Sciencemadness Discussion Board - Tiny Sodium Spheres

Tiny Sodium Spheres

subsecret - 3-2-2015 at 12:02

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.

deltaH - 3-2-2015 at 12:06

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]

Chemosynthesis - 3-2-2015 at 12:12

Nice post. I wonder if you could try and alter the pellet sizes for bird shot sodium.

Loptr - 3-2-2015 at 12:56

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!

blogfast25 - 3-2-2015 at 13:09

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.

subsecret - 3-2-2015 at 13:15

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]

Loptr - 3-2-2015 at 13:28

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.

careysub - 3-2-2015 at 14:00

I wonder if you could deoxygenate the mineral oil/xylene by adding the iron powder from oxygen scavenger packets along with the dehydrating agent.

blogfast25 - 3-2-2015 at 14:21

Quote: Originally posted by Awesomeness

Here is a video I made of the preparation:
https://www.youtube.com/watch?v=psgVNkBNNUc

Increase the RPMs drastically to get much finer material, if that's what you're after.

Loptr - 3-2-2015 at 14:35

Quote: Originally posted by blogfast25

Quote: Originally posted by Awesomeness

Here is a video I made of the preparation:
https://www.youtube.com/watch?v=psgVNkBNNUc

Increase the RPMs drastically to get much finer material, if that's what you're after.

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]

blogfast25 - 3-2-2015 at 16:24

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]

Etaoin Shrdlu - 3-2-2015 at 17:44

Quote: Originally posted by blogfast25

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]

Generally, it will. Dispersing things finely into a thin fluid is much more of a PITA than into a thick one.

blogfast25 - 3-2-2015 at 17:55

Quote: Originally posted by Etaoin Shrdlu

Generally, it will. Dispersing things finely into a thin fluid is much more of a PITA than into a thick one.

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.

Loptr - 3-2-2015 at 18:07

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.

Etaoin Shrdlu - 3-2-2015 at 18:24

Quote: Originally posted by blogfast25

Quote: Originally posted by Etaoin Shrdlu

Generally, it will. Dispersing things finely into a thin fluid is much more of a PITA than into a thick one.

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]

blogfast25 - 3-2-2015 at 18:45

Quote: Originally posted by Etaoin Shrdlu

EDIT: I like the milk frother/high shear blade idea, I wonder if it would introduce too much air, though.

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]

subsecret - 3-2-2015 at 20:05

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.

j_sum1 - 3-2-2015 at 21:46

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.

deltaH - 3-2-2015 at 22:05

Quote:

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]

m1tanker78 - 3-2-2015 at 22:13

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.

Loptr - 4-2-2015 at 06:40

Quote: Originally posted by deltaH

Quote:

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]

subsecret - 4-2-2015 at 07:48

Quote: Originally posted by Loptr

Quote: Originally posted by deltaH

Quote:

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]

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.

deltaH - 4-2-2015 at 08:54

Sorry, I didn't mention it should be a high boiling solvent... I thought that was kinda obvious though

Loptr - 4-2-2015 at 09:18

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]

deltaH - 4-2-2015 at 09:32

No it's fine, also can serve as a safety warning of sorts. Well spotted.

Loptr - 4-2-2015 at 12:27

Another idea I have had for the production of spherical sodium is as follows.

Take a test tube and drill a few small holes into its closed end, and suspend it over a beaker of room temperature mineral oil. In a beaker, heat sodium until it is in a freely molten state under mineral oil. Once the sodium has been heated to the point where it can easily be poured, start to pour (or pipette) the molten sodium into the first test tube, where the sodium will then proceed to drip through the bottom of the test tube, and into the room-temperature mineral oil.

As the sodium slips through the bottom of the test tube, it will briefly be exposed to air, and will begin to harden and possibly oxidize slightly. Upon contact with the room temperature mineral oil below, it will completely solidify into something resembling a sphere, hopefully. (I think the size of the holes could result in sodium ranging from a sphere to something more elongated, especially if the sodium slips through the bottom as a constant stream.)

I believe the size/shape of the sodium could be controlled by the size of the holes at the bottom of the test tube. Some heating might have to be applied to the test tube in order to keep it as fluid as possible.

I know you guys could provide possible alternatives, so any ideas or issues?

[Edited on 4-2-2015 by Loptr]

S.C. Wack - 4-2-2015 at 18:16

Simply slightly swirling the sodium in hot (not boiling) xylene gives larger shot. A few hard shakes (Fieser, sodium ethoxide) breaks these to dove shot and finer (depends on your definition of tiny), and more shaking reverses that some. References for the preparation of powders and dispersions aren't obscure if you really need them, but most people don't, so the majority don't need to spend more than a few seconds on this.

Loptr - 4-2-2015 at 18:44

Quote: Originally posted by S.C. Wack

Simply slightly swirling the sodium in hot (not boiling) xylene gives larger shot. A few hard shakes (Fieser, sodium ethoxide) breaks these to dove shot and finer (depends on your definition of tiny), and more shaking reverses that some. References for the preparation of powders and dispersions aren't obscure if you really need them, but most people don't, so the majority don't need to spend more than a few seconds on this.

I have a bit of sodium and was considering the possibility of producing sodium sand or spheres, and making it available for purchase here on SM. Similar to the sodium spheres I had for sale here a while back.

So while it might not mean much to the average joe, I would like to produce something with some uniformity in size and shape.

[Edited on 5-2-2015 by Loptr]

subsecret - 4-2-2015 at 18:56

Quote: Originally posted by S.C. Wack

...(Fieser, sodium ethoxide)...

That's the book! Here's the part about the sodium spheres:

About 25 cc. of purified xylene is poured into a 100-cc. round-bottomed,
longnecked flask and 11.5 g. of cleanly cut sodium is quickly weighed
and added. A cork is inserted loosely and the flask is placed in a
sand bath and heated until the rim of boiling xylene rises to the
top of the neck. The flask is removed and wrapped in towels,
the stopper is inserted, and the flask is shaken five or six times
in the direction of its length, giving a sharp whip to each stroke.
A little air is admitted and the mixture is allowed to cool. Too
much shaking often causes the particles to coalesce. In a successful
operation a very finely divided, even powdery, metal
results and it has a bright appearance. Often the product is
more properly described as "bird shot" sodium, and it is rather
gray. If larger lumps are present the heating and shaking should
be repeated.

That's on page 385 of Fieser's Experiments in Organic Chemistry.

[Edited on 5-2-2015 by Awesomeness]

Loptr - 5-2-2015 at 08:49

Here is a book I have stored on Google Drive regarding the preparation of Sodium Amalgam using a procedure similar to the one I provided above. It contains pictures of the sodium amalgam, and it looks nice.

Note on the Preparation of Sodium Amalgam in the Form of Pellets
H. S. Isbell, H. L. Frush, and N. B. Holt (August 26, 1959)

https://drive.google.com/file/d/0B69P61GB16K8V3QzYlBnODZpcmM...

[Edited on 5-2-2015 by Loptr]