Situations to Avoid--The Safety Thread

[Lou]

Your first mistake was graphite. Glassy carbon is the thing to use if you're going to use carbon, but these are done usually in Pt95Au5 crucibles, which are quite resistant to alkalis. I run mine at 1000 C. Mostly useful for aluminaceous material. I also do a few Na2O2 fusions a week (20-30) in Zr crucibles, though alot of people use nickel for reasons of economy.

Second mistake was that you poured a melt like that (basically molten alkali oxides and glasses) into a dilute sulfuric acid solution in a glass beaker. You should have used a (poly)methylpentene beaker. Basically the shock wave from acid-base reaction at high temperature, steam formation, etc. is what destroyed the beaker. Thank goodness you had PPE on when conducting this.

If you have a sonicator, you can wait until the reaction is cool and then go from there. The issue is if you conduct fusion in graphite in air, the graphite will oxidize and particles will come off during sonication.

 

[chemtag]

Your first mistake was graphite. Glassy carbon is the thing to use if you're going to use carbon, but these are done usually in Pt95Au5 crucibles, which are quite resistant to alkalis. I run mine at 1000 C. Mostly useful for aluminaceous material. I also do a few Na2O2 fusions a week (20-30) in Zr crucibles, though alot of people use nickel for reasons of economy.

Second mistake was that you poured a melt like that (basically molten alkali oxides and glasses) into a dilute sulfuric acid solution in a glass beaker. You should have used a (poly)methylpentene beaker. Basically the shock wave from acid-base reaction at high temperature, steam formation, etc. is what destroyed the beaker. Thank goodness you had PPE on when conducting this.

If you have a sonicator, you can wait until the reaction is cool and then go from there. The issue is if you conduct fusion in graphite in air, the graphite will oxidize and particles will come off during sonication.

I am aware of the graphite crucible problem (i.e. its not great for this type of fusion), but without a Platinum (or Pt/Au) crucible, I have to work with what I have. And for now, its just a matter of practice and learning these pyrometallurgy techniques. If the little graphite bits contaminate my sample, that is fine. I usually just do a quick centrifuge before loading the digested fused sample into the ICP. Things may change in the future, but I can't force the powers-that-be to buy a 2-3k crucible for a niche analytical technique (for our operations).

Do you think there is any concern about my pour rate? Or my molten-sample mass versus the mass of water+acid I was pouring into? Could I have poured the stream onto the side of the beaker and caused problems? Or is it your opinion that had I done everything exactly the same BUT been in a Teflon (or polymethylpentene) beaker, everything would have been totally fine?

 

[Lou]

Seeing as a 1 liter teflon beaker is probably a third the price of the crucible (which I can happily turn for you, should you want one), you will want to use something cheap. Even HDPE is fine for this application. My advice would be to pour into a mold, which again are usually PtAu. In your case you can use graphite. Cover it over until it cools with another piece of graphite. Then demold and break it up in a mill or good mortar and pestle. You can add a small amount of LiCl to help it not stick so much.

Generally speaking, molten basic materials and water is a bad mixture and you are hearing this from someone who thought it was a good idea to pour molten KOH slag mixture into water once. Not a good idea. You have to remember that it's not just the thermal mass of the fusion, it's also the heat of the reaction that goes ballistic. I can put a beaker of pyrex in a 5 gallon bucket, put a little dish soap, and make about 300 g of gold shot without break the glass. Sure gold is a better conductor, but the real difference is there's no chemical reaction when it hits the water.

Even making Adam's catalyst (PtO) from KNO3 + (NH4)2PtCl6, it is very scary pouring that mixture into the trough!!

 

[cuchugold]

I might need to get involved with Fluorine, and HF, which I have avoided all my life. I'd love to read detailed safety measures about that.

 

[anachronism]

I might need to get involved with Fluorine, and HF, which I have avoided all my life. I'd love to read detailed safety measures about that.

Sure that's easy. Don't even think about using HF. Park the idea and forget you even thought it.

 

[cuchugold]

Anach: You seem to be the most recent resident master of what cannot be done.

Here's a tip: HF readily vaporizes a quartz matrix. Yes, it is corrosive and nasty.

 

[Yggdrasil]

Well!
HF is a substance most experienced refiners will not touch if they don't have to.
And the agreed upon pratice, is to walk away if there is no workaround.
Simply because of its toxicity and bad interaction with living or dead tissue.

When that is said, there are people using it still for a number of reasons.
I believe paleontologists and geologists, use it to dissolve the matrix in which objects they want/need is to be liberated from. Just fill in the blanks.

It is not my decision, but maybe we need to give HF a bit of the recent "CN" treatment.
If we assume people are going to use it anyway it may be more productive to give stern warnings and then inform what kind of safety coniderations to take.

Like this: Stay away, stay far away. If you still are going on, do this and this only.

Like I said, not my decision, just my 2 cents.
And I see no reason to use it my self.

 

[cuchugold]

Proposed pilot process is to dissolve quartz, and re-cycle SiF4 vapors back into HF, as safely and cleanly as possible, avoiding free Fluorine, if at all possible. HF is nasty and dangerous. It is what it is. It breaks a 95%+ quartz matrix down to the atom level to free or combine with other metals present. If it can be regenerated easily, there may be an economical gain to be made.

 

[Lou]

Proposed pilot process is to dissolve quartz, and re-cycle SiF4 vapors back into HF, as safely and cleanly as possible, avoiding free Fluorine, if at all possible. HF is nasty and dangerous. It is what it is. It breaks a 95%+ quartz matrix down to the atom level to free or combine with other metals present. If it can be regenerated easily, there may be an economical gain to be made.

Obviously by now you know I work with HF. Lots of it, I guess.

I am not sure it will be cost effective. Also, it will not easily be recycled in the field. Any SIF4 (which is very nasty compound, I only make it to free samples of silicon), hydrolysis of this will make HF but any excess HF in gas stream will give H2SiF6 rather than HF itself.

Unless you found large nuggets of gold in quartz matrix, this is not going to be safe or tenable financially (not at $0.45/lb, which is 49% HF price in bulk).

 

[cuchugold]

As usual, thanks Lou.

So simple hydrolysis will produce either HF or H2SiF6?. Both of these are corrosive to SiO2 and can be recirculated into the "leaching vessel" perhaps?.

It does not have to be a big vessel or initial quantity of HF, if 95%+ of it can be recirculated. This can perhaps keep the hazard relatively small, with some emergency scrubbing trap?.

The deal is this: Some "garbage tailings" assay X, very small with standard fire assay. If same sample is leached with HF and then fire assayed, it gives nearly 15 grams gold per Ton. Reading Deano's posts and other things I found here and there, I have to reach the conclusion that it is superfine gold entrapped in the particles.

 

[anachronism]

Anach: You seem to be the most recent resident master of what cannot be done.

Here's a tip: HF readily vaporizes a quartz matrix. Yes, it is corrosive and nasty.

You've got to be kidding mate. 8)

If you'd joined the forum when I did in 2012 you'd have struggled to discuss anything but Hoke's accepted methods without being frowned upon. I used to get in all kinds of trouble for suggesting different things as did many others.

The reasons you originally steered clear of using HF are all still there. They haven't changed at all. If you're thinking of using HF on ore, then do you know how the HF is going to interact with all the different compounds that could be present because if you don't then you should.

One drop of HF on your skin note one drop and you're in trouble. Now I've done a fair bit of acid refining over the years and I can't remember a single day where for one reason or another I've not got a drop of acid either on my clothes, my arms, or elsewhere in some form or another. I'm careful, and I wear PPE but it happens. Certainly more so when you get confident with a process. Now that's a failing in me I accept that however you do not have that room for margin with HF.

For the record I love new ideas, I thrive on finding improvements to processes and ways to improve yields for less time invested. Please don't criticise me for trying to save your ass because that's literally what I was trying to do. No offence taken, I'm just setting the record straight. 8)

Jon

Edit I re-read the last bit of your comment. It's not how corrosive HF is, that presents the problem. It's what it does inside your body when you get it on your skin even if you wipe it off.

Take a read of this and let me know how you feel about using it. https://web.utk.edu/~ehss/training/has.pdf

 

[FrugalRefiner]

If you'd joined the forum when I did in 2012 you'd have struggled to discuss anything but Hoke's accepted methods without being frowned upon. I used to get in all kinds of trouble for suggesting different things as did many others.

Jon, cuchugold actually joined the forum on May 26th, 2010 as HAuCl4. He forgot his password and reregistered as cuchugold.

Dave

 

[jimdoc]

If you'd joined the forum when I did in 2012 you'd have struggled to discuss anything but Hoke's accepted methods without being frowned upon. I used to get in all kinds of trouble for suggesting different things as did many others.

Jon, cuchugold actually joined the forum on May 26th, 2010 as HAuCl4. He forgot his password and reregistered as cuchugold.

Dave

Maybe when members do that, it should be required to be in their signature what their former identity was.

 

[anachronism]

If you'd joined the forum when I did in 2012 you'd have struggled to discuss anything but Hoke's accepted methods without being frowned upon. I used to get in all kinds of trouble for suggesting different things as did many others.

Jon, cuchugold actually joined the forum on May 26th, 2010 as HAuCl4. He forgot his password and reregistered as cuchugold.

Dave

Ok cheers that's good to know Dave. In that case he'll remember exactly what I was referring to 8)

 

[snoman701]

I can tell you that out of all of the chemicals I have worked around, HF is up there as one of the scarier ones.

The fact that the pain of exposure is delayed just makes it that much scarier. You get most acids on your hands and you know pretty quick they are there.

What I hate is that after I've worked in gloves for a while, I get sweaty hands...and at that point I don't know if I've got a leaking glove or a broken glove. If it's a strong acid, you'll feel it...if it's HF, that pain could be delayed a while. And if you look at the average amount of "hand sweat" wetness, it is going to be enough HF to land you in the ICU at minimum.

I accept that at some point I'll have to find a procedure for frosting stones, but I also will not do this until I have a purpose built containment unit....and it will NEVER be a large amount at a time.

 

[cuchugold]

Yes. Thanks guys. It's too dangerous. Forget about it.

 

[JoeyJoystick]

I am not a gold refiner, but have been working in the oil industry for 35 years of which 15 in South-East Asia. In this sense I am no stranger to chemicals and their dangers. Not an expert either, but I have NEVER had an accident at work nor did the people who work with me or for me. Safety is obviously always an issue and here, much like everywhere else in the industry, slogans are used to make it easier for people to remember safety. Far from specific, but still helpful slogans I remember:

- Better safe than sorry.
- Proper Preparations Prevent P-I-s-s Poor Performance. (Apologies beforehand, but I am hoping this is allowed due to the context…)
- Kiss; Keep It Simple Stupid. Very important! When you keep it simple it is more easy to see the safety traps.
- Good tools are half the job.

And not an expression but still valuable informative one liners:
- Everybody can stop work (or stop others from working) for any safety issue.
- Be very careful and aware of any pressurised gas or possible pressure build-ups.
- Store chemicals properly.
- Keep incompatible chemicals separated from each other by a fair distance.

When I remember more I will add accordingly. If anyone else wants me to add something just send me a PM.

Joey