Why Does Hydrogen Fluoride (HF) Pose a Danger?

[ShawnD]

It's not a strong acid, it's not an oxidizer, it's not a reducer. What does it do?

 

[christinono]

I did a bit of research and found info at this site:
http://www.mnpoison.org/index.asp?pageID=151

Apparently, it is very dangerous because of its ability to penetrate tissue (causing severe burns).

 

[movies]

It also reacts with the calcium in your bones to make CaF2, which is very insoluble in pretty much anything. That's not a good thing. The treatment for exposure is essentially a calcium supplement, I think.

 

[ShawnD]

Thanks for the info.
How does HF penetrate skin so quickly, and how does HF eat glass?

 

[movies]

The fluoride reacts with the silicon atoms in the glass. The Si-F bond is very strong (check out some bond energies here: http://www.cem.msu.edu/~reusch/OrgPage/bndenrgy.htm )

 

[Gokul43201]

We do a bunch of GaAs (gallium arsenide) processing in our lab. The etchant for GaAs has traditionally involved HF because that gives you a fast, anisotripc etch with GaAs, which is otherwise very hard to dissolve. Over the last decade or so, people have been switching to slower alternatives, from hearing scary stories about HF disasters. I, for one, was extremely relieved, when we were able to establish our processing procedure such that it entirely eliminated HF (and Br2, which is another common solvent in this field).

I think the reason that HF penetrates so deep is because the fluoride ions are stabilized only by calcium or magnesium ions, found mostly in bone tissue. Soluble salts also are formed with other cations but dissociate rapidly. Consequently, fluoride ions release, and further tissue destruction occurs. Another property that makes HF such a hazard is its high vapor pressure - so inhalation can be very harmful.

What's interesting about HF is that it is extremely corrosive despite being quite a weak acid (it's only about 2% dissociated in aqueous solution). I think the reason for this is that it hydrates much better than the other acids.

 

[Gokul43201]

It also reacts with the calcium in your bones to make CaF2, which is very insoluble in pretty much anything. That's not a good thing. The treatment for exposure is essentially a calcium supplement, I think.

Yes, typically calcium gluconate gel is used. Any lab that uses HF is required to have CGG easily accessible (I think it has now become mandatory...after someone died from multiple organ failure resulting from dropping a beaker of HF on his lap).