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Author: Subject: Aqueous HF production...safety and risks
kazaa81
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shocked.gif posted on 8-9-2005 at 14:06
Aqueous HF production...safety and risks


Hallo to all,

just got some CaF2 mineral and get idea of convert it to HF with H2SO4 hot...
HF boils at 19°C so, while boiling H2SO4 it would go away as gas, which isn't the easiest thing to caught....can be the reaction done without heating, maybe below HF boiling point in a lead container?
For safety i will buy some Ca gluconate....

CaF2 + H2SO4 -------> 2HF + CaSO4

Some hint from someone who has prepared aqueous HF will be appreciated, because when searching on google about HF i only got "buy here! buy here!" etc...
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[*] posted on 8-9-2005 at 14:22


What container are you going to use?
HF dissolves glass and porcelain.

And I REALLY advise against this experiment, hydrofluoric acid is by far the most dangerous chemical one can have in the lab.

I have a 200ml bottle of the 40% aqueous stuff and I am too scared to even go near it. I need to get some Ca gluconate and make a gel from this, so that I have a chance of survival in case of a spill (however, the exposed bodypart will still need to be amputated).
I already have the required gloves (butyl rubber) but without the gel, I'm not going to open the bottle.
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Chris The Great
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[*] posted on 8-9-2005 at 14:54


I would think fluorine gas and nerve agents to be more dangerous, but either way HF is very very dangerous stuff.

I'd wear arm length rubber gloves, rubber apron, gas mask rated for HF, rubber boots, rubber everything! And have lots of Ca gluconate paste (or MgO paste, apparently that also works if applied quickly) in immediate reach, such as on your belt. Then, be very, very careful.

I think it's doable but you'll need to safe and protected to an extreme degree. And make sure your containers will handle the HF, nasty surprises are a big no-no with anhydrous HF.

You could distill it but it would need a very cold liquid in the condenser, and the reciever would have to be in a salt-ice bath.

Also, be sure to take your nieghbours into consideration when making anhydrous HF. While you may be covered in rubber with a gas mask, they aren't covered in rubber and have no gas mask, nor any gluconate paste sitting around.
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praseodym
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[*] posted on 9-9-2005 at 02:36


Got this from MSDS, think it should be useful:
Rubber gloves, face mask or safety glasses, apron, good ventilation. Do not work without calcium gluconate gel available to treat burns. Do not assume that gloves provide an impenetrable barrier to the acid. DO NOT WORK ALONE! Ensure that those working in the same laboratory are aware of how to treat hydrofluoric acid burns in an emergency.
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kazaa81
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thumbup.gif posted on 9-9-2005 at 11:55


I think which HF danger is a little exaggerated.....i was thinking to work with a lead container, because HF won't react with it. Yes, HF is dangerous, but also nitromethanes or lead acetate don't joke!
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[*] posted on 9-9-2005 at 16:10


Actually it's pretty bad, the fluoride ion is so small it finds its way into biological systems with suprising speed. Not to mention, most gloves do not provide adequate protection especially if a drop goes unnoticed for too long a time. The fumes I see as the most dangerous part as it has the capability to go directly into the lungs and cause tremendous damage there. No high schools and few colleges that I know of even permit the concentrated acid for student use because of the toxicity. A weak acid it may be, but it is dangerous to use in the home setting, especially without a fume hood.
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[*] posted on 8-10-2005 at 05:31
HF from CaF2 and H2SO4


The reaction is safe if you do the experiment outside.

Use a pressure cooker, sold to the escape a tube of copper, 3 to 4 feet .
Put in the cooker CaF2 and Sulfuric acid 95%. Close the cooker. Put the end of the coppe tube in a receiving flask containing pure water . I advice to use cold water, or ice . The reaction does not start right away. ... Afte a while, heat a little.

CaF2 + 2 H2SO4 -----> 2 HF + Ca(HSO4)2

You get impure HF because it is contaminated with H2SiF6.

The process works very well, an friend used it to get some HF to clean minerals.
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kazaa81
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[*] posted on 9-10-2005 at 12:28


Have you ever tried what you've wrote?

"Friends" often don't say things straightly as they've been....

Thanks all for help!
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[*] posted on 9-10-2005 at 22:25
mmmm, HF


The stuff really is QUITE nasty, and I'd recommending up some reports on people exposed to HF as well as the requisite personal safety and emergency response protols. This is one of thse rxns where you (and others around you!) stand to lose a whole lot - from mere nectrotic tissue on up to loss of limb and life.

Choice of container - teflon works - is also essential.
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