jamit
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copper fluoride
Just recently I purchased a bottle of rust Remover which contains hydrofluoric acid. I add about 50ml of HF to a beaker and added CuCo3 until the
fuzzing stopped. I added an excess of CuCo3 to make sure that there wasn't any HF remaining.
Next I filtered the solution and the filtrate was a clear blue solution, which I put into a evaporating dish. That was a big mistake -- it completely
stained and partially ate through it and evaporating dish was made of pyrex glass.
After a few weeks later, copper fluoride solid formed in the evaporating dish, including some crystals mixed with other contaminants.
My question is twofold:
It seems that copper fluoride attacks glass and stains just about everything except plastic or is my solution just to acidic and still contain
hydrofluoric acid?
Second question: has anyone made any copper fluoride crystals? They looks awesome but mines mixed with other non-crystalline solid and dissolving it
in water just destroys the crystals.
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Endimion17
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| Quote: |
It seems that copper fluoride attacks glass and stains just about everything except plastic or is my solution just to acidic and still contain
hydrofluoric acid? |
H+ does not eat trough the glass. F- does. And that's why water-soluble fluoride compounds are corrosive to glass. If it was because of the H+, then
HClO4 would've eat a whole lot of thin glass electrodes when doing a calibration.
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not_important
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Most fluoride salts hydrolyse in water, in effect forming "HF", even aqueous NaF will slowly attack glass. Use polyolefin containers when working
with aqueous fluorides.
see http://www.sciencemadness.org/talk/viewthread.php?tid=2424
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blogfast25
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Quote: Originally posted by jamit  | | Second question: has anyone made any copper fluoride crystals? They looks awesome but mines mixed with other non-crystalline solid and dissolving it
in water just destroys the crystals. |
Most here aren't daft enough to mess with HF solutions. What's the strength (HF %) of your 'rust remover'?
For CuF2 your best bet is probably reacting CuCO3 with a NH4HF2 solution in the right ratios, in a HDPE or PP container. CuF2 is listed as hygroscopic
so it's probably highly soluble in water. Evaporate perhaps in a copper container? MIND ANY HF FUMES!!!
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Mixell
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I know that HF attack glass via the following reaction:
SiO2 + 4HF --> SiF4 + 2H2O or SiO2 + 6HF --> H2SiF6 + 2H2O.
Do copper reacts in the same way?
SiO2 + 2CuF2 --> SiF4 + 2CuO or SiO2 + 3CuF2 --> CuSiF6 + 2CuO ?
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MrHomeScientist
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I noticed something similar when working with NH4HF2 recently. I bought it off eBay, and wanted to test to make sure it was what I ordered. I placed a
very small amount of the salt on the bottom of an overturned drinking glass (appropriated for lab use) and added a few drops of water. I left it for a
few hours, and nothing much happened. Upon acidifying with a drop or two of sulfuric acid, it finally started to visibly react (still slowly) and
frost the glass up. This frost was actually a layer of a gel-like material that scraped off. When doing this, I caught a whiff of a tiny amount of
fumes that was instantly sickening, a lot like the instant "bite" of chlorine fumes but still distinctly different. I'm fine now, but it was a very
scary experience since fluoride can take days to fully show symptoms. Now I can say I've been bit by all the halogens! (except astatine) I wouldn't
recommend it.
So in summary, yes soluble fluorides will etch glass by hydrolyzing in water even if you've gotten rid of all the original HF - as not_important said
above.
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Endimion17
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HF fumes are sickening, that's true. But only because we know how dangerous they are. It's more of a physchological effect than they're really
disgusting.
The smell of hydrogen fluoride is similar to hydrogen chloride, only more... "pure". It's difficult to describe. I'd say it's 90% burning and 10% that
something "different". HCl is more like 60:40, at least to my nose.
It's the smell of "damn it, it's burning my nose!", and once you combine the knowledge of the danger, you get that distinctive feeling of HF that is
so scary.
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blogfast25
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| Quote: Originally posted by Mixell | I know that HF attack glass via the following reaction:
SiO2 + 4HF --> SiF4 + 2H2O or SiO2 + 6HF --> H2SiF6 + 2H2O.
Do copper reacts in the same way?
SiO2 + 2CuF2 --> SiF4 + 2CuO or SiO2 + 3CuF2 --> CuSiF6 + 2CuO ?
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I vill exzplain ziz only onze, so pay attention.
ALL soluble fluorides hydrolyse to some extent because in Bronstedt acid-base terms, HF is actually a weak acid.
As a result, stable, soluble fluorides react like this:
Dissolution:
MF(s) === > M+ (aq) + F- (aq)
Hydrolysis:
F- (aq) + H2O (l) < === > HF (aq) + OH- (aq)
This equilibrium leans to the left but means that all stable fluoride solutions:
1. Contain small amounts of free HF, which then reacts with glass as described.
2. Are slightly alkaline.
It’s no different from acetate solutions smelling slightly of vinegar (acetic acid).
| Quote: Originally posted by Endimion17 | HF fumes are sickening, that's true. But only because we know how dangerous they are. It's more of a physchological effect than they're really
disgusting.
The smell of hydrogen fluoride is similar to hydrogen chloride, only more... "pure". It's difficult to describe. I'd say it's 90% burning and 10% that
something "different". HCl is more like 60:40, at least to my nose.
It's the smell of "damn it, it's burning my nose!", and once you combine the knowledge of the danger, you get that distinctive feeling of HF that is
so scary. |
NEVER, EVER downplay the dangers of HF: anhydrous, water solutions, gas or water soluble fluorides.
[Edited on 16-8-2011 by blogfast25]
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Endimion17
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I'm not following you. Where did I downplay its danger? I simply described its smell as "burning", and in fact it barely has a smell.
What's with the paranoia? Nothing will happen to your nose if you just feel the smell of very dilluted aerosol of HF. It's not VX or DMM, and it's not
like anyone's going to sniff it and inhale it like a bag of green apples.
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blogfast25
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Endimion17:
Paranoia??? If I detected the smell of HF w/o knowing it's precise source (and thus quantity) I'd evacuate like a shot. HF is far more dangerous than
HCl. HF gas is quite soluble in body tissue, among other reasons because it doesn't dissociate as much as HCl. Once in the body it causes Ca2+ to
precipitate as CaF2 with disastrous results. HF in it's various forms is one of the most dangerous laboratory chemicals.
"HF fumes are sickening, that's true. But only because we know how dangerous they are. It's more of a physchological effect than they're really
disgusting."
Many would consider that downplaying.
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Endimion17
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| Quote: Originally posted by blogfast25 | Endimion17:
Paranoia??? If I detected the smell of HF w/o knowing it's precise source (and thus quantity) I'd evacuate like a shot. HF is far more dangerous than
HCl. HF gas is quite soluble in body tissue, among other reasons because it doesn't dissociate as much as HCl. Once in the body it causes Ca2+ to
precipitate as CaF2 with disastrous results. HF in it's various forms is one of the most dangerous laboratory chemicals.
"HF fumes are sickening, that's true. But only because we know how dangerous they are. It's more of a physchological effect than they're really
disgusting."
Many would consider that downplaying. |
Yes. Paranoia. HF is very toxic (one of few chemicals I'm actually quite afraid of), but taking few whiffs of aerosol so dilluted that it's far below
the allowed occupational concentration is not dangerous.
A chemist has to know what HF smells like, and he can learn that in a safe way by taking a few light whiffs from a bottle, and not breathe full lungs.
I never smell something in the lab in a way I smell roses.
Another thing is if you enter a room that is full of aerosol. Every normal person knowing what happened will try to get out quick, and avoid
breathing.
A chemist must know how phosphorus smells like, too. Yes, WP causes phossy jaw, but not if you smell it few times in your life.
There are something called doses and exposure.
You're expressing pure paranoia. Relax, man.
And regarding to the downplaying, that few lines of text I wrote are an explanation why HF seems to have a scary smell. It doesn't. It smells almost
of pure "noseburn", and if our brains know that it's very toxic, we experience the smell a lot different, adding the flavor to the smell.
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blogfast25
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Nope. No paranoia. Just common sense. Go tell someone else to relax. LOL.
Love your psychological spiel too: se non e vero, e ben trovato!
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Bezaleel
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Could some one please inform me how dangerous hydrogen fluoride is in comparison to hydrogen cyanide or hydrogen sulfide?
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blogfast25
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These comparisons aren't really easy to make. Toxicity depends on quite few factors. As a rough guideline you can use the LD 50 which can be found
easily on the net for these substances. But how the material entered the body, at what rate, in what physical form and other factors make a
back-to-back comparison almost impossible.
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