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sbreheny
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[*] posted on 23-10-2014 at 05:29
Fluorine in quartz?


Hi all,

There is a seller from the Netherlands on eBay who claims to be selling quartz ampoules containing a mixture of 67% He and 33% F:

http://www.ebay.com/itm/141404701586

Of course, fluorine is notoriously difficult to store in any kind of transparent container. Is it true that a diluted mixture with Helium like this will not attack quartz?

My Google research so far indicates that mixtures like this are used in excimer lasers, but I couldn't find details about the envelope which contains such a mixture inside an excimer laser and whether it is quartz.

Sean
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Amos
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[*] posted on 23-10-2014 at 06:11


As far as I've been told, fluorine attacks and combusts SiO2...



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UnintentionalChaos
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[*] posted on 23-10-2014 at 06:29


Low pressure F2 mixed with He in what is probably annealed quartz has a reasonable lifetime as an element sample. How long exactly, I don't know, but it's prevalent enough that I've heard of it before.



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[*] posted on 23-10-2014 at 06:35


There are ways to even further extend the lifespan of the ampoule, but yes, this person is most likely legitimate.



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sbreheny
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[*] posted on 23-10-2014 at 06:36


Quote: Originally posted by No Tears Only Dreams Now  
As far as I've been told, fluorine attacks and combusts SiO2...


Thanks for your reply. I don't think it combusts (maybe finely divided SiO2 would) but rather I think it etches it, until the F2 has all reacted or the SiO2 is etched all the way through and the remaining F2 leaks out.

However, that's what happens with full-strength F2. Maybe if diluted sufficiently with an inert gas, the rate of reaction with the SiO2 is drastically reduced?

I am in the process of making two full (as full as possible) periodic table element sets and I purchased two of these ampoules. I am looking for information about whether this is plausible or likely a scam. I have not received the ampoules yet. Anyone think of any way to test whether there is F2 inside?

The only way I can think to do it would be to put the ampoule inside a larger vessel, along with something that F2 reacts very vigorously with (but other gasses do not so violently react with - like maybe lithium metal or even iron filings), and break the ampoule inside the larger vessel and watch for the reaction. Of course, this would have to be done in a good hood for safety in case the outer vessel broke or leaked. There should be enough metal inside to completely react with the F2 and sequester it. This is, unfortunately, an expensive and destructive test, though.

Sean
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Dan Vizine
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[*] posted on 23-10-2014 at 07:49


If the F2 is free of trace HF, then quartz can have a lifetime of years before becoming cloudy, especially if the F2 is diluted. Over time, the F2 will abstract hydrogen from the inevitable residual Si-OH species and make the HF. The best samples have ampoules that have had the Si-OHs end-capped.

Absorption spectroscopy could confirm it non-destructively. It simply shines light through the sample and looks for what's missing when it comes out.
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[*] posted on 23-10-2014 at 10:34


@sbreheny: if you only have amateur equipment your idea of destroying the ampoule is probably the only way to check for fluorine. I bet that you will not detect any fluorine. I don't believe in these "fluorine helium ampoules". If you want to detect it, it is not very logical to take something which will produce a "violent" reaction. You have to find something that will only produce a positive reaction with fluorine, somethin specific. Lithium is the exact opposite of that.

Quartz is not a suitable container for elemental fluorine. A tiny amount (some molecules) of water will act as a catalyst an destroy your fluorine after a while. The only transparent material to store fluorine for centuries are fluorides, e.g. CaF2.
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[*] posted on 23-10-2014 at 12:21


Theo Gray has a good description of what you need to do to get a long lasting F2 sample in quartz. It's an easy search. Nothing on He dilution and I am dubious.

I am surprised that no one seems to be attempting displays of F2 in PTFE. It seems an obvious choice.
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[*] posted on 23-10-2014 at 12:21


I feel obliged to link to Theodore Grey's periodic table webpage entry on fluorine, where he describes actual pure fluorine in quartz and the difficulty in preparing such a container:
http://theodoregray.com/periodictable/Elements/009/index.s7....

Scroll down to "Real visible fluorine." I'll also quote it here for posterity.
Quote:
Now, respectfully, I must take up a little bit of a qualm with your claim in fluorine...You mention that "There is no transparent container that will hold it." Granted that is true if you're talking a "forever" time scale, but I strongly believe on a "realistic" scale (a few decades) it can be done...albeit with some difficulty and great time placed into it. The way best to do it is first to get yourself a pure, single-crystal quartz tube...Now that means one with an extremely high amount of surface Si-O-Si bonds and VERY few Si-OH endcaps. The best way to do this is to take the inside portion of the quartz tube and silylate it. Then anneal it at the highest possible temperature that your annealing oven can stand...This will drive off essentially ALLLLLLL the Si-OH end caps. Because remember, the real killer in fluorine gas for Si-O's is not the fluorine, but the OH's and their ability to start a chain reaction with small amounts of HF in the fluorine gas. So, the first thing you need to do is get rid of the Si-OH's which that should take care of as best as possible. Now, being absolutely certain that your quartz tube is flamed and ultra-dry, there's another step...There was a fluorocarbon grease that DuPont made many years ago that was ultra-high-purity completely fluorinated, medium-high mol.weight fluorocarbon grease (like a lower-molecular weight Teflon)...Take that stuff and literally melt it into the tube...It's clear and translucent and won't affect the optics after the next step...So then take a high temperature vacuum oven and turn the tube upside down and melt the grease back out...What this does is leave a verrrrry thin, essentially invisible layer of fluorocarbon grease layer on the inside of the tube. This layer acts as a secondary "buffer" layer to the quartz. So IF there are any Si-OH's left on your quartz, they are difficult to get at by the fluorine gas because the fluorine gas has a difficult time penetrating the grease...This step will add years to your fluorine gas display. Then the more difficult thing to do is to make sure the quartz tube has a high-purity Teflon screw-top stopper to it so that it can seal ultra-tightly. (again, pure fluorine gas without any water/HF in it may "trade" fluorines with Teflon, but you still have Teflon; same goes for the grease, the grease may "trade" fluorines as we've seen in some isotopic studies, but it remains a carbon-fluorine bond).
Then you should get a sacrificial vacuum line (kind of expensive, but it'll just be fogged up after you're done though it's best to throw it away because the integrity will be damaged) and run your fluorine gas THROUGH A LIQUID NITROGEN FILLED TRAP into your evacuated quartz tube. This is the most important AND DANGEROUS step. This step is the most important because ALLLLL commercial fluorine sources have either water or HF in them. The water and HF are what will start the "chain reaction" of eating away at things. And all it takes are a few atoms of these to get it started...But the N2(l) will definitely remove ALL of them...But the fluorine gas will still have a small amount of volatility to it so as to fill your quartz tube with approximately a quarter-atmosphere of pure F2. Now if you do anything with fluorine and leave ANY HF or H2O in it, fuggetaboutit...You'll get your stuff eaten away promptly. You won't get a full atmosphere of fluorine in your quartz sample tube like I said, but it will be enough to see under the right light and circumstances. And 50 years from now those one or two atoms of HF and H2O that are left in there will eventually have done enough damage to destroy your sample tube, but I don't plan on worrying about it 50 years from now.
Sorry if that bored you...But I do say it with utmost respect...I spent 10 years fiddling and trying to perfect the best way to get a fluorine sample, and that's the best way I could get it...So, methinks there are ways to store fluorine safely in a visible specimen tube; it just takes a great amount of patience, diligence, safety-thoughts and equipment.
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Dan Vizine
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[*] posted on 23-10-2014 at 12:47


Fluorine eats PTFE, it's only happy when all the carbon is CF4.

The ampoules that I last saw that were prepared in the Ted Grey way were $600 each.

[Edited on 23-10-2014 by Dan Vizine]
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[*] posted on 23-10-2014 at 13:05


This is how you can store fluorine gas in a container, and still look at it:
put it in a nickel tube which is capped by a CaF2 window (like these) on each side.

Of course, the gas is introduced through the nickel tube wall, which is then sealed shut.


By the way, I don't understand why would anybody want to possess such an ampoule. 30% fluorine gas? What for?

[Edited on 23-10-2014 by DrMario]
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[*] posted on 23-10-2014 at 13:14


Quote: Originally posted by Dan Vizine  
The ampoules that I last saw that were prepared in the Ted Grey way were $600 each.



He's a great guy but not much of an authority on anything.




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[*] posted on 23-10-2014 at 13:19


Quote: Originally posted by DrMario  
This is how you can store fluorine gas in a container, and still look at it:
put it in a nickel tube which is capped by a CaF2 window (like these) on each side.

Of course, the gas is introduced through the nickel tube wall, which is then sealed shut.


By the way, I don't understand why would anybody want to possess such an ampoule. 30% fluorine gas? What for?

[Edited on 23-10-2014 by DrMario]


Having an ampoule of 30% Fluorine is a mean in itself. It's for the element collector as a Kilo of cocaine is for the drug addict ;)
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Dan Vizine
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[*] posted on 23-10-2014 at 13:20


Quote: Originally posted by DrMario  


By the way, I don't understand why would anybody want to possess such an ampoule. 30% fluorine gas? What for?

[Edited on 23-10-2014 by DrMario]


Really? You've never run across an element collector?

I've got one. Makes me feel complete....
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DrMario
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[*] posted on 23-10-2014 at 13:21


I can completely see the point of 1 Kg of cocaine for the druggie. I've never tried it, but I hear cocaine is lots of fun, when consumed.

Fluorine, on the other hand, is probably not much fun when consumed :D

No comments on my method? It should be able to store 100% fluorine gas, indefinitely, making said "element collector" very happy. And yet, no signs of happiness anywhere.
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HgDinis25
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[*] posted on 23-10-2014 at 13:24


Quote: Originally posted by DrMario  
I can completely see the point of 1 Kg of cocaine for the druggie. I've never tried it, but I hear cocaine is lots of fun, when consumed.

Fluorine, on the other hand, is probably not much fun when consumed :D

No comments on my method? It should be able to store 100% fluorine gas, indefinitely, making said "element collector" very happy. And yet, no signs of happiness anywhere.


hahahaha
Usually the biggest problem is actualy getting the Fluorine...
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DrMario
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[*] posted on 23-10-2014 at 13:39


Quote: Originally posted by sbreheny  
Hi all,

There is a seller from the Netherlands on eBay who claims to be selling quartz ampoules containing a mixture of 67% He and 33% F:

http://www.ebay.com/itm/141404701586

Of course, fluorine is notoriously difficult to store in any kind of transparent container. Is it true that a diluted mixture with Helium like this will not attack quartz?

My Google research so far indicates that mixtures like this are used in excimer lasers, but I couldn't find details about the envelope which contains such a mixture inside an excimer laser and whether it is quartz.

Sean


Here are a few random comments: the seller doesn't even mention the amount of fluorine/the volume of the ampoule/the partial pressures of the gases. You would think he/she could be arsed to put that in the eBay description, for a whopping $90!

How 'bout this: I'll seal an ampoule and tell you it contains 33% fluorine, for the low price of $40.
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HgDinis25
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[*] posted on 23-10-2014 at 13:44


Quote: Originally posted by DrMario  
Quote: Originally posted by sbreheny  
Hi all,

There is a seller from the Netherlands on eBay who claims to be selling quartz ampoules containing a mixture of 67% He and 33% F:

http://www.ebay.com/itm/141404701586

Of course, fluorine is notoriously difficult to store in any kind of transparent container. Is it true that a diluted mixture with Helium like this will not attack quartz?

My Google research so far indicates that mixtures like this are used in excimer lasers, but I couldn't find details about the envelope which contains such a mixture inside an excimer laser and whether it is quartz.

Sean


Here are a few random comments: the seller doesn't even mention the amount of fluorine/the volume of the ampoule/the partial pressures of the gases. You would think he/she could be arsed to put that in the eBay description, for a whopping $90!

How 'bout this: I'll seal an ampoule and tell you it contains 33% fluorine, for the low price of $40.


Then some mad chemist is going to take some refraction index measurments using top of the line, 10 digits past the coma, equipment. All to confirm some air is present. At least the quartz ampoule is usefull...
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[*] posted on 23-10-2014 at 13:51


Actually, I've talked with the sellers, Stefan and Chantal ( I think), anyway they were interested in buying F2 from me when I was entertaining the thought of building a F2 generator. So, for what it's worth, I believe that they are probably legit.
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[*] posted on 23-10-2014 at 13:57


Quote: Originally posted by HgDinis25  
At least the quartz ampoule is usefull...


Not for long, if it's filled with fluorine gas :P

BTW, to determine fluorine gas, you only need a UV absorption spectrometer. Not too exotic, unless the money was all spent on building the element collection. And we all know how bitchin' expensive that astatine is...
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[*] posted on 23-10-2014 at 14:08


Quote: Originally posted by DrMario  
Quote: Originally posted by HgDinis25  
At least the quartz ampoule is usefull...


Not for long, if it's filled with fluorine gas :P

BTW, to determine fluorine gas, you only need a UV absorption spectrometer. Not too exotic, unless the money was all spent on building the element collection. And we all know how bitchin' expensive that astatine is...


There's no problem, I got my astatine for free when buying more than 10 grams of Darmstadtium...

Ontopic: Another way to have Fluorine is to buy a mineral (I've forgotten the name/I'll try to find it later) that has elemental Fluorine gas inprisioned inside the crystal structure. They discovered it because the miners we're always complaining abou a strange smell whenever they broke a pice of the mineral.
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DrMario
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[*] posted on 23-10-2014 at 14:11


Quote: Originally posted by HgDinis25  

Ontopic: Another way to have Fluorine is to buy a mineral (I've forgotten the name/I'll try to find it later) that has elemental Fluorine gas inprisioned inside the crystal structure. They discovered it because the miners we're always complaining abou a strange smell whenever they broke a pice of the mineral.


That would be fluorite, CaF2 (which, BTW, I mentioned earlier).
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[*] posted on 23-10-2014 at 14:14


Quote: Originally posted by HgDinis25  
Quote: Originally posted by DrMario  
Quote: Originally posted by HgDinis25  
At least the quartz ampoule is usefull...


Not for long, if it's filled with fluorine gas :P

BTW, to determine fluorine gas, you only need a UV absorption spectrometer. Not too exotic, unless the money was all spent on building the element collection. And we all know how bitchin' expensive that astatine is...


There's no problem, I got my astatine for free when buying more than 10 grams of Darmstadtium...

Ontopic: Another way to have Fluorine is to buy a mineral (I've forgotten the name/I'll try to find it later) that has elemental Fluorine gas inprisioned inside the crystal structure. They discovered it because the miners we're always complaining abou a strange smell whenever they broke a pice of the mineral.


It's called fetid fluorite or Antozonite. Irradiation of the calcium fluoride by decaying uranium causes small inclusions of fluorine gas to form.




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[*] posted on 23-10-2014 at 20:32


Quote: Originally posted by DrMario  
I can completely see the point of 1 Kg of cocaine for the druggie. I've never tried it, but I hear cocaine is lots of fun, when consumed.

Fluorine, on the other hand, is probably not much fun when consumed :D

No comments on my method? It should be able to store 100% fluorine gas, indefinitely, making said "element collector" very happy. And yet, no signs of happiness anywhere.


I do have a comment. It won't work because you have no way to make gas tight seals between the salt and the metal tube that won't be attacked by the halogen.
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[*] posted on 23-10-2014 at 21:21


Quote: Originally posted by Dan Vizine  


...It won't work because you have no way to make gas tight seals between the salt and the metal tube that won't be attacked by the halogen.


What about an o-ring made of teflon or another fluorinated polymer?

Even the idea of creating a direct bond between the Ni and the CaF2 isn't so inconceivable because the nickel withstands attack by F2 by the formation of a NiF2 passivation coating on contact. That layer could be affixed to the the CaF2 using a lower melting fluoride salt as a "solder".

*edited to remove typo*

[Edited on 2014-10-24 by Arcuritech]




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