I heated reaction result of NaOH + Mg which contains Na metal under lamp oil to 200-300C in a borosilicate beaker wo allow coalescing the Na droplets.
The lamp oil catched fire so I extinguished it. Then I let the (sooted) beaker cool, threw the Na-containing slurry into al glass jar under oil and
closed the jar. And i kept water welll away !!
Wonder that the Na metal did not catch fire (it was covered by the oil).
Now I cleaned the beaker with scrubbing pads which succeeded but some gray/white blurring left. The beaker is useable, but I am curious whether the
(hot) Na metal attacked the glass.
zoombafu - 10-1-2012 at 14:54
Was the glass cleaned and dried very well before using? I know that when you are running an anhydrous reaction you have to clean your glassware with
acetone, which will dry it, and you can also cook it in an oven overnight to remove any remaining water. Try doing this then re-run the reaction.Sublimatus - 10-1-2012 at 14:57
I know sodium hydride attacks borosilicate to give sodium borohydride.BromicAcid - 10-1-2012 at 15:02
I know sodium hydride attacks borosilicate to give sodium borohydride.
Actually it mainly gives sodium silicate, if it made sodium borohydride there would be a lot of happy chemists out there. But still, I would also
suspect sodium hydroxide (unreacted starter) being the culprit over sodium metal. IIRC only lithium metal attacks borosilicate glass.
Edit: Read too fast, thought it read sodium hydroxide since there wasn't anything on sodium hydride in the first post.
[Edited on 1/11/2012 by BromicAcid]m1tanker78 - 10-1-2012 at 15:09
Yes, in my experience molten sodium attacks all common glasses (including boro). At best, the glass becomes frosted. Use stainless steel for best
results when heating sodium (under oil) for coalescing or whatever.
If I were you, I wouldn't trust that beaker for heating/cooling anything any longer.
Tankbahamuth - 10-1-2012 at 16:52
On that picture, to me it looks like metal residue of some sorts, maybe incorporated into the glass matric somehow. Though it might just be the
picture and since I know Simax produce good glassware (atleast beakers) it might just be me being blind...
Sodium might have reacted with the moisture in the glass to give NaOH and just etch it a little bit.
Other posibilities could be Mg deposits or similar.
NaBH4 is indeed made by reacting NaH with a borosilicate glass, but under Hydrogen pressure and at elevated temperatures. Lots of litterature on the
net on that.
And I wouldn't be worried about using the beaker as I have used beakers and flasks with heavy grindmarks after an overnight stirring with a magnet and
some hard insoluble particles. The glass is made to be used and as long there isn't any extreme pits I wouldn't worry. Clean it with aqua regia and
heat somewhat to get it going, and it should be good as new, except for a couple etched spots. Even the lab glassware dishwasher at the lab used to
grind the insides of the glassware due to ignorant people putting the flasks and beakers onto to-long nozzles.Endimion17 - 10-1-2012 at 18:19
I was melting sodium for several times under kerosene and nothing ever happened. The point is to avoid excessive heating, obviously. Sodium melts at
around 98 °C, so going over 120-130 is an overkill,. Plus the kerosene starts to fume, leading to headache.
If you keep the temperature low enough, kerosene or any similar inert organic liquid will stay viscous enough to prevent the metal from actually
touching the glass, and the metal's reactivity is less obvious.
