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Author: Subject: Make Potassium (from versuchschemie.de)
condennnsa
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[*] posted on 19-12-2010 at 02:22


Quote: Originally posted by NurdRage  
Is the alcohol required?

During one run i hadn't added the alcohol yet but had to cancel the reaction.

So i started to clean up my fume hood and tossed the reaction mixture of paraffin oil, KOH and Mg into a water bath and to my surprise i saw some tiny but distinct flashes of lilac flames.

I had heated the mixture to 170C for ten minutes but *did not yet add alcohol* before i had to stop and cancel the run.

It might be that my parafin oil, KOH, or Mg was contaminated with some t-alcohol. and produced a minute amount of potassium. But if that wasn't the case, then my observation might mean the alcohol is not critical to the reaction.

[Edited on 19-12-2010 by NurdRage]


Interesting. But how could there be alcohol contamination considering your reagents were fresly added?

The patent only says that the alcohol is a reaction accelerator.

If it's true that it works without the alcohol, what would the process look like?

I can't believe that we're in late 2010 and this amazingly easy synthesis of alkali metals is so unknown ...

This a truly glorious outcome for this thread!
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[*] posted on 19-12-2010 at 02:59


In my experiment, the liquid become turbid more and more and at the end, it was dark grey and you only could look into the liquid for a few mm.

A crust was formed at the bottom and the balls of potassium were on top of this.

Today is the day of working up all of this and processing the pics and vids I made. Next week I hope to make a real web page about this, for the time being just the pics and vids.




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[*] posted on 19-12-2010 at 03:25


Above about 230C I found patassium can metallate some paraffins and lead to decomposition - so perhaps the temperature was a tad high.

As for the reaction without butanol - its just staight according to the overall formula. Possibly KOH has some residual solubility in D70 (I observed what could be some precipitation on heating and cooling KOH in D70 alone. In any case the reaction does not go very far.

Its a good method for producing K for the home chemist. But its not really a blight on the 21st century that its not being used elsewhere. Its quite wasteful of magnesium - in itself an expensive metal, and is very slow. My electrolysis gear produces about 80gms K in the same time that this takes to make 5.8 in similar sized aparatus. What I find most interesting about it is the reaction.

[Edited on 19-12-2010 by len1]
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[*] posted on 19-12-2010 at 05:53


There is, however, one very important difference between this reaction and the electrolysis you performed. This reaction can be carried out with only very simple apparatus, while the electrolysis requires a much more elaborate setup. This reaction makes obtaining elemental potassium much more feasible for a broader range of amateurs.

So, in terms of efficiency, both in used chemicals and required energy, the electrolysis is much better, but in terms of feasibility for a broad range of amateur chemists, this reaction is better.




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[*] posted on 19-12-2010 at 06:48


Quote: Originally posted by len1  
But here is an interesting observation. The KOH liquifies at about 150C in the D70 - at the point where initial reaction with Mg is observed - so this is a liquid-solid, not solid-solid reaction, and so is expected to go a lot better. The liquification is due to the crystalization water in the KOH - which however is not evolved at this temperature (in the dry it starts dehydrating at about 250C). So Mg is needed to dehydrate the liquid KOH, whereupon it is locked inside a dry KOH lattice. Any quality Mg I believe will work in the dehydration stage.

[Edited on 19-12-2010 by len1]


Well, in my test hydrogen started to evolve way before that: 50 - 70 C. Will try and confirm that today.

Interesting points about the amount of H2 and MgO.

What about using octane (readily available as lead free high octane car juice) as a work up fluid: very low viscosity... Won't boil on steam bath but you sure do need a decent consenser...
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[*] posted on 19-12-2010 at 08:38


This is my writeup of the reaction, with pictures and a few videos:

http://woelen.homescience.net/science/chem/exps/synthesis_K/...

Have fun reading it. It might be changed in the next few days, but I now already want to share the pics and videos. Forgive me if there are still some typos or other errors.




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[*] posted on 19-12-2010 at 09:04


Very nice woelen, excellent write-up as per usual.
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[*] posted on 19-12-2010 at 09:12


I really love this synthesis. I'm also gonna try it in January.
I ordered 250g of magnesium fillings for Grignard from Carl Roth. Are these fillings suitable? What did you use woelen? Did you attempt to make the Mg metal oxide-free?
My hotplate will go to 250C, but i think it won't be able to reach a temperature of 220C if I am using a sand bath, so I will put the erlenmeyer straight on the hotplate, and put the hotplate inside a tray.
Woelen, can you try the same reaction using 'lampenolie' ? As far as i know , this is also hardly contains aromatics and has a high boiling point. If it works I won't have to buy the Shellsol (I don't have a lot of money at the moment). i can't try it myself as I first need to obtain some t-butanol (i don't want to buy a liter, so I'm looking for a source where I can obtain about 50-100mL.
Finnally, is the glass etched when performing this reaction. Although the solvent hardly solvated the KOH, I can imagine that the very hot solid KOH etches the surface of the erlenmeyer?

Has anyone tried this with the preparation of other reactive metals? Metals like barium and strontium would be interesting, but they cannot be isolated I think, because their melting point is simply too high.
Sodium does not seem interesting when you can obtain it, as it is very cheap (about 15 cents per gram for me).
Now this would be a very interesting way to make lithium, but it's really a bummer that lithium has such a low molecular weight, making it impossible to make acceptable amounts of lithium.
But who has either RbOH or CsOH? It would be awesome to make some of the beautiful golden metal! I think CsOH could be made from CsCl (I have 100g of this) by either decomposition of the insoluble CsMnO4 and dissolving in water (woelen told this in an earlier topic) or heating CsCl with conc. H2SO4, diluting and neutraling, and adding a solution of barium hydroxide. However I have no idea how to get the CsOH in a solid form from the solution without damaging glass or any plastic container you use. i think you need a TEFLON vessel.

[Edited on 19-12-2010 by Jor]

[Edited on 19-12-2010 by Jor]
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[*] posted on 19-12-2010 at 09:45


My second run still used the old Shellsol but I made two small modifications:

1. 1 ml t-butanol in 1 ml Shellsol, so slightly higher amount of alcohol.
2. addition of alcohol/Shellsol all at once at the end of ‘step 1’.

Well, well well. That was kind of interesting. I simply couldn’t really add all the t-butanol at once because of very strong reflux, with whiffs escaping from the top of the cooled refluxer tube! I started adding at about 180C, about 30 mins into the run and with difficulty and almost violent refluxing managed to add it all in about 5 mins. I’m sure I lost some alcohol, some water or both through the refluxer top. I very much did not see that yesterday. It really looks (but it may be perception pure and simple) that reaction takes place the moment the alcohol hits the solvent, with such a much invigorated boil but no discernable temperature increase.

Secondly I can confirm that I’m seeing bubbles from about 70C onwards. Low boilers? Hydrogen?

Thirdly the K-balls were a bit larger but still no good coalescence was obtained… I’ll rinse them later on. Total duration of test 1 ½ hours.

At the end during cooling:



Tomorrow a test with ‘medium Kerosene’, FP 61C, ‘Lamp oil’, or ‘ROLF = Reduced Odour Liquid Fuel’…

I also tried to coalesce yesterday’s batch using a steam bath and White Spirits. It didn’t really work although the balls are a bit more visible. The solvent got coloured (test duration also 1 ½ hours) amber-red:



Tomorrow I’ll also try Stefan’s (GarageChemist) tip of mineral oil with IPA.
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[*] posted on 19-12-2010 at 10:02


@woelen:

Yes, very nice write up. Looks like I may just be too impatient: I’ve never gone past 2 hours and you’re talking about 3 ½ hours! Patience is a virtue and good things come to those who wait... Did you calculate yield based on the megaballs only? What value?

Looks like we’ve all agreed on a mechanism now and yes, it’s rather wasteful of magnesium…

Your phased addition of the t-butanol is probably the most practical for small scale tests, I’ll be using it in a test with ‘lamp oil’ tomorrow… One could make up larger quantities of the alcohol mix as a ‘masterbatch’ to be used on several occasions.

I like the idea of the air cooled Liebig a lot, much less messy than water...



[Edited on 19-12-2010 by blogfast25]
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[*] posted on 19-12-2010 at 12:09


@Jor: The Mg I used is pyro-grade stuff from Keten (a Polish supplier of pyrotechnical chemicals). I purchased 250 grams of this one year ago. It is 100 um size and I think it is of good quality (free of oxygen). It has a light gray metallic luster and not the dark luster of oxidized stuff. Its purity of course is somewhat uncertain, remember, it is just pyro-grade stuff, not the reagent grade you have ordered. If your grignard-grade Mg is fine enough, then it should work.

I am inclined to think that the aliphatic solvent to be used is relatively important. Two things are important:
1) Boiling range (must be a range, around 220 C or so). This allows gentle simmering of the mix. This simmering causes some gentle self-stirring, enough to make the K-globules coalesce, but not so much that there is too little contact between the reactants.
2) Aromatic and unsaturated content must be low. The solvent should be a mix of alkanes and cycloalkanes. Alkenes and aromatics are counter-productive.
I believe that any solvent which satisfies (1) and (2) does the job. I am afraid that lamp oil is less suitable. It has a higher boiling range and is more viscous.


------------------------------------------------------------

I now am thinking of how to improve the efficiency of the process. The remaining clear solvent contains a lot of K-butoxide left in solution. If you pour some of this along a glass, then within seconds the glass becomes covered by a gel-like layer. Maybe this can be used in a fresh batch of Mg with less KOH added. Hence, less losses due to water content and less Mg needed. So, it might be that if one batch is used and the solvent from that batch is used for a second batch that less Mg and less KOH and hardly any t-buOH are needed to obtain the same amount of K-metal. I hope to find some time in the period between Christmas and New-Year's eve to do some research on that.


@blogfast25: I indeed have the feeling that you did not wait long enough. The globules I see in your picture are about the same size as the ones I had after two hours. So, if you keep on simmering/heating, then you may obtain larger balls.




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[*] posted on 19-12-2010 at 12:51


Quote: Originally posted by woelen  

@blogfast25: I indeed have the feeling that you did not wait long enough. The globules I see in your picture are about the same size as the ones I had after two hours. So, if you keep on simmering/heating, then you may obtain larger balls.


Yeah, I'm pretty sure too. But I'm thinking of maybe to cut the reaction time down to, say 1 1/2 hours, and develop a work up that can coalesce the crude, formed metal really quickly, less than 1/2 hour or so... I rinsed the latest batch with kerosene and it's all potassium, once the byproduct has been washed away.

[Edited on 19-12-2010 by blogfast25]
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[*] posted on 19-12-2010 at 12:58


Hmm, this whole thread is really a Christmas gift. I said it won't work but I was proven otherwise, which I'm glad about. At least I was right about the presence of the real potassium in Pok's pics.


It also means it would work for Cs and Rb with a carefull choice of the solvent.
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[*] posted on 19-12-2010 at 13:26


Quote: Originally posted by a_bab  
Hmm, this whole thread is really a Christmas gift. I said it won't work but I was proven otherwise, which I'm glad about. At least I was right about the presence of the real potassium in Pok's pics.


It also means it would work for Cs and Rb with a carefull choice of the solvent.


Well, yeah. As long as you’re not going to attempt to break the laws of this universe like you proposed doing here:

http://www.sciencemadness.org/talk/viewthread.php?tid=15061&...
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[*] posted on 19-12-2010 at 13:36


Don't worry, I am not. :D

It would still work for Ca though. I believe in thermodynamics too.
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[*] posted on 19-12-2010 at 13:46


Quote: Originally posted by woelen  
@Jor: The Mg I used is pyro-grade stuff from Keten (a Polish supplier of pyrotechnical chemicals). I purchased 250 grams of this one year ago. It is 100 um size and I think it is of good quality (free of oxygen).


I'm also considering buying some magnesium from either Keten, or Czort. Czort has slightly better prices. Woelen, did you have any trouble with Keten with the order?, I've read on UK pyrotechnics that many people were unhappy with his lack of replies to emails and slow deliveries...

[Edited on 19-12-2010 by condennnsa]
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[*] posted on 19-12-2010 at 14:46


Quote: Originally posted by condennnsa  
Quote: Originally posted by woelen  
@Jor: The Mg I used is pyro-grade stuff from Keten (a Polish supplier of pyrotechnical chemicals). I purchased 250 grams of this one year ago. It is 100 um size and I think it is of good quality (free of oxygen).


I'm also considering buying some magnesium from either Keten, or Czort. Czort has slightly better prices. Woelen, did you have any trouble with Keten with the order?, I've read on UK pyrotechnics that many people were unhappy with his lack of replies to emails and slow deliveries...

[Edited on 19-12-2010 by condennnsa]


You can buy a wide selection of different Mg powders from eBayers. I’m no longer convinced the grade is as critical as we once believed, in the Dark Ages of three weeks ago. About 4 people have managed it, all with differently sourced materials. There may be slight differences in how one grade reacts vis-à-vis another but anything that’s not too oxidised will probably do the trick… before we establish which grade is ‘optimal’ any of real magnesium should be a decent choice. Keten is slow, I can honestly confirm that…

[Edited on 19-12-2010 by blogfast25]
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[*] posted on 19-12-2010 at 15:02


Nice write up Wilco.

A couple of suggestions.

1) My experiment heating KOH in D70 with no magnesium shows that it does not dehydrate in and of itself. Mg is needed to perform this feat. Therefore I no longer believe any water is given of by the reaction, and the white turbid fumes and liquid apparent on the surface of the liebig at 150C are just D70 spray thrown up by the H2 evolution.

2) The gasometer H2 experiment shows that the hydrogen evolution is much too great for Mg(OH)2 to tbe the final product. The second formula therefore looks like this


(t-BuO)2Mg + KOH -> MgO + t-BuOK + t-BuOH

with the regenerated alcohol reacting with some of the potassium already formed. This I believe is what helps coalesce the potassium.

The propagation equations are then

2t-BuOK + Mg -> (t-BuO)2Mg + 2K
(t-BuO)2Mg + KOH -> MgO + t-BuOK + t-BuOH
K + t-BuOH -> t-BuOK + 1/2H2

summing these gives the overall reaction

Mg + KOH -> MgO + K + 1/2H2. (1)

If the second equation was

(t-BuO)2Mg + 2KOH -> Mg(OH)2 + 2t-BuOK

the overall reaction would be

Mg + 2KOH -> Mg(OH)2 + 2K (wrong) (2)

meaning no hydrogen is evolved (and using up 1/2 less magnesium for the same amount of K generated), contrary to experiment, which shows hydrogen to be evolved at a rate close to (1) above.

[Edited on 20-12-2010 by len1]
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[*] posted on 19-12-2010 at 15:06


I did not believe that it would work, I could not explain Pok's results but they seemed unlikely to me.
On the basis of the above results it definitely does work and it is a nicer procedure on a small scale than electrolysis of potassium hydroxide.
Congratulations to Pok and the successful experimenters.
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[*] posted on 20-12-2010 at 00:00


Please all read this thread Here . For further understanding where im comming from.

I got ahold of a sacraficial Mg anode from an old water heater. I have confirmed it contains Mg although I can comment on the purity since I only got it to ignite a couple times and that was only after blasting it with an acetalyne torch. To make it stanger it was normally only the slag I could get to ignite and not the molten metal this is quite possible due to to much heat being carried away while in its moltan stat. This all seems off topic but bear with me.

See I had some clean metal and I have some "slag" and I have a semipure halfway inbetween pure and "slag".

Well after dropping the three samples into H2O as expected hydrogen was released, BUT, expecting the pure metal to be the most reactive went against intuition. The dirtiest slag that I had reacted right away producing H2 in abundence. The lumpy, shiny yet not quite pure was second in hydrogen production.... However....

The cleanest forms I produced and then cut into strips(some cut even finer to represent shavings) was by far the lest reactive of all, taking sometimes between 10-15minutes before the reactivity caught up with that of the dirty metal.

Prehaps the repeated failiars of this Potassium experiment where not due to shitty Mg or improper reaction conditions but had more to do with time frame and reactivity/purity of the Mg used. Higher purity may not mean better results in this reaction or atlest force an extended reaction time since initiation took much longer then the dirty Mg did.

I can only assume that the shitty slaggy Mg skimmed off the top was so much more reactive due to the larger surface area of active Mg laced into a matrix of oxide and the semi dirty was pretty reactive due to the fact that it also had higher surface area to react with.

Im left with a hypothesis here that Magnesium ribbon is almost doomed to failiar without extended reaction time or prior sanding of the Mg surface to allow larger reaction area.


I think that If I decide to perform this reaction using the Mg(possible alloyed Mg or what ever it is I have) I will first melt down the Mg and then slowly drip it into a cold hi boiling point solvent to make a high surface area simular to mossy zinc if possible. This coupled with Finely ground KOH(NaOH in the experiment I plan on performing because my KOH is a solution at the moment) should allow the fine particals of Alkalihydroxide to settle into the pores giving intimant contant between the two reagents at work.

Hope this helps some one its a work in process and just a few observations I just noticed while attempting to clean up Magnesium for scientific use.

GL
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[*] posted on 20-12-2010 at 01:05


@Len1: Thanks for your feedback. This evening I'll modify the webpage. Good that you did the experiment of collecting the gas, so we have strong experimental backup of your proposed reaction equations.

@condennnsa: I also found Keten to be slow. The quality of their products, however, is good. I'll have a look at the Czort site, I did not know that.




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[*] posted on 20-12-2010 at 01:33


Quote: Originally posted by len1  
Its quite wasteful of magnesium - in itself an expensive metal, and is very slow. [Edited on 19-12-2010 by len1]


Yes wasteful of Mg without a doubt however Aluminum or quite possibly Zinc should perform a simular function as long as the passivation issue was handled. I had plans on attempted an amalgumated Al variation but I first want to get traditional methods to work first before adding one variable at a time.

Now if you look at my above post I do feel that the Mg can be activated in such as way to dramaticly cut down this reaction time but its gonna be a couple weeks before I can perform some definitive labwork.

[Edited on 20-12-2010 by Sedit]





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[*] posted on 20-12-2010 at 02:08


Hey cool, I'm not harmless anymore. :D :cool:
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[*] posted on 20-12-2010 at 02:20


Hey man people spend years and years with no title of there own, you should look at that as a great achievment... If possible I would like to have some length conversations with you tommorow Via PM about the Mg used and a few other things if thats ok with you. Now for me its sleepy time though.




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[*] posted on 20-12-2010 at 03:18


I have attempted this synthesis using paraffin oil (paraffinum liquidum from official chem supplier) and found the parafin getting very viscous and smelly. Of course, paraffin is not exactly a well defined substance, but it this particular bottle is negative on bromine test. What sort of reactions could paraffin undergo that d70 does not? Naphtalenics perhaps?

[Edited on 20-12-2010 by Cloner]
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