Upsilon
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Fluoride "glass"
I have a high interest in theorizing ways to store fluorine gas in a transparent container. It seems pretty well-known here that this can be done with
fused quartz glass with intensive preparation.
Though it is possible, this process is quite difficult to pull off. I read some about fluoride glasses, which are actually a complex mixture of heavy
metal fluorides. I have also found suggestion that they have poor resistance to things even as simple as moisture. But I can find almost no additional
information on the subject, so I'm left to think about it.
My thought is that these heavy metal fluorides may prove useful in storing elemental fluorine gas visibly. They wouldn't necessarily need to be as
robust as lab glassware, but they might at least offer a layer of protection impenetrable to fluorine gas. Perhaps these heavy metal fluorides can be
vitrified into a transparent crystal as silicon dioxide does?
Making a vessel out of fluoride glass alone sounds like a bad idea, so perhaps one could use a fused quartz tube with a custom fluoride glass inner
layer. Obviously it would be extremely tedious to pull all of this off; one would need to find a way to mold the molten fluoride salt into the form of
the inside of the quartz tube. But it just seems possible.
Of course I'm just speculating here and I have not the slightest clue of whether this is actually possible. The molten heavy metal fluoride might
attack the fused quartz quickly enough to cause disaster. Maybe the supposed "moisture sensitivity" of these heavy metal fluorides is significant
enough to warrant total eradication of any water molecules as is necessary for storing fluorine in fused quartz alone. Maybe these heavy metal
fluorides cannot be vitrified. I just don't know. I'd be happy to read through you all's advice on this.
(Mind you, I'm in no way actually trying to do this in real life. If it proves feasible, then MAYBE I will try it in the distant future when it comes
time to add fluorine to my element collection. But don't take this as a gung-ho rush to get this done - that's not why I'm here.)
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j_sum1
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Fluorine has got to be the thorn in the side of every element collector. So tantalisingly close to the top of the table and so darned awkward. I
figured some kind of teflon ampoule was going to be the most likely container if I ever got there. Problem is that teflon is opaque as far as I know.
And it doesn't behave nice like its simple cousin polyethylene. You can't melt and seal.
Another idea worth pursuing is a fluorite ampoule CaF2. Good luck. Although I vaguely recall reading that some fluorite crystals have voids and tiny
pockets of fluorine gas in the voids. Which means that a chunk of said crystal might actually meet the brief. It is going to be at least as good as
any astatine sample.
Of course, for the really serious, you could have a cylinder of nickel with the gas inside. It is not going to be visible, but realistically, what
are you going to see anyway?
This is the best video I have seen of fluorine -- elemental anyway. http://www.periodicvideos.com/videos/009.htm You actually get to see it. I guess, if you were really keen you might be able to organise a liquid
fluorine sample similar to the one shown, seal it (somehow) and embed it in some resin. Again, good luck.
[edit]
forgot to include the link
[Edited on 9-10-2015 by j_sum1]
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UC235
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Quote: Originally posted by j_sum1  | Fluorine has got to be the thorn in the side of every element collector. So tantalisingly close to the top of the table and so darned awkward. I
figured some kind of teflon ampoule was going to be the most likely container if I ever got there. Problem is that teflon is opaque as far as I know.
And it doesn't behave nice like its simple cousin polyethylene. You can't melt and seal.
Another idea worth pursuing is a fluorite ampoule CaF2. Good luck. Although I vaguely recall reading that some fluorite crystals have voids and tiny
pockets of fluorine gas in the voids. Which means that a chunk of said crystal might actually meet the brief. It is going to be at least as good as
any astatine sample.
Of course, for the really serious, you could have a cylinder of nickel with the gas inside. It is not going to be visible, but realistically, what
are you going to see anyway?
This is the best video I have seen of fluorine -- elemental anyway. You actually get to see it. I guess, if you were relly keen you might be able to
organise a liquid fluorine sample similar to the one shown, seal it (somehow) and embed it in some resin. Again, good luck. |
Antozonite (https://en.wikipedia.org/wiki/Antozonite) is what you're thinking of as naturally containing fluorine gas. You could probably make some sort of
ampoule for fluorine out of PFA or FEP which are perfluorinated and melt-castable plastics. They are not completely clear though and are a hazy bluish
color reminiscent of moonstone and for the same reason.
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Upsilon
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j_sum1, are you suggesting that calcium fluoride can be vitrified in a similar manner to silicon dioxide? It would make sense that it could be. It
would probably need to be melted in an arc furnace and poured into a mold, though I don't really know anything about glass casting. This is what I was
thinking when I came across these heavy metal fluorides, though if calcium can work just as well then so be it. Other candidates may be bismuth
trifluoride and zirconium tetrafluoride - the latter is apparently the main component of commercial fluoride glasses. Both have significantly lower
melting points than calcium fluoride and will likely be easier to work with, assuming you can make decent glasses out of them.
UC235, those look pretty promising. Perhaps you could inlay a regular ampoule with a layer of one of these plastics? That way it would be thin enough
to the point of virtual transparency while still having the necessary structural integrity.
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Sulaiman
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mmm .....
fluorine as a supercritical fluid ....
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Boffis
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The problem with a calcium fluoride glass stems from the nature of fluorines monovalency. In a silicate glass there are near infinite chains of
-Si-O-Si-O-Si- etc units. These are relatively stable inspite of the fact that they are thermodynamically metastable and therefore break down and
crystallize into various silica polymorphs and silicates very very slowly, infact silica rich glasses do this only over geological timescales of 10My
to 100My or more.
Fluorine in monovalent and therefore no such chains can form and any "glass" that forms is simply a quenched amorphous phase and is highly metastable.
The lack of chain which need to be broken down means that this type of glass tends to crystallize quickly, you can try this with the plastic sulphur
experiment. The addition of other metal fluorides may retard this process but I wouldn't want to bank on their long term structural integrity when
they are confining something like fluorine. The best you can hope to achieve would perhaps be a glass with a siloxy -Si-O-Si- backbone on which the
lateral bonds are to fluorines but I think that this material would be rather prone to hydrolysis by moisture and the lack of lateral cross linking
would make the glass exceedingly fragile.
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j_sum1
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Good thinking Boffis.
So, we are back to replacing the OH on the surface of the glass with F as per this link and working with teflon.
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BromicAcid
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Early work, including Moissan's original apparatus for preparing fluorine had fluorite as key components. In Moissan's case the u-tube in which his
electrolysis occurred had calcium fluoride stoppers coated in shellac. Not sure if the shellac was to increase durability, seal the stoppers to the
setup, or some combination thereof.
Not a glass but note that PFA has a rating of 'recommended' for fluorine up to 60C, PFA unlike Teflon can be purchased as clear tubing, although, like
Teflon it resists being heat-sealed.
[Edited on 10/10/2015 by BromicAcid]
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Upsilon
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It's looking like the PFA method would be more practical then. It's not as clear as I would like, however. Obviously the thinner it is, the greater
the transparency, but it would likely be far too fragile if it was thin enough to be comparably transparent to glass. Maybe you could melt down some
PFA and apply a thin coat to the inside of a regular glass tube?
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