[SteveE]

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.

[SteveE]

This is a picture of the two specimens. I simply want to remove some of the quartz surrounding the gold.

[Enthalpy]

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.

[SteveE]

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.

[wildfyr]

I'm sorry Steve, but do to what you are asking is going to require a source of fluoride ions.

[SteveE]

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

[Corribus]

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.

[Enthalpy]

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.

[SteveE]

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.

[SteveE]

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

[Corribus]

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.