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IrC
International Hazard
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I don't want to sound rude but playing with HF with your obvious lack of knowledge and experience on the subject sounds dumber than a box of rocks if
you ask me. You are talking about one chemical so dangerous virtually every university on the planet has removed it from storage, and only stock it
for specific projects and even then only allow certain specially trained people to deal with it. Near the window? Which way is the wind blowing? I
just hate to see the loss of an up and coming new mad scientist, so I will say goodbye to you now while the chance still exists.
You might do a study of the effects on your heart of hypocalcemia, that is when all the calcium in your bloodstream is bound up and nerve impulses
telling your heart to beat are no longer there. Not to mention amputation of limbs when your bones have been converted to calcium fluoride.
http://www.inchem.org/documents/pims/chemical/hydfluor.htm
I strongly urge you to print this out and glue it to your forehead, only to be removed when you have memorized every word therein.
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oneup
Harmless
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Well, woelen is still alive....  
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IrC
International Hazard
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"Well, woelen is still alive."
If so I imagine he has a very good understanding of what he is doing and treats HF with the utmost care and respect. Somehow I doubt he would ever
work with this stuff near a window trusting to luck that the air was flowing out instead of in. Likely he works on it with nitrile gloves, proper
gear, fume hood containment with positive airflow out of the building, and carefully plans each move he makes.
Either that or he is really lucky so far.
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Magpie
lab constructor
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By their very nature kewls are an endangered species. As IrC has pointed out they are broodstock for mad scientists. As such we cannot afford to
needlessly let them kill themselves.
I think that the members of this board have done a really good job of warning oneup about what a lethal substance he is contemplating toying around
with.
The single most important condition for a successful synthesis is good mixing - Nicodem
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oneup
Harmless
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| Quote: | Originally posted by Magpie
I think that the members of this board have done a really good job of warning oneup about what a lethal substance he is contemplating toying around
with. |
Well, they did don't really think i'm gonna do this anymore... HF is probably
even more dangerous then nitroglycerin, altough i've made it over and over again and still have all 10 fingers.
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chromium
Hazard to Others
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Thanks to IrC for Pim link. Very usefull. It seems that HF fumes are not so deadly as spilling it to the skin. Almost sole reason of its incredible
toxicity is ability to precipitate all calcium in your blood, and skin is not barrier for HF.
Calcium gluconate is not only substance that can be used to neutralise HF on your skin. Magnesium sulfate solution is mentioned several times and all
soluble calcium salts probably work. Maybe even calcium acetate that can be made by neutralisation of vinegar with lime. Soda that you use in case of
other acids is not effective here as problem is not acidity of HF but its ability to precipitate calcium.
There is one more safety concern that no one mentioned so far. If there is reaction with some gaseous products then some amounts of liquid will be
sprayed onto nearby things. Its not enough if you just do not drop anything onto yourself. Outer surface of test tube, stative clamp and even tabletop
may also get contaminated. Do not expect that all small drops will be seen. So you need to clean everything very carefully before you (or anyone else)
can touch anything without gloves.
[Edited on 4-1-2006 by chromium]
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garage chemist
chemical wizard
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Hydrofluoric acid is very useful, it gives many reactions that the other hydrogen halide acids don't give.
For example the formation of fluoroboric acid: dissolve a stochiometric amount of boric acid in 40% hydrofluoric acid (caution: exothermic!), and
after 24 hours you can fill the solution of HBF4 into a glass bottle for storage. It contains absolutely no HF any more.
The solubilities of the alkali fluoroborates are nearly the same as those of the corresponding perchlorates: the potassium salt has very low
solubility.
I once performed the preparation of potassium fluoroborate (from Schlessinger Inorganic Laboratory preparations), using 40% HF. I got the HF from my
dad who uses it at work (though very seldom) and brought me some. He knows that I am able to handle it safely.
I used a face shield (motorbike helmet) and gloves made of butyl rubber during the preparation, and worked under the fume hood.
However, 40% HF does not fume visibly at room temperature.
Only the 70% acid strongly outgasses HF.
I dissolved the H3BO3 in the HF (measured quantities), it got quite warm and I had to stop during the addition in order to wait for the solution to
cool down, as it began fuming.
After complete addition of the H3BO3 I let it stand over night and the next day added K2CO3 solution.
The KBF4 precpitated, although it was not visible snce the refractive indices of water and KBF4 are nearly the same.
After filtration it was apparent that the yield was excellent (over 95%, since the solution was very cold).
By heating potassium fluoroborate with boric oxide (B2O3), boron trifluoride gas is produced in good yield (see Brauer for a procedure) which can be
dissolved in diethyl ether to form the etherate. I haven't tried this yet, the KBF4 still sits on my shelf.
[Edited on 4-1-2006 by garage chemist]
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IrC
International Hazard
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http://www.inchem.org/pages/pims.html
To see others check out this link. I find them so much better than MSDS. I just wish this pim page listed more chemicals than it does. I remember
reading somewhere that hydrofluoric acid starts fuming at 48 percent.
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woelen
Super Administrator
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| Quote: | Originally posted by IrC
"Well, woelen is still alive."
If so I imagine he has a very good understanding of what he is doing and treats HF with the utmost care and respect. Somehow I doubt he would ever
work with this stuff near a window trusting to luck that the air was flowing out instead of in. Likely he works on it with nitrile gloves, proper
gear, fume hood containment with positive airflow out of the building, and carefully plans each move he makes.
Either that or he is really lucky so far. |
Yes, I'm still alive, or is this my avatar posting here?? .
To put things seriously. If you ever do an experiment with HF, only use mg quantities. In my experiment I only used 100 mg NaF, resulting in formation
of appr. 45 mg of HF. Most of this remains in the liquid and in the test tube, so the amount, escaping into the air is limited to a few mg.
Besides that, I used the following safety measurements:
The experiment was performed under a fume hood, which guarantees that air is blown outwards, so there cannot be buildup of fumes.
The test tube was not taken in my hand. Not even when I wear gloves, I take a test tube with HF in it in my hands. I used a clamp to hold the test
tube. This is something which I mostly do with dangerous stuff.
After the experiment was done, I immersed the test tube under water in a large tub at once, diluting and cooling down the acid immediately. The clamp
was rinsed at its end carefully.
But, the single most important thing is to use small quantities. Also on my site I mention several times not to scale up the experiment.
Something which I also are very precise at is preventing long-term low-level exposures. I'm very careful not to contaminate my work area with
chemicals. So, I take a lot of time and a lot of water for cleaning up, when I'm done with an experiment.
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oneup
Harmless
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You should actually go to some kind of remote place, put a big glass jar on the ground, put in a kilo of NaF in it, position a flask with a litre or
so sulfuric acid and some kind of system so you can mix the chems 500m away. now that would be impressive!
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IrC
International Hazard
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Oneup it sounds like you may have missed the point, and that is do it a little at a time with the proper planning and protection. Why make a bunch of
HF anyway? Only have around just the amount needed for an experiment and no more, doing small amounts in each experiment. Woolen even carefully cleans
up between each thing he does, and this is along with the other things he mentioned. Reading his writing here and on his website tells me he is one
hell of a good researcher who plans and does everything carefully and with complete knowledge. Before you start doing things in chemistry you must
first develop these skills and practises. Chemistry will do you no good without first learning safety.
I am not trying to be a boring lecturer here but your last post tells me that you still need to work on the kewlness factor.
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oneup
Harmless
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I wasn't serious
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DrP
National Hazard
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I needed a high temp resistant polymer for a test I was doing - I thought about using PTFE - this would be great, however I believe that HF is
generated when the stuff burns and that it has a habbit of dissolving furnace linings apparently (being SiO2)  .
This can't be very concentrated as I've heard the effects of being near to burning PTFE lead to something they call polymer flu (rather than death) -
like the flu but much much worse. I got some samples of a PTFE emulsion but decided not to go ahead with the experiments just in case.
Also - parrots and budgies kept in kitchins have died due to PTFE linings degrading from saucepans and frying pans giving small amounts of HF.
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12AX7
Post Harlot
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Although I'm sure HF is present in small amounts, Teflon decomposition is mostly a hodge-podge of perfluoroalkanes and -enes, with varying amounts of
oxygen and hydrogen depending on conditions I'm sure. Nothing healthy at any rate.
Tim
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Endo
Hazard to Others
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I use HF almost weekly to prepare samples when assaying them for TiO2 content. We dissolve/digest an ashed sample in a mixture of 45% HF and HCl warm
it to dryness and redissolve in HCl prior to analysis by AA.
It is a very useful acid, because it can dissolve the refractory metal oxides that normally are not touched by most acids. I have always used it in a
fume hood, with calcium gluconate at hand.
Containers usually are made of PEEK or Teflon, and our digestion happens in a platinum crucible.
I did get some on my hand once, (it had spattered from a crucible out of the fume hood, sash was up a few inches) I knew what it was and immediately
got it under the faucet, probably 2-3 seconds max, I washed it for around 20 min and then put on calcium gluconate. I escaped with a rough little
sore that took a couple weeks to heal.
I have a co worker who got a hole in his glove while mixing solutions to clean silica depostits from a boiler. He got a drop on the tip of a finger
and dealt with the excruciating pain for several days afterward... and yes the fingernail fell off.
I think there are commercially available paints that turn from a dark blue to yellow when HF is in contact with them, in fact the HF from Fisher sci
has all the labeling done with this paint so you can tell if someone has dribbled some down the side of the bottle. I wonder what reaction it uses, I
know it is reversable because the paint changes back to blue after you wash the bottle off.
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Ron
Harmless
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Oneup, you have been pointed in the direction of some fine information regarding the dangers of this chemical but just in case you havn't read the
important bits here's something you may have missed:
Hydroflouric acid doesn't just burn. IT DISOLVES YOUR BONES!!!
Also, you may end up needing to have the calcium gluconate injected subcutaneously. Bugger that(as they say).
I just realised this thread is a bit old but I'll leave this post here anyways. Any noobs who aren't familiar with the ever-charming bone dissolving
action of hf acid may benefit from seeing it in black and white.
[Edited on 29-3-2006 by Ron]
[Edited on 29-3-2006 by Ron]
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atabilgin
Harmless
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purifiy to H2SO4 from H2SO4- HF solution
help me please!!!
how can I purify to sulfuric acid from H2SO4 - HF solution?
Do you know a method at this subject?
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12AX7
Post Harlot
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Add some calcium hydroxide. Calcium fluoride is less soluble than calcium sulfate (mind that CaSO4 is still pretty insoluble, so don't overdo it).
Tim
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woelen
Super Administrator
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If you don't mind loosing the HF, then you could heat the liquid and keep it boiling for quite a while. The HF boils away, together with most water.
What remains is 96% H2SO4 (the azeotrope with water).
Keep in mind though that this operation is VERY dangerous. This MUST be done outside or in a good fumehood, because all HF is expelled from the liquid
as gas and this stuff is really toxic!
Also keep in mind, that you need a special vessel to perform this reaction in. Glass is attacked by the liquid, containing HF, especially when it is
hot. You need some vessel, which withstands HF and on the other hand it also should withstand very hot sulphuric acid. I'm not sure, which material
withstands both conditions, probably you need some teflon coated vessel.
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12AX7
Post Harlot
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Wouldn't lead do it? I mean, until you reach sulfuric acid's boiling point and it melts...(pretty close there if I recall correctly!)
Checked, H2SO4 actually boils just 10C above pure lead's melting point, LOL!
Tim
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neutrino
International Hazard
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Large amounts of HF gas are not to be played around with. One whiff and you're good as dead. Let's not forget about those downwind of us. I hope you
live out in the middle of nowhere.
Especially if you live in the US, you risk the effects of public paranoia. I'm sure we are all familiar with those.
A likely headline:
"Terrorist unleashes chemical attack on city"
I wish I were kidding...
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IrC
International Hazard
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Why couldn't you bubble the HF gas through a trap full of water half filled with CaCO3 chips, turning the HF into Calcium Fluoride as fast as it is
produced?
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chromium
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If this is Na2CO3 solution with CaCO3 chips then it will work even beter as dissolved Na2CO3 gets better contact with HF. This will also give CaF2 as
product because it has far lower solubility than NaF.
Anyway this is rather dangerous and i would not do this without lot of thinking and experimenting with setup before puting HF containing substances
into it.
[Edited on 3-4-2006 by chromium]
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IrC
International Hazard
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No doubt anything involving HF is dangerous, but the idea seemed better than just venting HF into the air outside. I like the addition you suggested
as it would make an even more efficient HF scrubber. Coming up with the materials for the plumbing and vessels would also be problematic insofar as
anything HF is concerned. Myself I just have no desire to play with HF, the 125 ml bottle of it I bought is double contained and I have never found a
use for it. I bought it when I was thinking about ways to get some actinides from ores and decided against the entire idea after much study. The more
I read about HF and it dangers, and the real materials problems in dealing with it, the less I liked the idea of doing any experiments with it.
At some point in time I started not wanting to own chemicals which had real problems when it came to disposing of them. I got rid of my ammonium
biflouride as it could be shipped to someone who could use it but the HF was merely mailed to me in a bottle in a box with some peanuts around it.
After looking into the postal regulations I realized what an idiot the guy who sold it to me was, and no way was I going to take such risks with some
poor innocent mail carrier. I read about the New York trash collector who died after breathing the fumes from a bottle of 49 percent Hf which some
high school kid had thrown away. He was the man who rode the truck on the back picking up the cans and as the load was squished the bottle burst and
the fumes killed him. Just imagine being responsible for killing an innocent soul. I still wonder if the kid knew he had killed someone when I think
about that story.
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atabilgin
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thanks! for evrytings...I will try carefully
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