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Topic: HF Acid Substitute  (Read 9266 times)

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Offline SteveE

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Re: HF Acid Substitute
« Reply #15 on: January 17, 2018, 02:53:49 PM »
Polypropylene and polyethylene are cheap and they resist many acids and bases, but not heat. +80°C would already be a lot.

Stainless steel should resist NaOH and KOH but not HF. Some cooking sieves are made of it and they resist heat.

The answer to slow etching is crushing to a fine powder. Ball mill?

I want to remove quartz from a couple gold in quartz specimens in situ to expose more gold. Not put the specimens into a ball mill and grind to a fine powder.

Tried to take a couple pictures but I couldn't post them because the files are too big. I'm not quite sure what to do.

Offline SteveE

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Re: HF Acid Substitute
« Reply #16 on: January 17, 2018, 03:25:45 PM »
This is a picture of the two specimens. I simply want to remove some of the quartz surrounding the gold.

Offline Enthalpy

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Re: HF Acid Substitute
« Reply #17 on: January 18, 2018, 11:58:13 AM »
A fine powder will be dissolved more quickly because there is less thickness to go through. The standard path to fine powder is a ball mill.

Offline SteveE

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Re: HF Acid Substitute
« Reply #18 on: January 18, 2018, 12:04:04 PM »
I understand that but I would have to destroy the specimens if I were to put them in a ball mill. What I'm trying to do is dissolve the quartz from the gold leaving the gold intact thereby creating a 3D web of gold.

Offline wildfyr

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Re: HF Acid Substitute
« Reply #19 on: January 18, 2018, 01:42:14 PM »
I'm sorry Steve, but do to what you are asking is going to require a source of fluoride ions.

Offline SteveE

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Re: HF Acid Substitute
« Reply #20 on: January 18, 2018, 03:06:06 PM »
I am assuming that acidifying sodium or potassium fluoride with HCL acid will produce HFL acid. What would be needed to produce one liter? And what strength HFL would this produce?

Thanks

Offline Corribus

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Re: HF Acid Substitute
« Reply #21 on: January 19, 2018, 12:05:58 PM »
You can use powdered CaF2, which I believe works pretty well to form HF in situ in the presence of concentrated sulfuric acid.

Do be careful, however. This chemistry is fairly hazardous and proper waste disposal can be challenging.
What men are poets who can speak of Jupiter if he were like a man, but if he is an immense spinning sphere of methane and ammonia must be silent?  - Richard P. Feynman

Offline Enthalpy

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Re: HF Acid Substitute
« Reply #22 on: January 21, 2018, 06:21:17 PM »
Silica is soluble in molten KF-KCl around 1000K. This could go faster that the acid's action.

I wonder: is HF better than KF to dissolve silica in water?

Handling HF: I hope this would be done near to the next shower with unlimited water supply and near to the next hospital. That is, not in the wildness. HF is not just any acid.

Offline SteveE

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Re: HF Acid Substitute
« Reply #23 on: January 22, 2018, 09:32:17 AM »
Silica is soluble in molten KF-KCl around 1000K. This could go faster that the acid's action.

I wonder: is HF better than KF to dissolve silica in water?

Handling HF: I hope this would be done near to the next shower with unlimited water supply and near to the next hospital. That is, not in the wildness. HF is not just any acid.

Don't worry. I have plenty of experience working in a chemical plant as well as a lab technician.

Offline SteveE

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Re: HF Acid Substitute
« Reply #24 on: January 25, 2018, 05:07:20 PM »
Hello Everyone

I have one last question. As you know, I plan to suspend the gold and quartz specimens in HF acid using Teflon tape.

Can anyone recommend a certain type of clear plastic or glass beakers I can use that are resistant to HF acid? The idea is to suspend the specimens in HF acid using Teflon tape so I can see what's going on without having to constantly picking them up and observe them.

Thanks

Offline Corribus

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Re: HF Acid Substitute
« Reply #25 on: January 25, 2018, 05:56:48 PM »
Most polyolefin plastics have good chemical resistance - polypropylene or HDPE plastic would probably be OK. Teflon would be best, particularly if you plan to do any heating, but expensive. Don't use glass or metal, although you could use those if they have a thick chemical resistant (plastic) lining.

I suggest testing any container with a little bit of your acid first to be sure.
What men are poets who can speak of Jupiter if he were like a man, but if he is an immense spinning sphere of methane and ammonia must be silent?  - Richard P. Feynman

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