Any fluorine experts here?

[jdurg]

A lot of us here know that fluorine is incredibly reactive and amazingly toxic. I'm just wondering if there's anybody here who works with the pure element and/or knows a ton about it? The reason I ask is because I've come up with a way to generate the pure element that I think may work.

 

You would start off by taking a standard glass tube that is maybe a foot long and heating the bejesus out of it. This would be to keep any and all water out of the tube, and to burn out any loose chemicals in the tube. It would basically be sterlizing and cleaning the tube with a ton of heat. (Basically heating the glass a small bit below it's melting point. You would then go and let the glass tube dry in an argon dry box with some anhydrous sodium silicate or cobalt chloride in there to absorb any random water molecules. With the tube cooled, and sealed fully at one end, you would then put a good bit of 100% anhydrous CaF2 in the tube. At this point, you'd pull a vacuum on the tube and remove any and all gas that is inside there. The tube would then be sealed off at the top. Now, you'd take the CaF2 end and put it in a high temperature flame. Not high enough to melt the glass, but high enough to decompose the fluoride salt into a tiny bit of fluorine gas. Due to the heat and the vacuum, the gas would then rise to the top of the tube. You would continue to do this until you could see the tiny, faint color of fluorine up at the top. At this point, you would quickly move the flame up to the middle of the tubing and seal off the tubing below the fluorine gas. You would now have an ampoule of pure fluorine gas.

 

Since fluorine doesn't eat glass (HF does), it should remain pretty stable in there for quite some time. My only questions are #1, will this work?, and #2, how much fluorine is generated by the decomposition of CaF2? I've heard that the fluoride salt will decompose into fluorine gas, but I just don't know at what rate it will do that, and at what temperature.

[raivo]

As much as i know CaF2 will not decompose by heating. It melts at 1418 C and should boil somewhere near to 2500 C.

 

I have thought of making some fluorine or fluorides using teflon as source because it decomposes easyli at rather low temperatures. In normal conditions, when decomposing, it reacts with water and oxygen and makes some deadly gases but it may still be possible to get something useful of it. ( This is just an idea. )

[jdurg]

Hmm. Perhaps then I should see about getting this done with teflon powder. The only reason I was thinking about CaF2 is that when reading the MSDS for it, it stated that it will decompose under elevated temperatures into some rather nasty gasses. (And the only gas I can think of is fluorine gas).

[budullewraagh]

actually, at those temperatures you may just oxidize oxygen with fluorine...so i'd heat it in an atmosphere of either helium or argon, but preferrably helium

[jdurg]

Well, the plan is to completely dry out the tube through extensive heating which would be done in a completely inert atmosphere. The tube would then be sealed off at both ends with a vacuum contained within the tube, along with the fluorine generation source. (Either a fluoride salt or teflon as mentioned above). This way, there is no worry about any gasses inside the tube reacting with the fluorine, and very little, if any, chance of water being in there. Also, by having a vacuum in there the gas, as it's generated, will be more likely to rise up to the top section of the tube which is what we would want. The more I think about it, the more viable this seems. Hmmmmmm.........

[Gilded]

"Since fluorine doesn't eat glass (HF does)"

 

That's true, however:

 

Normal bonds in a quartz glass tube: Si-O-Si bonds

Rare, yet unavoidable in a quartz glass tube: Si-OH ends

Guess if the fluorine forms HF with Mr. H there?

 

And even if there are only a few H2O molecules in the tube, the HF will form and destroy the tube (very, very slowly though)

[raivo]

Possible decomposition of CaF2 my occur if it gets in contact with anything acidic especially in high temperatures. Normal environment contains always some acids. I think this is the thing those MSDS talk about but i am not sure.

 

Teflon surely will decompose by heating but this probably is not the thing to play with. It may be fairly safe if decomposition products get instantly in contact with something they can react with. But otherwise it is very dangerous.

 

Elemental fluorine can be made by electrolysis of molten mixture of KF and nonaqueous HF at 70...100 C. HF can be made by heating concentrated H2SO4 and CaF2 in led (!) retort.

 

This all seems too dangerous and complicated to play with (although interesting to talk about.)

[Gilded]

"This all seems too dangerous and complicated to play with (although interesting to talk about.)"

 

As fluorine is the most electronegative element, it's not too fun to play with. Platinum happens to be one of the few elements it doesn't react with.