As this is my first post, I should start by saying hi to everyone. I've been a lurker, just floating around reading posts for a long time and finally
decided to set/register an account. Anyway, I love the forum, you guys have been a invaluable source of information both regarding my hobby and
course.
Basically I've been making my own hydrochloric acid for quite some time, by reacting 'Rhino' 98% sulphuric acid toilet and drain cleaner with NaCl.
Can't really get much more simple a procedure and i've got it down to an art. However, I've been interested in investigating the properties of
hydrofluoric acid for some time! Now I know hydrogen fluoride gas is hideously toxic and that the acid itself isn't much better so I want to just run
this idea through the forum, as I'm sure someone here will be capable (much more so than I am) of pointing out any flaws. Any advice is welcome, just
to point out that i'm not talking about making 5 litre of concentrated acid, maybe just 100ml or so of fairly dilute stuff! I think I'm aware the the
risks involve, however if anyone feels that in-fact I'm not, then please tell me!
Right, my method is simple. A single displacement of the fluorine from a halide salt, SO4 (from conc sulphuric acid).
I.e.
CaF2 + H2SO4 ==> CaSO4 + 2HF
this works for most metal halide salts and I know it works well for KF, but can I use the same setup for HF as for HCl gas? also what are the best
safety precautions I can take?
Finally my setup consists of a simple gas generator; that is, a Buchner flask, with a 100cc syringe attached to the side arm (allows controlled
addition of the sulphuric acid). The mouth of the flask is stoppered with a rubber 1 holed bung, to which an glass delivery tube is attached. This
runs to the bottom of a 250ml measuring cylinder which is again stoppered at the top, this time with a 2 holed bung. Finally another (rubber) tube
takes excess gas and bubbles it through a 90% NaOH solution.
Additionally I'd like to know if NaOH will work as an absorbent for excess gas with HF, and also if CaF2 would work as a source. It would be the
easiest substance to get a hold of, as fluorite crystals! Unless someone knows a source of sodium fluoride etc.
Thanks,
NiK Bot0nist - 22-5-2013 at 07:17
Rubber will be a problem. Be very carefull. even some of our most matuer and experianced home chemists would never dream of producing HF gas. I,
personally, would rather generate HCN myself. HF is a demon...
Also, have you done some forum searches? What threads and advices have you found?Endimion17 - 22-5-2013 at 07:43
Before attempting to do any experiments with HF, familiarizing yourself with its properties would be a great idea. For example the fact it corrodes
glass, so any attempts to make it in a glass container will fail.
Also, remember that if you spill it on your hand, you're on the path to get your hand amputated unless you work quickly.
100 ml? LOL, seriously? Don't even try that, even if it's dilute. I'd be happy to try that with 5 ml...Bot0nist - 22-5-2013 at 08:00
Please don't try to make HF yourself. You almost certainly will maim yourself for the rest of your life.
Instead try to make HBr, which is quite a challenge also, due to the ease of oxidation of this compound while it is prepared. HBr is more interesting
as well and can be handled at home, just like HCl. There are many other compounds, which may be interesting for you to make. Making HNO3 is another
option, also quite interesting to make and interesting to have. Can be risky also, but not even remotely as dangerous as making HF.Dr.Bob - 22-5-2013 at 11:39
Those photos scare me and I have worked with HF. We did at least have the necessary burn kits and other safety equipment, plus Teflon type labware
and special HF manifolds. As stated in another thread recently, HF is not very safe or easy to work with, even with the proper equipment, and very
bad without it. Even with some experience in the area, I stay away from it unless it is absolutely needed. Also, this work should not be done in
residential spaces unless you live alone away from any one else. NiCoLi_BrLiNTe - 22-5-2013 at 12:53
I have indeed done some forum searches and was initially surprised by a near total lack of information relating to the use or production of HF.
Although perhaps it's not that surprising, given what its capable of! I knew it was strong, but after reading your posts and then looking online i'm
starting to think maybe about leaving it alone. I read that the burns don't hurt until 20-30 minutes after contact, and by the time they do you're
already screwed. Also that once its got through your skin it can be transported around your body causing permanent damage to your circulatory system
(which carries it), organ damage, CNS/PNS damage, skeletal/skeletal muscle damage and finally death.
I guess I shouldn't need to ask this but, what about buying hydrofluoric acid, they sell it in smallish quantities (250ml) at 48% for glass etching
and other niche uses. That would at least take care of the risks of gas leaks and liquid transfer?
Oh, and thanks woelen! I've made HNO3 before, but I've never seen HBr so would be very interested in making it; I know I'm being lazy now, but what
are some examples of things I could do with HBr that one can't do with HCl?
