raven
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sodium metal sample
hello to all of you,this is my first post on this forum so please bare with me.i recently aquired a sample of sodium metal.that was a beautiful silver
colour with no signs of contamination or decay.now just a few weeks on the edges and corners have started turning a brown/gold colour with lots of
fluff or hairs ,so much so that its began to settle of the bottom of the container ,could this be sodium peroxide forming i think its normal for a
white hydroxide to appear after a while unless completely sealed so no oxygen can get in,but i thought it was difficult for peroxides to appear .i
know that potassium developes super oxides /peroxides readily .any how any suggestions to what this could be and how to deal with it, is it avisable
to try and cut these edges off,it seems to be growing quite quickly all over the exterior of the samples
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Maya
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we don't know how you are storing them....
Thats usually the key, but if you store in liquids , the results can vary widely b/c of purity of liquid.
for instance, I have 2X 7 pound sticks which I have stored in plastic baggies. no further oxidation past a certain point since no O2 or water can get
to it. over a year now and still good.
some hydrocarbons have funky stuff in them so that can cause further reactions sometimes
\"Prefiero ser yo extranjero en otras patrias, a serlo en la mia\"
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raven
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yes thats a good point ,there stored under a clear oil ,im not sure what type of oil ,it came like it.it,s a 50 gram sample in a clear plastic screw
top container .i dont suppose thats much help.
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woelen
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Put it in a glass container, with a metal screw cap. Some plastics are porous and allow oxygen to slowly pass through them. Use the same oil, as the
oil, in which it is stored now. That oil by now is free of oxygen and humidity. If you use fresh oil, then almost certainly, again a small amount of
the sodium is oxidized.
And yes, sodium can form peroxides. I also have some sodium, and it has yellow/orange spots on its surface, which quickly disappear when brought in
contact with water.
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Fleaker
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I Saran wrap my bricks then double bag them and seal with this plastic heat-sealer. Still look like the day I got them.
Neither flask nor beaker.
"Kid, you don't even know just what you don't know. "
--The Dark Lord Sauron
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chemrox
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Fleaker-walk me through that one in a p2p please.
I was getting rerady to move mine from plastic to glass. I had some Na and some K I got from a school and the stuff was under kerosene but died in a
cooler in the garage. Slow steady infiltration of O2.
"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
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raven
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i think i will be putting mine into a glass screw top container ,then placed into a rubbermaid jar ,the ones with the rubber seal.hopefully that will
be air tight.i was thinking of removing the brown oxides/peroxides with a knife ,just trim them off.this should be ok aslong as i handle it with the
respect that sodium metal requires
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chemrox
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Unless you plan to wrap it up as Fleaker does of seal it in wax, leave the oxide coating on. Otherwise a new coating will form anyway and you're out
the trimmings.
"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
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-jeffB
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| Quote: | Originally posted by Fleaker
I Saran wrap my bricks then double bag them and seal with this plastic heat-sealer. Still look like the day I got them. |
Say, is this contemporary Saran Wrap -- the kind that's just as oxygen-permeable as all the other polyethylene formulations -- or old-school PVDC
Saran Wrap, the kind with lots of carbon-bound chlorine that's probably not very well-behaved in contact with an alkali metal? 
On a related topic, does anybody in the US know of a way to get original PVDC Saran? Dow decided to help us all out by removing the insidious, deadly
chlorine, thereby also removing the only really good oxygen-excluding plastic wrap on the market...
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Fleaker
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It's actually Glad Cling wrap, but it's the same composition. How oxygen-permeable is it? Numbers, references, or personal experience? I think these
bricks are 10 months old and they look fine to me. But it could be all the other redundant packaging, perhaps?
AS far as PVDC being well behaved, it probably would be, unless you melt your sodium when you store it? Surface area, right?
Neither flask nor beaker.
"Kid, you don't even know just what you don't know. "
--The Dark Lord Sauron
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-jeffB
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| Quote: | Originally posted by Fleaker
It's actually Glad Cling wrap, but it's the same composition. How oxygen-permeable is it? Numbers, references, or personal experience? I think these
bricks are 10 months old and they look fine to me. But it could be all the other redundant packaging, perhaps?
AS far as PVDC being well behaved, it probably would be, unless you melt your sodium when you store it? Surface area, right? |
I don't have the numbers on hand, but the figure I remember is something like a factor of 100 -- "real" Saran Wrap was about 100 times less
oxygen-permeable than the new crap.
I don't know about the compatibility issue for sure. I just took note of the warnings against putting sodium in contact with chlorinated solvents
(CCl4, etc.), and generalized. If you've got sodium wrapped in PVDC and haven't had trouble, perhaps your experimental observation trumps my nervous
speculation -- or perhaps you've just been lucky so far?
Edit: Or maybe I could just read the part where you said you're using Glad Cling Wrap, which is polyethylene, and thus poses no compatibility risk.
Time for bed here, apparently.
[Edited on 12-14-07 by -jeffB]
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