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Author: Subject: Make Potassium (from versuchschemie.de)
aonomus
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[*] posted on 24-12-2010 at 10:29


I would argue having a large amount of available dry sodium chloride or fine free flowing sand would be the best way to deal with an alkali metal fire. One has to be careful to ensure that the NaCl or sand is dry and free flowing, as I've seen sand buckets in labs which have never been maintained, and have material akin to cement inside that would do no good for a fire. Another idea is sodium bicarbonate, it is readily available, and soaks up a ton of heat (converting from bicarbonate to carbonate, and finally to oxide if heated enough).
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UnintentionalChaos
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[*] posted on 24-12-2010 at 10:40


Quote: Originally posted by aonomus  
Another idea is sodium bicarbonate, it is readily available, and soaks up a ton of heat (converting from bicarbonate to carbonate, and finally to oxide if heated enough).


Except that alkali metals burn quite happily in CO2 and water vapor, as would be let off by the bicarbonate. You might even make the fire worse. I'd go with sand or NaCl, personally.




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[*] posted on 24-12-2010 at 11:07


One of the things which I have seen is beakers placed directly on a hot plate. That is not something I would like to do with this. Use a sand bath, it is the safest option there is. The samd sucks the oil such that it cannot pour/run off the hotplate.

I still have some Shellsol D70 left, with a lot of t-BuOK dissolved in it. After christmas, I'll try putting some Mg in this solvent and heating it. No KOH involved, no other compounds. This is close to the situation, mentioned in one of the patents in which t-amylate is reacted with magnesium.




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[*] posted on 24-12-2010 at 12:36


To circumnavigate the extortionists at Aldrich, I’ve just bought 200 g of low melting paraffin wax for microscopy purposes, MP= 56C (eBay, £1.04, not bad!). Going by the MPs of the n-alkanes (a simplification of course) this must be a C20 – C30 fraction with a density over 0.8.

Assuming that my kerosene is around C12 (going by its BP), then a mix of 1 mol wax and 1.6 mol of kerosene should give an average of around C17, with an MP of around 20C and a density of just over 0.8. About 350 g wax mixed with 270 g kerosene…

Other blends of kerosene with unblended paraffinic candle wax (no stearic acid, just alkanes - no aromatics) to increasee the density of the solvent mixture should also lead to the right balance of MP and solvent density and to achieving Nurdrage's ecellent coalescence result...



[Edited on 24-12-2010 by blogfast25]

[Edited on 24-12-2010 by blogfast25]
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[*] posted on 24-12-2010 at 12:43


@nicodem:

Most of us here are better equiped for applied research than for pure research. For that reason I think that most work here will concentrate on practicalities, how to shorten procedure time and such like...

From a safety perspective, sand bath as heating and dry, free flowing sand at the ready is probably the best we can do. Note also that the glass here is not stressed thermally a lot: all heating and cooling is done quite gradually. A sudden catastrophic failure of a glass flask is therefore not very likely... But a big RED safety blub at the start of this thread would probably make a lot of sense... :cool:

[Edited on 24-12-2010 by blogfast25]
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[*] posted on 24-12-2010 at 14:38


Quote: Originally posted by blogfast25  
To circumnavigate the extortionists at Aldrich, I’ve just bought 200 g of low melting paraffin wax for microscopy purposes, MP= 56C (eBay, £1.04, not bad!). Going by the MPs of the n-alkanes (a simplification of course) this must be a C20 – C30 fraction with a density over 0.8.



[Edited on 24-12-2010 by blogfast25]

[Edited on 24-12-2010 by blogfast25]


I wish i got to you sooner before you ordered:

I strongly urge NOT TO USE PARAFFINS WITH MELTING POINTS ABOVE ROOM TEMPERATURE!!!

This comes from my experience with candle wax as a solvent (essentially a high MP paraffin). While it works great, the problem is safety.

When it solidifies it traps tiny suspended balls of potassium making it extremely dangerous to handle. Worst of all it doesn't get destroyed when you apply alcohol, only when it's deformed or cracked do you expose the potassium.

So it seems safe when you toss it in isopropanol, it doesn't bubble or react. But then when you pick it up and it cracks or breaks the exposed potassium reacts with whatever moisture or water may accidentally be near it, then it bursts into flames. The heat melts the remaining paraffin and exposes more potassium.

Another issue is when you pour the dead mixture a thin layer of it is stuck in your flask and solidifies.

I've had several pieces of glassware bursts into flames on me due to residual wax with suspended K. I suffered no injuries but unexpected fire is definitely above my "comfort zone"


That being said, with very high diligence, high MP paraffin can be used safely if you carefully keep everything above the melting point and destroy the potassium residues, wastes, and bits with Isopropyl alcohol before labeling them "safe".

In my opinion though it's not a novice operation and not something that should be used when safer liquid alternatives are available.

If you can blend your paraffin to make it have a melting point below room temperature then go for it. Otherwise i strongly urge not to perform the experiments with solid paraffins.
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[*] posted on 24-12-2010 at 14:40


Quote: Originally posted by Nicodem  
I think it would be more interesting to do a scientific research on this reaction to figure out the mechanism of the reaction. Perhaps science is not as popular as madness, but I still think this is a great opportunity for this forum to contribute to science, given the complete obscurity of this reaction in the scientific literature (BTW, did anybody actually made a thorough literature search?).


I'm only going to contribute to pure research if i'm Co-author on the resulting paper. ;)
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[*] posted on 24-12-2010 at 17:05


I finally found a Magnesium firestarter block as a source of Magnesium to compair to the crap I got from the used anode, Im pretty sure that the anode is either some alloy or just to old and used up to much. It melts which is something I can't do with my new Mg and its activity as a fresh metal is much less.

However my slag compairs to the new fresh Mg and even a little more active so I can only imagine the power a Magnesium spong made from good fresh Magnesium would have.

Im going to focus some attention on creating some sort of magnesium spong because delving into the unknown is what keeps me interested in science else my mind starts to wounder.





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[*] posted on 24-12-2010 at 17:50


I think that after the christmas break I will attempt this synthesis, I'll make sure to grab a 1H NMR to try to determine aromatics presence (though I'm sure the low ppm shift peaks will be a complete mess). The paraffin/kerosene idea sounds the most appealing since the potassium will separate by density by itself, though the flammability is the worrying part...

[Edited on 25-12-2010 by aonomus]
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[*] posted on 24-12-2010 at 19:27


I think its OK to heat pyrex directky on a hot plate. Around here oil baths to 250C are frequently used which is basically the same operation - I have never seen one crack
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[*] posted on 25-12-2010 at 06:23


Quote: Originally posted by NurdRage  
If you can blend your paraffin to make it have a melting point below room temperature then go for it. Otherwise i strongly urge not to perform the experiments with solid paraffins.


That's THE WHOLE IDEA, nurdy, until I've found a cheaper alternative to your IR paraffin, to modify the density of lighter kerosene with heavier melted/dissolved paraffin wax, hoping that at RT such mixtures remain essentially liquid or are very low melting. Tomorrow I'll try with petroleum jelly (unadulterated Vaseline - MP = 37C) as density modifier...

For my 'left over' bits of Shellsol/kerosene that contain small amounts of K and fines, I find that treating with copious amounts of water kills it without safety issues (better than ethanol IMHO because EtOH is also flammable - see len1's minor incident). The large amount of water acts as a heat sink, thus keeping temperature close to RT and the risk of the solvent catching fire very low...

[Edited on 25-12-2010 by blogfast25]
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[*] posted on 25-12-2010 at 08:25


Quote: Originally posted by aonomus  
The paraffin/kerosene idea sounds the most appealing since the potassium will separate by density by itself, though the flammability is the worrying part...

[Edited on 25-12-2010 by aonomus]


It's not a great worry if you use decent refluxing and stay away from open flames (use sand bath or electrical hot plate)...
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[*] posted on 25-12-2010 at 10:49


Quote: Originally posted by blogfast25  


That's THE WHOLE IDEA, nurdy,


Sorry, I didn't mean to come off sounding all condescending. This is one of those experiments where the "safety zone" isn't obvious so i thought i'd explain it again to make sure nothing was missed.

If you're aware of it all then go for it and ignore my ramblings. :)

good luck, i look forward to your work, an OTC blend of solvents with exactly the right properties for maximum safety, reaction rate and coalescence properties would be awesome.
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[*] posted on 25-12-2010 at 13:45


Take a look at AW 32 hydraulic oil, it's available as high purity food grade also.
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[*] posted on 25-12-2010 at 14:18


I've been looking at smokeless parrafin for tiki torches as a possible solvent. According to the MSDS it is 99% blend of C13 and C14 straight chain alkanes. With the right boiling range of over 225 degrees Celsius. If it is smokeless the aromatic content must be incredibly low.

http://www.buytikitorches.com/category/tiki-torches-oil

MSDS for said product
http://www.buytikitorches.com/MSDS.pdf
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[*] posted on 25-12-2010 at 18:17


Even better!
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[*] posted on 26-12-2010 at 05:56


Well johnson's baby oil is actually the same as paraffin oil, right? :)
who'd have thought we be making K in baby oil...
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[*] posted on 26-12-2010 at 07:54


Quote: Originally posted by rrkss  
I've been looking at smokeless parrafin for tiki torches as a possible solvent. According to the MSDS it is 99% blend of C13 and C14 straight chain alkanes. With the right boiling range of over 225 degrees Celsius. If it is smokeless the aromatic content must be incredibly low.

http://www.buytikitorches.com/category/tiki-torches-oil

MSDS for said product
http://www.buytikitorches.com/MSDS.pdf


According to Wiki, at C14 the density is still only 0.76, too low for liquid K to float in (d = 0.828 at MP). I think you need at least C17 for floating K...
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[*] posted on 26-12-2010 at 07:56


Quote: Originally posted by NurdRage  
Sorry, I didn't mean to come off sounding all condescending. This is one of those experiments where the "safety zone" isn't obvious so i thought i'd explain it again to make sure nothing was missed.

If you're aware of it all then go for it and ignore my ramblings. :)

good luck, i look forward to your work, an OTC blend of solvents with exactly the right properties for maximum safety, reaction rate and coalescence properties would be awesome.


No condescention was detected at my end, Nurdrage, I thought you'd slightly misread my point, that's all...
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[*] posted on 26-12-2010 at 08:04


Quote: Originally posted by condennnsa  
Well johnson's baby oil is actually the same as paraffin oil, right? :)
who'd have thought we be making K in baby oil...


I think that might work, especially as they now do a 'heavier' grade, 'bay oil gel':

http://www.boots.com/en/Johnsons-Baby-Oil-Gel-200ml_6079/

It does contain some camomile (for 'extra relaxed K'?) and some other stuff we don't much care for:

Hydrogenated Butylene/Ethylene/Styrene Copolymer, Hydrogenated Ethylene/Propylene/Styrene [Copolymer, my edit], Fragrance (Chamomile Oil), Tocopheryl (Vitamin E) Acetate, Retinyl (Vitamin A) Palmitate, Corn (Zea Mays) Oils, Cholecalciferol (Vitamin D3)

So there's a bit of K's favourite food in there: OXYGEN!

And with the hydrogenated (thus inert) polymeric additives this stuff may have some weird rheological properties (non-newtonian fluid)...



[Edited on 26-12-2010 by blogfast25]
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[*] posted on 26-12-2010 at 10:09


Well, well, well...

My first attempt at ‘creating’ a solvent in which molten K would float actually failed.

Instead of carrying out an actual reaction I used some leftover K balls, mostly some 2 mm ones, some smaller ones, some fines and some MgO. I decanted off the supernatant kerosene and replaced it with a mixture of 8 g of clean medium kerosene and 20 g of petroleum gel (Vaseline ®, MP just above body temperature). This was an estimate to get about C17 from about C12 (kerosene) and about C20 (Vaseline). No floatation was observed, not even at 200 C! I added more Vaseline to try and increase the heavy fraction and thus the density but to no avail.

Finally I ran a test tube test with pure molten Vaseline and a 3 mm ball of K and the damn thing just didn’t want to float! But it did when I added a drop of IPA, because (a small amount of) hydrogen evolved and presumably small amounts of it stuck to the (by now) ball(s), providing buoyancy…

So now I’m wondering if we’re slightly barking up the wrong tree when it comes to density: is it possible that nurdrage’s ‘floating coalescence’ isn’t just caused by high solvent density of the ‘IR paraffin’ but also by reaction hydrogen providing some lift for the nascent potassium?

Food for thought… :o

Another attempt will now be made with the 56C MP paraffin wax when it finally gets here (this time definitely no ‘thanks to the L*rd!’) and possibly baby oil (the unadulterated one).
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[*] posted on 26-12-2010 at 10:09


Baby oil is fairly high viscosity? It looks like "white mineral oil", ISO VG 10-15, viscosity 70 would have high enough specific gravity and low viscosity. They are sold as low temperature hydraulic oils (ISO 15-22) and high speed machine spindle lubricants.

http://www.seversonoil.com/pdfs/FamilyOfBrands/FO_White_Oil....

http://www.farwestoil.com/crossreference.pdf

http://www.amazon.com/Albatross-SO/dp/B002BGZZXI
http://albatross-usa.com/lilywhitesewingmachineoiliso-22.asp...

http://www.drillspot.com/products/275646/Mobil_VELOCITE_NO_6...



[Edited on 12-26-2010 by Eclectic]
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[*] posted on 26-12-2010 at 10:14


Quote: Originally posted by Eclectic  
Baby oil is fairly high viscosity? It looks like "white mineral oil", ISO VG 10-15, viscosity 70 would have high enough specific gravity and low viscosity. They are sold as low temperature hydraulic oils (ISO 15-22) and high speed machine spindle lubricants.

http://www.seversonoil.com/pdfs/FamilyOfBrands/FO_White_Oil....

http://www.farwestoil.com/crossreference.pdf

http://www.amazon.com/Albatross-SO/dp/B002BGZZXI


Nice links but no mention of densities though... But presence of naphtenics would indeed help keep viscosity low. And naphtenics tend to be a little denser: n-hexane = 0.6548, cyclohexane = 0.779, n-octane = 0.703, cyclooctane = 0.834


[Edited on 26-12-2010 by blogfast25]
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[*] posted on 26-12-2010 at 14:04


Quote: Originally posted by blogfast25  

So now I’m wondering if we’re slightly barking up the wrong tree when it comes to density: is it possible that nurdrage’s ‘floating coalescence’ isn’t just caused by high solvent density of the ‘IR paraffin’ but also by reaction hydrogen providing some lift for the nascent potassium?


Possibly, definitely something i need to test.

Next time i'm in the lab (maybe tomorrow or the day after), i'll get a hunk of my potassium, put it into IR paraffin, turn up the heat and see if it floats just like that.

If it stays down then that disproves my density theory. (if it floats it doesn't necessarily prove it though...)

We'll see what happens.

[Edited on 26-12-2010 by NurdRage]
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[*] posted on 26-12-2010 at 18:31


K floats in paraffin oil alright. I have found it difficult however to get paraffin pure enough so that the improvement in coalesence due to this floating doesnt offset the yield. I cant use nujol this way, its too expensive. After all my tests, coalescence seems a chance event, whats far more constant is the yield, and this is highest in D70. Purification takes about 1/2hr and has to be tollerated
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