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hydrofluoric acid

Posted by Albert Russ  
avatar Re: hydrofluoric acid
April 11, 2012 01:07PM
Have you looked into leaching your fines with cyanide?

Rock Currier
Crystals not pistols.
M. Dante
Re: hydrofluoric acid
April 11, 2012 03:11PM
I guess I should share my background in HF, at least for safe practices. Like has been said before, HF is a very small atom, and will rapidly diffuse across the the skin, as it does so, it will continue to yank Ca+ from the body. Both muscles and nerves need the calcium ions to function, so this is obviously a very bad thing to happen. As this happens, it will stun the nerves as it moves, HF is painless spills, at least for a little bit. After a while you will get a horrific burning sensation, and the wound will begin to look like a pit or a bed sore. If the spill is large enough, it can cause major health issues. Either way, the would will be very painful and slow to heal. It will also be prone to infection.

We can take advantage of the fluorine ions nature to protect ourselves. When F- comes in contact with Ca++, it will precipitate as CaF2, which is fairly insoluble and harmless. Unlike the strong acids, such as HCl and H2SO4, HF is not fully ionize din solution. This means that throwing some baking soda on it will not neutralize it fully. In addition, NaF is not exactly friendly. Instead, have a solution of Calcium Chloride on hand, or any other highly concentrated source of Ca ions. Use this on spills, the Calcium will harvest the F-, and remove it from solution, which will shift the equilibrium of the HF:H+,F- in solution. You want to kill as much of the F- as possible, bind it up and get rid of it. When you shift the equilibrium, you can do this, carbonates will not react with HF fast enough for this to be useful or safe. Keep 2 bottles of calcium gluconate on hand as well. This is for the worst case scenario, that you spill some on yourself, use one bottle to saturate a roll of gauze and the other right next to you. Use this on any suspected spills without hesitation, remember that HF is painless.

Gloves and protective clothing is important, make sure your respirator is rated for HF. I would find a good, reliable respirator as well, don't go for the walmart special on this one. HF will diffuse across the lung very quickly, and good luck hitting your lung with Ca++ to protect it. HF gas will also come off the solution HF can diffuse across most gloves, so again, do your research and don't skip out on good safety equipment. Wear clothing that is protective, but also shows up liquid spills quickly. Above all, common sense is your best friend.
M. Dante
Re: hydrofluoric acid
April 11, 2012 03:28PM
All in all, HF can be handled safely with experience. Etching the quartz with HF is very simple, simply let the silica sit in the HF for a while. I would not suggest a glass container for this purpose. The stronger the acid,the more aggressive the acid will be. Three percent is the most common solution for etching, but I would experiment with both concentration and etch time. Good luck with the project. I hope all of this fear mongering has not put you off.
Re: hydrofluoric acid
April 12, 2012 12:09AM
And if you do spill enough on yourself that you have to go to the hospital (do you know how much that would be?), you're probably going to encounter a medical staff that's not familiar with dealing with this situation.

The safety protocol for HF related hospital visits at school was to take the calcium gluconate gel with you and insist to the triage nurse that you needed to get to a shower immediately if they didn't understand the urgency of the situation.

In fact, personally I would have someone call ahead so they know you're coming. Diluted HF exposure is one of those emergencies that doesn't seem like it is.
Re: hydrofluoric acid
April 12, 2012 08:04AM
Hi, Did I read it right, can you use sodium bicarbonate to neutralise HF and can get rid of it safely? Rolf
Re: hydrofluoric acid
April 12, 2012 01:46PM
No, sodium bicarbonate is not a good neutralizer for HF. Calcium chloride is much safer. On skin, use calcium gluconate gel.
avatar Re: hydrofluoric acid
April 13, 2012 05:11AM
Would you mind if I use most of what you say about using HF and put it in my article about cleaning quartz. Will give you credit, or course.

Rock Currier
Crystals not pistols.
M. Dante
Re: hydrofluoric acid
April 16, 2012 03:25AM
Of course you can

Good luck
Re: hydrofluoric acid
April 23, 2012 01:02PM
I've been using HF in specimen processing for decades with no ill effects.

Nothing does what HF can do.

However, I would never recommend its use by the general public.

If you must use HF be sure to tape a tube of calcium gluconate gel from Calgonate Corp of Rhode Island onto your wall. Not in a drawer somewhere.

Also use an eyeshield and plastic tongs during specimen transfer. You will lose your appetite if you see what a drop of HF will do to an eyeball.

If you use rubber gloves use only very heavy duty re-enforced ones. Thin gloves always have pinhole leaks, especially if they have been used to pick up quartz.

I haven't read all of the posts. Has anyone mentioned HF's more friendly sister, ammonium bifluoride ? It removes silica scum very nicely and attacks feldspar and fingertips with less aggression.


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