chemrox - 20-10-2008 at 13:22
I'm trying to make birdshot sodium by melting the Na in xylene. The xylene is boiling and the Na didn't melt. It was supposed to melt at around
96*C. The Na was quite fresh and the cutting up made lots surface. Any experience doing this that could help?
Thanks,
CRX
garage chemist - 20-10-2008 at 13:42
The sodium did melt. You just didn't see it.
Heat it again, stopper and shake the flask (with gloves of course) and you'll see what I mean.
panziandi - 20-10-2008 at 14:10
Indeed the sodium will melt but it will remain in the same shape as when it was solid! You must agitate the flask to break it up! Heat the xylene it
doesn't need to boil, stopper and remove from the heat. Shake the flask as vigorously as possible until it cools enough for the sodium to solidify.
The harder and faster the shaking, the finer the sodium powder obtained. I have obtained various sized particulates from this method. Also have
prepared NaK by melting potassium and sodium under xylenes.
storage
chemrox - 20-10-2008 at 14:49
Nevermind-false alarm.. I just needed to heat it longer..it melted and turned into birdshot on shaking. Now I have a bunch of surface area. How long
can I store it under xylene?
[Edited on 21-10-2008 by chemrox]
panziandi - 21-10-2008 at 13:06
Not terribly long since xylene will wet which will obviously lead to reaction with sodium and it'll be bad. I can't give a length of time exactly
however. I make my shot under liquid paraffin (from chemist) I dry it by heating above 100*C then I add clean sodium stopper and shake the molten
sodium until its solid and fine. This is more stable since liquid paraffin wets less. In addition i bottle and store under argon. You can wash the
sodium free of paraffin with dry toluene under argon using standard manipulation on a manifold. Are you familiar with these techniques? In addition
you can wash with pentane and pull a vacuum which gives you dry (i.e. solvent free sodium powder).
chemrox - 21-10-2008 at 21:53
"You can wash the sodium free of paraffin with dry toluene under argon using standard manipulation on a manifold. Are you familiar with these
techniques?" No, please detail it for us (me).
panziandi - 22-10-2008 at 12:02
Sure! Basically you want to obtain a two-necked flask and dual manifold (vacuum and inert gas). Weigh out your dispersion into the flask (take into
account the oil and the % weight of Na) then attach to the manifold on one neck and to the other add a septum. Purge the flask with vacuum and inert
gas on repeat to replace the full volume of the head space in teh flask with inert gas. Syringe in dry petroleum ether, swirl to mix, allow Na to
settle, remove petroleum with a syringe. Then repeat the washings several times more, then pull a vacuum on the flask to remove traces of the
petroleum ether. Then you can weight the change in weight and calculate the exact mass of Na in the flask. Also you can then add the appropriate
solvent for the reaction, be it an ether, hydrocarbon or whatever.
There are other methods too. If you don't have a manifold do not dispair! You can use a standard round bottom flask with septum over the neck, use a
hypodermic needle connected to inert gas (Ar welding gas) and a hypodermic needle to vent to atmosphere etc, then syringe in the petroleum through a
third needle. If you have a very fine Na dispersion it is even possible to wash in one flask, resuspend and then transfer to another flask via cannula
and +ve pressure. Would you like me to do some sketches?
Klute - 23-10-2008 at 03:29
I woul dsuggest using a inflatable ballon for such washing instead of a current of argon, as it will compensate the volume of solvent added (and the
little H2 that nearly always forms from the traces of water in the solvent), with minimal exposure to atmospher and little waste of argon.
Indeed, schlenks and a manifold are not absolutle necessary to perform such work, you can always work your way out with gas inlet with taps, and a
seperate sourc eof vacuum and inert gas. Obviously it isn't as good as with a manifold, but if you are working on anionic polymerisations or very
oxygen-sensible compounds, you should be properly equipped 
DrP - 23-10-2008 at 03:33
Excuse my ignorance chemrox, but what is 'birdshot' sodium? I have this image of loading a shotgun cartridge with sodium shot. That would be well
nasty if you were shot with that!! Bloody hell!
Picric-A - 23-10-2008 at 05:00
I havnt heard of the term Birdshot Sodium before but i recognise the method they use to make it.
It is basically Powdered sodium.
12AX7 - 23-10-2008 at 09:11
It would have an awesome muzzle flash. A pain to clean the barrel though.
http://periodictable.com/PopSci/2005/04/1/index.html
Tim
DrP - 23-10-2008 at 09:19
Couldn't you coat them in lead or something to protect them until impact? Then you'd get the sodium - blood reaction when the casing split....
Nasty!?
chemrox - 23-10-2008 at 12:01
One could load a sabot with birdshot sodium and put it into a shotgun shell. Much nastier than rock salt. @Picric- I beg to differ, this is not the
same as powdered Na .. not nearly as much surface area and its called "birdshot" because it forms small spheres.. the more you shake it the smaller
the shot. I think you use a different liquid if you want to powder it.. starting with shot (?).
panziandi - 23-10-2008 at 12:37
It takes a bit of skill or time experimenting to find the correct way to get the suitable sized particles. I have obtained quite varied sizes form the
heavy paraffin (medicinal paraffin) by shaking differently etc. I found this the safest method too, since there is no chance of a vapour fire,
refluxing xylene carefully around the neck of the flask is fine but I didn't fancy the method. Now I'm very keen with my paraffin method. Easily
washed with petroleum ether. Dry all solvents with sodium first or else they will react with the sodium powder... obvious but may slip some peoples
minds! And another obvious point but finely divided sodium is dreadfully flammable! I think "sodium grit" "sodium powder" and "birdshot sodium" sodium
are fairly interchangeable and open for a degree of user interpretation.
zed - 23-10-2008 at 16:12
Paraffin Oil, or as we call it in the U.S..... mineral oil, is a great material for protecting Alkali metals from air and moisture.
At least one major U.S. manufacturer of Lithium Aluminum Hydride, used to supply it as a heavy paste, blended with mineral oil.
Much safer to handle such materials when they are coated with mineral oil. And often, the coated Alkali metal or Hydride, can be used as is. The
residual mineral oil can be easily removed from desired reaction products during workup.
panziandi - 24-10-2008 at 13:11
Indeed but sometimes when you want an exact weight of metal or hydride it is necessary to remove the paraffin in a pre-weighed flask by washing and
vac-down. What if your product is a high boiling hydrophobic chemical? SOmetimes replacing the paraffin has its benefits. The oil I use is quite
viscous BP grade material.