blogfast25
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Fusion of Fluorite with soda...
Fusion of Fluorite with soda...
Acc. Holleman, NaF can be made by fusing soda and Fluorite:
CaF2 + Na2CO3 ---> CaCO3 + 2 NaF
The relatively lowly water soluble NaF (4.13 g / 100 g, Wiki) could then be leached out from the frit.
Alternatively maybe NaOH could be used:
CaF2 + 2 NaOH ---> Ca(OH)2 + 2 NaF
then treat the crushed frit with soda, so that
Ca(OH)2 + Na2CO3 ---> CaCO3 + 2 NaOH
Using the huge difference in solubility between NaOH and NaF the two could the two be separated fairly easily.
Has anybody tried this?
I'm fully aware of the dangers of fluorine chemistry and the toxicity of water soluble fluorides but this seems, with good precautions (certainly
gloves, goggles, dust mask and Ca gluconate cream at the ready), to be quite a safe method.
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not_important
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If the fluorite is finely powdered you might even be able to use boiling with aqueous Na2CO3, cryolite (Na3AlF6) when boiled with Na2CO3 or NaOH
solutions, and then more water added, leaves a sludge of Al(OH)3 and a solution of NaF.
The solubility of NaF in water doesn't change much with temperature, so if you concentrate a solution of NaF and Na2CO3 by booiling it down much of
the NaF will crystallise out. If you use NaOH, concentrate the solution somewhat and then add alcohol to precipitate the NaF.
With neutral fluorides such as NaF, there's no corrosive effects and calcium gluconate isn't needed, but gloves and a good dust mask are; it is a
skin irritant. The toxic dose of NaF is on the order of 5 grams. Skin contact should be handle by wiping it off, then washing with plenty of water.
A wipe-down with a solution of MgSO4 is good for clean-up, as that converts any NaF to the very low solubility MgF2.
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blogfast25
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Quote: Originally posted by not_important  | If the fluorite is finely powdered you might even be able to use boiling with aqueous Na2CO3, cryolite (Na3AlF6) when boiled with Na2CO3 or NaOH
solutions, and then more water added, leaves a sludge of Al(OH)3 and a solution of NaF.
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I'd expect cryolite to be more reactive than fluorite in these conditions because AlF3 does have (very limited) solubility in water, apparently. And
fluorite I have loads of, cryolite none whatsoever.
It's be worth trying ultra-fine CaF2, ground under water (to avoid losses of fine dust), either with concentrated soda or 50 % NaOH.
Thanks for the safety tips: I'd have expected the toxicity of NaF to be higher.
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JohnWW
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| Quote: Originally posted by not_important | (cut)
With neutral fluorides such as NaF, there's no corrosive effects and calcium gluconate isn't needed, but gloves and a good dust mask are; it is a
skin irritant. The toxic dose of NaF is on the order of 5 grams. Skin contact should be handle by wiping it off, then washing with plenty of water.
A wipe-down with a solution of MgSO4 is good for clean-up, as that converts any NaF to the very low solubility MgF2. |
Are you sure the lethal dose of NaF is as high as 5 grams? I thought it was much less than that. It works as a poison mainly by
precipitating Ca++ in the bloodstream and elsewhere as insoluble CaF2, and probably also interferes with chloride metabolism. In fact, the stuff was
once used, mixed with flour and finely grated cheese, as a rat poison.
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blogfast25
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A bit more searching for Fluorite+fusion, I found this interesting tidbit: an old method for the detection of the Fluorite in mixed minerals (or
fluorides in general):
http://www.minsocam.org/ammin/AM36/AM36_780.pdf
In acid conditions:
Zr4+ / Alizarine complex (purple) + 3 CaF2 ---> ZrF6 (2-) + 3 Ca(2+) + Alizarine (yellow)
A few other references to the Alizarine Zr4+ complex show that the formation of ZrF6 (2-) also happens when zirconyl chloride (ZrOCl2) is used as Zr4+
source.
In dept theory and practice of the test here:
http://etd.lib.ttu.edu/theses/available/etd-06302009-3129501...
This would seem to open up the possibility of fluorinating Zr by means of the most banal fluoride in the world, CaF2.
For instance by boiling acidified ZrOCl2 with an excess of fine CaF2:
ZrOCl2 + 3 CaF2 + 2 HCl ---> Ca(2+) + ZrF6(2-) + 2 CaCl2 + H2O
Assuming CaZrF6 is water soluble (?), filter and neutralise with ammonia to pH just below 7, then saturate with CO2 to precipitate CaCO3.
Filter and add a small excess of NH4F, now you have in theory a solution of (NH4)2ZrF6, NH4F and NH4Cl. Crystallize and dry, then drive off NH4Cl and
NH4F by heating.
(NH4)2ZrF6 decomposes to anhydrous ZrF4 and NH4F (see Brauer).
Similar route with NH4F instead of CaF2:
ZrOCl2 + 6 NH4F +2 HCl ---> (NH4)2ZrCl6 + 4 NH4Cl + H2O
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12AX7
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Seems plausible, for instance changing CaF2 to CaO should occur readily. But it will have to be hot. CaF2 melts around white heat. I doubt molten
Na2CO3 will react very quickly with CaF2. You'll have to get both hot enough that CO2 is bubbling out.
After fusion, the CaO / NaF mixture can be lixivated with acid; if NaF is low solubility, then neutralizing the CaO to soluble CaCl2 would be a good
way to loosen the mixture and filter out the NaF. Otherwise, dissolve the whole damn thing in an awful lot of water (then filter out the insoluble
crap that inevitably finds its way in), then precipitate Ca with CO2. And evaporate an awful lot of water.
Tim
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chloric1
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blogfast- I know of at least one ceramic supplier here has NaF for $3 per pound. It would surprise me if there was not such a supplier in England.
Consult Braur and you will note NH4F can easily made buy heating sodium flouride with ammonium chloride in a closed system. Ammonium fluoride loses
ammonia easily leaving the bifluoride which is quite soluble in water and would suffice for many HF applications. Or the ammonium fluoride would be
the root to a cornicopia of fluorides. Soluble fluorides like potassium fluoride and silver fluoride can be had with significant purity.
I would like my own ammonium bifluoride so I can make ammonium fluosilicate by bubbling silicon tetrafluoride into the bifluoride solution. The SiF4
made by heating cryolite or fluorspar with sulfuric acid and sand.
[Edited on 8/23/2009 by chloric1]
Fellow molecular manipulator
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Everado E. Dinavo
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5 grams of NaF is fatal? I had no idea fluoride was even that toxic at all, considering all the things they put it in...
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not_important
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| Quote: | | [quote...Are you sure the lethal dose of NaF is as high as 5 grams? ... |
MSDS http://www.jtbaker.com/msds/englishhtml/s3722.htm
says 5 to 10 grams, gives LD50 in sheep and goats as 100 mg/kg which is a similar dose to that 5-10 grams.
This MSDS http://msds.chem.ox.ac.uk/SO/sodium_fluoride.html gives similar LD50 values, but states that as little as 4 grams can be lethal.
BTW, NaF attacks glass to some extent, be aware.
| Quote: | | After fusion, the CaO / NaF mixture can be lixivated with acid; if NaF is low solubility, then neutralizing the CaO to soluble CaCl2 would be a good
way to loosen the mixture and filter out the NaF. Otherwise, dissolve the whole damn thing in an awful lot of water |
Um...that 'otherwise' step would attempt to create a solution of Ca(OH)2 and NaF, which would strive to become a solution of NaOH and precipitate of
CaF2. In fact that's the problem with any attempt to dissolve the calcium away from the NaF, CaF2 is far less soluble than NaF and so will be the
solids phase.
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blogfast25
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| Quote: Originally posted by 12AX7 | Seems plausible, for instance changing CaF2 to CaO should occur readily. But it will have to be hot. CaF2 melts around white heat. I doubt molten
Na2CO3 will react very quickly with CaF2. You'll have to get both hot enough that CO2 is bubbling out.
Tim |
I was thinking of about a 1,000 C, so above the MP of soda but below the MP of Fluorite. So liquid soda would be acting on finely ground CaF2. At that
temperature reaction should be quite swift I think. No need to decompose the formed CaCO3, quite the opposite. The mixture of unreacted CaF2,
unreacted soda, CaCO3 and NaF should be fairly easy to separate on solubilities alone. Very a la alchemists (LOL)
| Quote: Originally posted by chloric1 | | blogfast- I know of at least one ceramic supplier here has NaF for $3 per pound. It would surprise me if there was not such a supplier in England.
Consult Braur and you will note NH4F can easily made buy heating sodium flouride with ammonium chloride in a closed system. |
In the UK 'hazardous' chemicals can be very hard to get for non-institutional chemists. To be honest, I haven't really tried yet. NH4F would be
preferable because of the much higher solubility...
Polypropylene 'glassware' is to be preferred with soluble fluorides, if you don't want to ruin your Pyrex collection, it can withstand up to about 150
C (say steam bath). Any other material ideas?
| Quote: Originally posted by chloric1 |
I would like my own ammonium bifluoride so I can make ammonium fluosilicate by bubbling silicon tetrafluoride into the bifluoride solution. The SiF4
made by heating cryolite or fluorspar with sulfuric acid and sand.
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Brauer (p. 183, NH4F) claims solutions of NH4F cannot be evaporated without NH3 splitting off:
2 NH4F ---> NH4HF2 + NH3
Not a viable route to ammonium bifluoride?
[Edited on 23-8-2009 by blogfast25]
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chloric1
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Brauer (p. 183, NH4F) claims solutions of NH4F cannot be evaporated without NH3 splitting off:
2 NH4F ---> NH4HF2 + NH3
Not a viable route to ammonium bifluoride?
Yeh that exactly what I was referring to. The bifluoride of ammonia should easily be obtained with little fuss.
Fellow molecular manipulator
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blogfast25
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It would appear (from one source) that CaZrF6 is insoluble in water, perhaps unsurprisingly.
Does anybody have any date on the solubility of (NH4)2ZrF6?
The MSDS below:
http://www.gfschemicals.com/msdssearch/atn/MSDS%20US_English...
... claims its homologue (NH4)2TiF6 is insoluble in water.
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not_important
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Well, this is in HF/water solution, but it is a start
Also do a Web search for Zirconium and its compounds by Francis Preston Venable, copyright expired and downloadable as a 3 MB PDF.
[Edited on 25-8-2009 by not_important]
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blogfast25
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@not_important:
About 0.1 M in 10 N HF: that's definitely not very soluble.
The book's here:
http://ia340932.us.archive.org/1/items/zirconiumitscomp00ven...
Thanks for that! Now I have copy too, a real wealth of info on the multitude of fluorozirconates (an much besides that, of course). Haven't found any
solubility data on the ammonium salt yet but it does confirm the calcium (and barium) salt is insoluble in water.
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