide) from the potassium metal and MgO. The post-reaction solvent is difficult to
filter with conventional filtration means (at least with ‘garden shed’ filtering media!) But complete separation may not even be necessary:
there’s nothing in the proposed mechanism that would indicate that small amounts of fine K or MgO would inhibit the reaction.
My advice to both of you is to not blindly throw the solvent down the drain after you’ve recovered the potassium metal, but to set it aside, well
stoppered, for further experimentation…
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condennnsa
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Well I had my first try at this.
I added 50 ml vet grade paraffin oil to a 200ml beaker, 6.1 g KOH, and 3.1 g Mg shavings.
On top of the beaker I added a glass jar filled with ice water, to act like a primitive refluxer, as I don't have a flask so small to fit my 29/32
ground joint condenser.
I put the beaker on the hot plate, and in about a minute, maybe less!, there was a very violent reaction, like woelen describes in his write-up. Lots
of splattering, and white fumes of presumably paraffin oil mist.
So there was clearly a very exothermic reaction taking place. the whole beaker heated up very fast.
I attributed this violent reaction to the magnesium reacting with the water in the KOH.
Also during this time, the 'liquefaction' of the KOH flakes took place, as described by others, particularly Len1.
After this violent reaction was over I could not believe what I was seeing in the beaker! Tiny, sub millimeter , spheres of metal! they were moving
across the solvent, and i looked very carefully, they were not gas bubbles of any kind!, they were shiny, and did not go up! I was sure thess were
potassium metal balls.
Now note that until this time I had not yet added the alcohol.
I continued to heat the beaker, the temperature stabilised at 240C, the loss of solvent was negligible, and it was not boiling. The water jar on top
was doing its job quite well.
All this time gas bubbles continued to emerge from all solids, presumably H2.
But the tiny metal balls did not continue to appear, nor did they grow in size.
I now added 0.6g t-butanol to 6ml paraffin oil, mixed it in till it was homogeneous, and put this to the beaker.
On contact, there was lots of boiling, but most of it condensed back and dripped back in. I don't think i lost a large percentage of the t-butanol due
to this boiling, as there was almost no smell of it.
The solution became cloudy, as reported by others,
but everything went wrong from there.
The metal balls disappeared, and I continued to heat the beaker at 240C for an hour, during which time the H2 evolution continued to drop...
After about 1.5 hours of heating there is still no metal balls, and the gas evolution was almost non existent.
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tnphysics
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Will Al react in this way if finely divided? It is cheaper so if it does it is to be preferred, but the reaction would need to be driven by reduction
of the water produced to H2. It may not react.
I LOVE science!
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blogfast25
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Condensa:
Very weird stuff going on there…
Some remarks/questions:
Do you know the density of your solvent? Measure it by weighing a known volume (in a measuring cylinder e.g.).
240 C seems a very high temperature for no boiling to occur. Are you sure the bubbles are H2 and not simply vapour bubbles from the solvent? These
would form preferably on the solids (acting like boiling stones).
Are you sure you saw potassium PRIOR to alcohol addition?
Your refluxer idea is probably OK but does it really provide 100 % reflux with your solvent at 240 C? Do you have ice + water in the refluxer at all
times? Also, 50 ml of solvent (plus reagents) in a 200 ml beaker leaves a lot of head space: the catalyst (its BP is only 82 C!) at this temperature
has a tendency to gather in the vapour phase of the apparatus, even IF refluxing is constant, leaving perhaps little of it in actual solution.
Did you check the post-reaction sludge for potassium?
I would suggest to:
• Try again with at least 100 ml of solvent (double also all reagents and catalyst quantities). This reduces amount of head space.
• Add catalyst right from start.
• Heat a little slower, ending up at about 200 - 220 C.
Tnphysics:
No one has tried Al powder as far as I know. Be the first!
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condennnsa
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Blogfast, i measured the density of my paraffin oil with graduate cylinder and scale, several times. It is 0.83-0.835 at room temperature.
However, during heating i could clearly see that The solvent level has risen noticeably, my guess with about 10-15%, judging by the lines on the
beaker.
Yes, I'm sure i saw metal balls before alcohol addition, just after the initial vigorous reaction began to calm down.
I even ran another test with the same oil, 3.1 KOH, 1.5 g Mg. Again the vigorous reaction, and just after that I could see maybe 40 or 50 tiny sub
millimeter metal spheres swimming around. I then heated it for 30 minutes more, during time they disappeared. In this test I did not add any t
butanol.
My refluxer was in no way making a GOOD seal. but judging by how much the solvent level dropped during one hour, I can say that the losses were very
low.
And no, ice water was only at the start, i did not replenish it. But even toward the end the water in the jar was at maybe 30-35C, it was still
condensing the paraffin quite well.
I don't know what to make of all this, i'm rather disappointed.
Blogfast, i'm reluctant to have larger batches.
I was thinking of doing it small until i find the one that works best. I want to waste as little of my chemicals as I can.
I'm also going to try it by adding the catalyst from the start, but wasn't it Len1 who came to the conclusion that part of his failure with this
reaction three years ago was because he added the alcohol at the start? He said earlier in the thread I think that there should be no alcohol during
the 'dehydration' stage..
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blogfast25
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| Quote: Originally posted by condennnsa |
I'm also going to try it by adding the catalyst from the start, but wasn't it Len1 who came to the conclusion that part of his failure with this
reaction three years ago was because he added the alcohol at the start? He said earlier in the thread I think that there should be no alcohol during
the 'dehydration' stage..
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That’s not how I recall it: Len1’s initial failure was attributed to too vigorous stirring and possibly the grade of Mg. In this thread (so, much
later!) he did claim ”that there should be no alcohol during the 'dehydration' stage..” but gave no substantiation for that claim
whatsoever.
My tests and Nurdrage’s show ‘one pot’ is possible. Nothing in the proposed reaction mechanism says it isn’t either. It has the distinct
advantage of avoiding the very strong reflux of t-butanol when you add it to the hot solvent (very much suited to your method of refluxing). It also
avoids introducing oxygen into the system…
Your solvent is borderline density for floatation and it expands during heating. But that shouldn’t stop reaction anyway. And a ‘Vet grade’
should be very pure.
Very strange you get K even without catalyst, we’d expect that to happen only at much higher temperatures (> 500 C).
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condennnsa
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Ok, so I ran another test to see if the balls I get right at the start are indeed potassium, this time with a different oil, I used pharmacy paraffin
oil.
1 g KOH and 0.5 g mg shavings, in about 12 ml oil.
Reaction proceeded in exactly the same manner, after the vigorous initial bubbling began to calm down, there were lots , maybe a hundred very tiny
metal balls swimming around, and this time with a lot of persistance i managed to get one out with a knife.
Upon adding it to water, it reacted just like potassium.
This was exciting for me, as it was the first time in my life to see sodium or potassium with water.
Any one of you guys, who has either paraffin oil, should get these balls right at the start.
Unfortunately, I still haven't had success with the t-butanol reviving this reaction.
I am yet to have a go with a one pot setup.
Every single time, after i get these metal balls, in about 10 minutes they disappear, and no matter if I add the alcohol, the hydrogen evolution
slowly dies down, and the magnesium chips get a dark grey/brown luster.
This dark grey luster got me thinking that it might be a silicon contamination which passivates the surface of the chips.
My results seem to be very similar to garage chemist's trials, for which he blamed the magnesium.
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blogfast25
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What grade of magnesium are you using? Most powdered grades of Mg, AFAIK, are unalloyed. The production process kind of dictates that (electrolysis of
molten MgCl2). Try dissolving a small amount in dilute HCl (or any other fairly pure acid - even distilled vinegar will do): you should get a clear
sloution (Si will not dissolve unless present as Mg2Si).
Still very strange you're getting potassium w/o catalyst?!?!
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condennnsa
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I have 2 types of magnesium, 63 micron and Mg shavings, both from likurg.pl.
All the trials I had so far were with the shavings.
The only test I did for shavings was by dissolving in 30% H2SO4, I dissolved about 40 grams and the solution was completely clear.
Blogfast, believe me, I am as surprised as you, but if you have doubts, try it yourself, I bet it will work. just heat under paraffin oil KOH and Mg,
and in good light I guarantee you will see the tiny balls.
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blogfast25
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I'm not doubting your word. The only time I didn't get K was when my refluxer broke and I lost all the catalyst through evaporation.
Also, paraffin/kerosene/Shellsol, it matters little, except for Tetralin (much faster acc. Nurdrage).
You'll have to try the 63 micron powder...
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Per
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I've now got the result that Mg from a pencil sharpener works pretty fine while my phlegmatised 99% Mg powder with which I made my first attempts is
not working...
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metalresearcher
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| Quote: Originally posted by condennnsa | Well I had my first try at this.
I added 50 ml vet grade paraffin oil to a 200ml beaker, 6.1 g KOH, and 3.1 g Mg shavings.
On top of the beaker I added a glass jar filled with ice water, to act like a primitive refluxer, as I don't have a flask so small to fit my 29/32
ground joint condenser.
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Interesting, I'll give it a try. Can vegetable oil or molten candle wax be used as well ? They have a higher boiling point and are readily available.
And what about the fire hazard (above 200oC virtually every oil catches fire) ?
[Edited on 2011-2-16 by metalresearcher]
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blogfast25
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metal researcher:
No vegetable oil: it contains bound oxygen: -O- + 2 K ===> K2O + much heat!
Candle wax was first used by Nurdrage. Avoid candles that contain stearic acid. Candle wax solidifies at RT, a great drawback for cleaning up the
resulting post-reaction mess.
Best cheap solvent, IMHO, is unadulterated heavy kerosene (lamp oil, very OTC).
Fire hazard: use sand bath heating. Make sure you're refluxer works properly.
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metalresearcher
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I tried with a small 100ml beaker in a pan with sand heated by a bunsen burner. On top of it I put a wide crucible to prevent much coming out in case
of a vigorous reaction. I put a thermocouple into it but it did no go further than 198oC the lamp oil boiled.
I used 0.93g KOH flakes and 0.31g Mg shavings and immersed it into 30ml lamp oil.
I doubt whether any K metal is formed. I saw some bubbling but that is probably boiling /evaporating oil.
Should I use another (heavier) oil ?
  
[Edited on 2011-2-16 by metalresearcher]
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condennnsa
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yes, the alkali metal will react to release hydrogen with the vegetable oil to give the corresponding linoleic/oleic acid salts, (soaps) . http://www.youtube.com/watch?v=5GahIcgDKPs
This reaction is draining the life out of me, I must have had 12 runs till now and I could never get it to work. I tried pyro mg shavings, 63um
powder, homemade shavings from sacrificial anode for boilers, even magnesium filings from Mg pencil sharpeners. The only potassium I saw was the one
at the beginning which disappears in 2 or 3 minutes, then nothing.
At this point , I guess that good refluxing is critical for this reaction, and I can only point to this as the culprit of my failures. I'll have to
buy some smaller volume glassware to fit my condenser and keep trying.
But then i'm still unsure, as Nurdrage if I remember had success with the higher boiling paraffin wax without refluxing at all, where he just used an
uncovered beaker, in this video http://www.youtube.com/watch?v=DUzsyNLuLyg.
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metalresearcher
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UPDATE:
I emptied the beaker of my previous experiment from amp oil and found the KOH was sticked together in the beaker. So I added some water and saw a few
sparks appearing (so there was a very little K metal formed.
Anyway, I put the Mg turnings (with still some lamp oil on it which does not affect the experiment) + fresh KOH in a steel tube of 2.5cm diameter and
5cm long one end squeezed and welded together. I put a small steel plate on the top of the open end of the tube. During heating the lamp oil remains
evaporated and burned and then the KOH reacted with the Mg metal showing purplish flames of buring K metal. Lots of smoke (probably K2O) appeared.
Here a video:
<iframe sandbox title="YouTube video player" width="480" height="390" src="http://www.youtube.com/embed/udYQQ75S3So" frameborder="0"
allowfullscreen></iframe>
[Edited on 2011-2-16 by metalresearcher]
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peach
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| Quote: | | Poppers is a slang term for various alkyl nitrites inhaled for recreational purposes, particularly amyl nitrite, butyl nitrite, isopropyl nitrite and
isobutyl nitrite. |
| Quote: | Isoamyl nitrite decomposes in the presence of base to give nitrite salts and the isoamyl alcohol:
C5H11ONO + NaOH → C5H11OH + NaNO2 |
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