Straight Dope Message Board

[Wesley Clark]

Are they made out of materials that are already hydrogen saturated and cannot accept another hydrogen like saturated single bond carbon chains (a carbon bonded to two carbons and two hydrogens)? Or are they made of something totally different? The only way I can think of making an acid proof container is making the interior out of a material that cannot accept hydrogens, and carbon with 2 hydrogen bonds and 2 carbon bonds is the only material I can think of that would fit this bill and still be affordable and malleable enough to work.

[_xiao_wenti_]

Well it really depends on the acid. Generally glass (with outer plastic sheathing) is sufficient for most acids. For acids like Hydroflouric, glass is dissolved, so plastic PTFE is used.

[HMS Irruncible]

As mentioned above, every acid I've ever seen has been stored in glass, pyrex, or plastic containers. Hydrofluoric acid is of course much stronger, so it has to be stored in a special king of material (don't remember what we kept it in but it was close to teflon).

Incidentally, if you're playing around with acid, don't mess with hydrofluoric. Not only is it corrosive, but it is acidic, and even small burns can kill you within hours, days, or weeks. .

[Speaker for the Dead]

Originally Posted by NattoGuy

Incidentally, if you're playing around with acid, don't mess with hydrofluoric. Not only is it corrosive, but it is acidic, and even small burns can kill you within hours, days, or weeks. .

Some acids aren't acidic?

[HMS Irruncible]

Originally Posted by Speaker for the Dead

Some acids aren't acidic?

I didn't mean to say acidic, I meant to say TOXIC!!!!!


I'm going to make myself some coffee now and maybe take a day or two off from posting. Obviously I've tripped a breaker in my head somewhere.

[spingears]

Originally Posted by Wesley Clark

....
the only material I can think of that would fit this bill and still be affordable and malleable enough to work.

Concentrated Sulphuric Acid is stored and shipped in steel tanks.

[Gfab912]

Originally Posted by NattoGuy

As mentioned above, every acid I've ever seen has been stored in glass, pyrex, or plastic containers. Hydrofluoric acid is of course much stronger, so it has to be stored in a special king of material (don't remember what we kept it in but it was close to teflon).

Incidentally, if you're playing around with acid, don't mess with hydrofluoric. Not only is it corrosive, but it is acidic, and even small burns can kill you within hours, days, or weeks. .

Hydrofluoric acid

I did a google search on this acid... nasty nasty nasty! I'd hate to have to work with it (industrial-type stuff). Just thinking about the pain that it would put me through BEFORE the doctor had a chance to cut off my hand would be enough for me to quit that job!

[mks57]

Hydrofluoric acid used to be stored in wax bottles.

[Excalibre]

Originally Posted by NattoGuy

As mentioned above, every acid I've ever seen has been stored in glass, pyrex, or plastic containers. Hydrofluoric acid is of course much stronger, so it has to be stored in a special king of material (don't remember what we kept it in but it was close to teflon).

Incidentally, if you're playing around with acid, don't mess with hydrofluoric. Not only is it corrosive, but it is acidic, and even small burns can kill you within hours, days, or weeks. .

It's not that hydrofluoric is particularly strong (it's a weak acid, actually) but the fluoride ions are particularly capable of attacking glass - I'm not sure why, but fluorine is highly electronegative and one of the most reactive elements there is, so I assume it has to do with that. If you splash it on yourself, the fact that it's weak is a further problem - there's no burning sensation right away, but the fluoride ions can actually attack the calcium in the bones, throwing electrolytes all out of whack and, you know, dissolving your skeleton.

Most other strong acids can be stored in glass. I can certainly attest that hydrochloric, sulfuric, and nitric acids (all strong acids) are stored in glass jars even in their most concentrated forms.

[Ruken]

Originally Posted by Excalibre

If you splash it on yourself, the fact that it's weak is a further problem - there's no burning sensation right away, but the fluoride ions can actually attack the calcium in the bones, throwing electrolytes all out of whack and, you know, dissolving your skeleton.

AFAIK, the major concern is not that your skeleton is turning into jelly, but that the sudden spike of Ca2+ in your blood stops your heart.

My lab had some sort of safety inspection before I joined it this semester. The results were given back a few weeks ago. One of the citations listed was that someone in my room was using HF w/o any calcium gluconate ointment nearby . I'm not sure who it is, but I hope he's not using it any more, and I really hope it's not the guy who works next to me, since he seems rather cavalier about safety issues.

[Lemur866]

Fluorine ions are the only ions more electronegative than oxygen ions, which is why only hydrofluoric acid is able to disolve Silicon Dioxide (i.e glass). Nothing else can form a lower energy compound than oxygen, so even the nastiest acids can stored in glass. Fluorine would be a better oxidizer than oxygen, except there isn't much of it around. Which is why we breathe oxygen, not fluorine.

Remember all those chlorine-breathing aliens from the 50s? Chlorine would also work fine from a chemistry perspective, despite being slightly less electronegative than oxygen. The trouble is that there is much less chlorine in the universe than oxygen. It would be very unusual to have a planet with enough clorine concentrated in the crust for it to be used that way in the biosphere.

[chrisk]

cotinuing on the hijack, I remember reading an article or other account (possibly written by Isaac Asimov in his prodigious non-fiction mode) about the exploration of fluoronic chemistry, particularly the attempt to actually refine and isolate the element fluorine itself, and how many good chemists died along the way from fluoride poisoning.

As you might imagine, with fluorine being possibly the single chemical element with the most powerful tendency to bond to other elements, it's very hard to isolate and purify it.

[chrisk]

Originally Posted by Lemur866

Fluorine would be a better oxidizer than oxygen, except there isn't much of it around. Which is why we breathe oxygen, not fluorine.

Remember all those chlorine-breathing aliens from the 50s? Chlorine would also work fine from a chemistry perspective, despite being slightly less electronegative than oxygen. The trouble is that there is much less chlorine in the universe than oxygen. It would be very unusual to have a planet with enough clorine concentrated in the crust for it to be used that way in the biosphere.

By the way, does anybody know WHY fluorine is less common, on a universal scale, than oxygen? Chlorine I understand is a heavier nucleus, about twice the weight of oxygen, and thus less likely to be fused in stars... and yet it's probably still light enough to be keeping a higher ratio of energy than, say, iron.

But fluorine is right next to oxygen, carbon, and nitrogen, which are all significantly more common I believe. Is the nucleus of fluorine less stable? I remember a little about the 'CNO' cycle in certain stars from university... does that mean that the nucleus of oxygen is more likely to break down (into carbon and helium, or carbon and an alpha ray to put it another way,) than to build up into the next nuclear type?

Did that question make any sense??

[umop ap!sdn]

Originally Posted by Ruken

AFAIK, the major concern is not that your skeleton is turning into jelly, but that the sudden spike of Ca2+ in your blood stops your heart.

I'm confused... CaF₂ is insoluble. Does enough of it manage to dissolve anyway, or does the presence of phosphates in the bone have something to do with it?

[OldGuy]

Originally Posted by chrisk

But fluorine is right next to oxygen, carbon, and nitrogen, which are all significantly more common I believe. Is the nucleus of fluorine less stable? I remember a little about the 'CNO' cycle in certain stars from university... does that mean that the nucleus of oxygen is more likely to break down (into carbon and helium, or carbon and an alpha ray to put it another way,) than to build up into the next nuclear type?

Did that question make any sense??

As I recall there are two reasons. First when the stars "burn" hydrogen they form Helium with 4 nuclear particles. Later when they "burn" the heliums by fusing, they naturally tend to form a nucleus with a multiple of four particles (like oxygen with 16). Secondly, nuclei with an even number of protons and an even number of neutrons are more stable (at a lower energy level) than those with odd numbers. Oxygen has 8 of each. Fluorine has an odd number protons (9) . (I believe it's most common isotope has 10 neutrons, but am not positive.

[chrisk]

Originally Posted by umop ap!sdn

I'm confused... CaF₂ is insoluble. Does enough of it manage to dissolve anyway, or does the presence of phosphates in the bone have something to do with it?

Ruken didn't say CaF₂... he said Ca₂₊ I believe... a single calcium ion, double positive charge.

Originally Posted by OldGuy

As I recall there are two reasons. First when the stars "burn" hydrogen they form Helium with 4 nuclear particles. Later when they "burn" the heliums by fusing, they naturally tend to form a nucleus with a multiple of four particles (like oxygen with 16). Secondly, nuclei with an even number of protons and an even number of neutrons are more stable (at a lower energy level) than those with odd numbers. Oxygen has 8 of each. Fluorine has an odd number protons (9) . (I believe it's most common isotope has 10 neutrons, but am not positive.

Not sure if that explains the relative abundance of nitrogen versus fluorine... assuming that there is a disparity there.

[umop ap!sdn]

Originally Posted by chrisk

Ruken didn't say CaF₂... he said Ca₂₊ I believe... a single calcium ion, double positive charge.

CaF₂ = Ca²⁺ + 2 F^-. Reactions that dissolve or corrode a substance do so by converting it into soluble compounds, hence my confusion given that calcium fluoride is insoluble.

Anyway it just occurred to me that if there are chloride ions in the blood, the hydrofluoric acid would effectively free them up for dissolving the calcium.

[OldGuy]

Originally Posted by chrisk

Not sure if that explains the relative abundance of nitrogen versus fluorine... assuming that there is a disparity there.

Nitrogen is much more abundant in the universe than Fluorine. The Universe is 87% hydrogen, 12% He. Oxygen, Carbon, and Neon are the next three . Nitrogen jumps ahead of neon if you measure abundance in just the solar system and is about 3000 times as abundant as Fluorine. I'm not sure why.

[chrisk]

Originally Posted by umop ap!sdn

CaF₂ = Ca²⁺ + 2 F^-. Reactions that dissolve or corrode a substance do so by converting it into soluble compounds, hence my confusion given that calcium fluoride is insoluble.

Whoops, my mistake kinda - I hadn't been following the whole discussion and somehow thought that the fluorine was displacing the calcium from the bones, (though that obviously doesn't make sense if you consider the charges.) Your analysis would seem to be correct.

What makes calcium fluoride insoluble?? I would think that both of the ions would be soluble seperately, though possibly a solid piece of calcium fluoride is bound together so tightly that it resists water's efforts to dissolve it. If so, then calcium fluoride forming in water solution might tend to precipitate out... which could be part of the problem, in bloodstream.

Nitrogen is much more abundant in the universe than Fluorine. The Universe is 87% hydrogen, 12% He. Oxygen, Carbon, and Neon are the next three . Nitrogen jumps ahead of neon if you measure abundance in just the solar system and is about 3000 times as abundant as Fluorine. I'm not sure why.

May have something to do with nucleus stability then, and/or the tendency for oxygen to alpha decay under certain circumstances rather than stick around for more proton bombardment.

[Ruken]

Originally Posted by umop ap!sdn

I'm confused... CaF₂ is insoluble. Does enough of it manage to dissolve anyway, or does the presence of phosphates in the bone have something to do with it?

Your confusion results from me being wrong. CaF₂ is indeed insoluble. You become hypocalcemic, meaning your [Ca²⁺] drops. This screws with your heart. I don't pretend to understand enough about bio to understand how this works.

[HMS Irruncible]

Originally Posted by Ruken

Your confusion results from me being wrong. CaF₂ is indeed insoluble. You become hypocalcemic, meaning your [Ca²⁺] drops. This screws with your heart. I don't pretend to understand enough about bio to understand how this works.

The insolubility is exactly the problem. The calcium gets bound up in salts, instead of being where it should be - dissolved in your blood and keeping your muscles working, especially the heart.

And HF does burn, perhaps not as much as other acids, but it does cause pain and skin lesions in sufficient concentrations.