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Tiny Sodium Spheres
I read in some book (I could not find the reference again) that fine sodium spheres could be prepared by melting under xylene and shaking vigorously.
I decided to replace the shaking with a magnetic stirrer.
Procedure:
About 2 grams of sodium were placed into a 125 mL RBF, followed by 30 mL of xylene and a stir bar. Next, a Vigreux column was fitted to the flask to
serve as a reflux condenser. The contents of the flask were stirred vigorously for 20 minutes with heating, although very little condensation was seen
in the column. After this time, the flask was removed from the hot plate, and the small pieces of sodium settled to the bottom.
Important notes:
Use a stir bar that is sufficiently large. I used a very small stir bar at first; it failed to pulverize the sodium.
Fear is what you get when caution wasn't enough.
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deltaH
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Nice work, well done!
This is similar to the way that air stable lithium powder is made (melting in an inert solvent and then vigorously stirring), except that in that case
a chemical is added that passivates the surface of the powder so that they become air stable (I had a thread about those somewhere on SM). Perhaps the
same can be done for sodium?
A magnetic bar is not ideal if one were after powders though, a high shear stirrer might work better... you know, like a milk frother thingy?
Just sharing some ideas for a variation, don't set your flask/lab/self on fire with them 
[Edited on 3-2-2015 by deltaH]
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Chemosynthesis
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Nice post. I wonder if you could try and alter the pellet sizes for bird shot sodium.
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Loptr
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I prepared some as well using that method. I posted a picture in Pretty Pictures 2 about a clump of sodium I ended up with after attempting it under
mineral oil.
Here is another guy making sodium beads for a preparation of ethyl acetoacetate via claisen condensation.
http://lulelaboratory.blogspot.com/2013/08/preparation-of-et...
Very nice!
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blogfast25
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There's a documented method for making 'sodium sand' on the web somewhere. It involves high shear mixing of Na metal and toluene (IIRW) just above the
MP of Na, followed by slow cooling. Quite a fine dispersion of Na in toluene can be achieved this way.
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subsecret
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Thank you for the input.
@deltaH: The spheres tarnish quickly, as I discovered that oxygen and/or water are very slightly soluble in xylene. Perhaps this would passivate the
sodium enough for transfer to another container. Then again, the passivating effect would have to be even stronger for sodium powder.
@Chemosynthesis: The original procedure stated that shaking the flask for a longer period of time would produce finer sodium. I actually swapped stir
bars halfway through the experiment, but before I did, I saw a few pieces about 2 mm in diameter come off. I might repeat this to see if I can get a
more consistent result.
@Loptr: Mineral oil is indeed a better "solvent" for this preparation. It protects from oxygen better than xylene, and viscosity would decrease anyway
at these temperatures. It also looks like I was a bit optimistic with my "2 grams" of sodium, based on that ethyl acetoacetate preparation.
Here is a video I made of the preparation:
https://www.youtube.com/watch?v=psgVNkBNNUc
[Edited on 3-2-2015 by Awesomeness]
Fear is what you get when caution wasn't enough.
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Loptr
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Quote: Originally posted by Awesomeness  | Thank you for the input.
@deltaH: The spheres tarnish quickly, as I discovered that oxygen and/or water are very slightly soluble in xylene. Perhaps this would passivate the
sodium enough for transfer to another container. Then again, the passivating effect would have to be even stronger for sodium powder.
@Chemosynthesis: The original procedure stated that shaking the flask for a longer period of time would produce finer sodium. I actually swapped stir
bars halfway through the experiment, but before I did, I saw a few pieces about 2 mm in diameter come off. I might repeat this to see if I can get a
more consistent result.
@Loptr: Mineral oil is indeed a better "solvent" for this preparation. It protects from oxygen better than xylene, and viscosity would decrease anyway
at these temperatures. It also looks like I was a bit optimistic with my "2 grams" of sodium, based on that ethyl acetoacetate preparation.
Here is a video I made of the preparation:
https://www.youtube.com/watch?v=psgVNkBNNUc
[Edited on 3-2-2015 by Awesomeness] |
I dried the xylene with anhydrous magnesium sulfate. There wasn't any noticeable oxidiation, from what I recall.
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careysub
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I wonder if you could deoxygenate the mineral oil/xylene by adding the iron powder from oxygen scavenger packets along with the dehydrating agent.
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blogfast25
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Increase the RPMs drastically to get much finer material, if that's what you're after.
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Loptr
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My problem was that when I cut the heat, but left the stirring on, the sodium was still too hot and all the tiny droplets joined into a massive clump.
I think the toluene idea, where it refluxes just above the MP of sodium, might be a better medium for this. Also, I think the viscosity of the mineral
oil actually played a part in forming larger globules. At elevated temps, it certainly was less viscous, but not enough.
[Edited on 3-2-2015 by Loptr]
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blogfast25
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Personally I think higher viscosity would lead to finer droplets (all other things being equal) because it leads to higher shear stresses and it is
those that 'rip apart' the molten sodium:
http://en.wikipedia.org/wiki/Shear_stress#Shear_stress_in_fl...
[Edited on 4-2-2015 by blogfast25]
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Etaoin Shrdlu
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Generally, it will. Dispersing things finely into a thin fluid is much more of a PITA than into a thick one.
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blogfast25
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That was definitely my experience in the polymer industry: mixtures ('compounds') based on higher viscosity resins tend to be much better mixed, all
other things equal. Higher shear stresses explains that adequately.
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Loptr
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Then I will have to reattempt this with lower temperatures in mineral oil. I think it could be I used too high of a temperature for the mineral oil
bath, which was an attempt to quickly get the sodium into a molten state.
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Etaoin Shrdlu
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| Quote: Originally posted by blogfast25 |
That was definitely my experience in the polymer industry: mixtures ('compounds') based on higher viscosity resins tend to be much better mixed, all
other things equal. Higher shear stresses explains that adequately. |
Same in the coatings industry. Pigment dispersions are generally much higher in viscosity than the final product, otherwise deagglomeration just
doesn't happen at any reasonable speed.
EDIT: I like the milk frother/high shear blade idea, I wonder if it would introduce too much air, though.
[Edited on 2-4-2015 by Etaoin Shrdlu]
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blogfast25
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Yep, too much air I think.
I think I would favour an overhead mixer, blades fairly shallowly positioned in a fairly deep bath of 'solvent'/sodium. Quite high RPM. Crank up RPM
gently from 0 to 'optimal'. Create a large shear gradient.
[Edited on 4-2-2015 by blogfast25]
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subsecret
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Maybe you could use a steel spring instead of a magnetic stir bar to froth the sodium. Steel isn't as hard as glass, but still, scratches could occur.
You could coat the ends of the spring in PTFE.
Fear is what you get when caution wasn't enough.
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j_sum1
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The milk frother is cool. They don't introduce much air if they are submerged deep enough in the liquid. A rbf would actually be perfect for this.
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deltaH
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| Quote: | | My problem was that when I cut the heat, but left the stirring on, the sodium was still too hot and all the tiny droplets joined into a massive clump.
I think the toluene idea, where it refluxes just above the MP of sodium, might be a better medium for this. Also, I think the viscosity of the mineral
oil actually played a part in forming larger globules. At elevated temps, it certainly was less viscous, but not enough. |
The solution to that is to simply quench it by pouring in cold solvent in one go while maintaining stirring, then remove from the hot plate.
[Edited on 4-2-2015 by deltaH]
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m1tanker78
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Try mixing a small quantity of glycol ether (brake fluid) in with your mineral oil and sodium. A while back I demonstrated that doing so renders
molten sodium droplets practically impossible to coalesce except in extreme conditions. I never figured out what took place at the surface but it
would be worth a try. I made some 'sodium sand' this way with a whisk attached to a dremmel. The only way I could get the sodium to coalesce afterward
was to set the oil-drenched sodium droplets on fire in open air until they coalesced then dunked the whole thing back in mineral oil - destroying
whatever surface coating had formed on it.
Chemical CURIOSITY KILLED THE CATalyst.
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Loptr
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| Quote: Originally posted by deltaH | | Quote: | | My problem was that when I cut the heat, but left the stirring on, the sodium was still too hot and all the tiny droplets joined into a massive clump.
I think the toluene idea, where it refluxes just above the MP of sodium, might be a better medium for this. Also, I think the viscosity of the mineral
oil actually played a part in forming larger globules. At elevated temps, it certainly was less viscous, but not enough. |
The solution to that is to simply quench it by pouring in cold solvent in one go while maintaining stirring, then remove from the hot plate.
[Edited on 4-2-2015 by deltaH] |
I thought about this, but didn't know if it could be safely done. I am aware that introducing cool water into very hot conditions can result in a
steam explosion, but I am not sure if mineral oil would react in a similar manner; maybe not an explosion, but blow back, perhaps?
EDIT: Also, now that I think about it, approximately 100C isn't likely to be an issue.
[Edited on 4-2-2015 by Loptr]
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subsecret
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| Quote: Originally posted by Loptr | | Quote: Originally posted by deltaH | | Quote: | | My problem was that when I cut the heat, but left the stirring on, the sodium was still too hot and all the tiny droplets joined into a massive clump.
I think the toluene idea, where it refluxes just above the MP of sodium, might be a better medium for this. Also, I think the viscosity of the mineral
oil actually played a part in forming larger globules. At elevated temps, it certainly was less viscous, but not enough. |
The solution to that is to simply quench it by pouring in cold solvent in one go while maintaining stirring, then remove from the hot plate.
[Edited on 4-2-2015 by deltaH] |
I thought about this, but didn't know if it could be safely done. I am aware that introducing cool water into very hot conditions can result in a
steam explosion, but I am not sure if mineral oil would react in a similar manner; maybe not an explosion, but blow back, perhaps?
EDIT: Also, now that I think about it, approximately 100C isn't likely to be an issue.
[Edited on 4-2-2015 by Loptr] |
Using xylene to cool the flask's contents might cause some flash boiling, but not much.
I forgot to mention this:
While I was distilling starting fluid (ether and heptanes), I added about a gram of sodium to dry the material. It bubbled a little, but nothing
vigorous. A little bit of hydroxide was deposited on the metal. I collected both ether and heptane, leaving only about 5-10 mL of material in the
stillpot. I then noticed that the sodium had coalesced into very shiny spheres, which had a very slight red tint. It seemed to have melted out of the
hydroxide shell that the moisture had caused. Heptane boils at 98.4 degrees, just above sodium's MP. Getting the sodium just above its MP is a good
strategy.
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deltaH
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Sorry, I didn't mention it should be a high boiling solvent... I thought that was kinda obvious though
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Loptr
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| Quote: Originally posted by deltaH | | Sorry, I didn't mention it should be a high boiling solvent... I thought that was kinda obvious though |
Well, I was actually thinking of adding room temperature mineral oil to the hot mineral oil, which is where my statement of ~100C shouldn't be a
problem was coming from because the BP of mineral oil is somewhere around ~310C.
EDIT: Sorry about that too, as I wrote more of a stream of consciousness, rather than explaining my line of thought.
[Edited on 4-2-2015 by Loptr]
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deltaH
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No it's fine, also can serve as a safety warning of sorts. Well spotted.
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