Preventing my next mistake

[Geo]

Sulfuric acid will precipitate lead sulfate which can be rinsed out with water. Other than that, I'm not sure. When you have solids in solution that will not settle, dilute the solution with water to lower the concentration of acid to help the solids settle faster. You can add water and then warm the solution and that sometimes help settle the solids. This is not always the case though as some solids settle better in colder solutions. It would probably be a good idea to try both and see which one works on the solution you have.

 

[butcher]

In the test, I proposed,
The purpose of sulfuric is to add a strong acid, (which can help to break the colloid with heat {this is not the purpose here}).

The main purpose for adding sulfuric acid here is to add a strong sulfuric acid with heat which will drive off the chlorides as gases, the sulfuric acid with a much higher boiling point will take the metals, in a chemical replacement reaction if you will, and to form base metal sulfate salts, (the gold is not soluble as a sulfate) and are not volatile as a sulfate during this heating process or in the incineration steps later, (gold is volatile as a chloride or with chloride salts at high temperatures).

Then with drying and incineration to drive off the sulfate as gases, the red hot heat is needed to drive off the sulfate, and with the red hot crushed powders exposed well to air to oxidize the base metals, basically changing sulfate metal salts to base metal oxides in this step of the process.

Leaving you with gold and base metal powders, oxidizing the base metals in the incineration process of red heat and air, or oxygen, which will help to put any tin involved in a better form, to be able to clean up your gold with the HCl boiling and washing procedure, to keep the gold from reforming a colloidal solution, when dissolved again, so that the stannous chloride test will be able to reduce the gold and detect it, if it is in solution...

 

[Geo]

Well yea, if you want to do it the correct way, but where's the fun in that? :lol:

Thank you butcher for straightening that up. I really wasn't referring so much to a colloid as just particles that take forever to settle. mas o menos, some drops I've had looked like a colloid.

 

[butcher]

Geo,
There just no fun when gold forms a colloid with tin, it is just mas o menos pain in the back side to deal with. :lol:

 

[jason_recliner]

I'd put this away until I understood it better. I still don't, though it's making more sense a few months on. It's time to clean up all my old messes.
Butcher, I've not been able to perform your colloid test on account of insufficient equipment to see it through to the end.

I've got a fair amount of dark greeny-brown-almost-black solution that I'm sure contains all sorts of tin and lead. The solution has been dissolving away any copper I put into it. Not knowing how much gold (if any) is in solution, I don't want to keep wasting copper unnecessarily. I've never had a positive stannous chloride reading (new batch should be ready tomorrow), which is not to say I would get one if it's colloidal. It's also quite diluted.

I just want it gone. I think I'm probably going to start treating it for disposal. But before I do, I've put about 5ml into a beaker and added about half again of sulphuric from an 8 year old bottle of battery acid, strength unknown. The reaction was quick and dramatic. BTW, it's about 25°C here this evening. 8) From the almost opaque darkness, a few seconds of milky white cloudiness then this.

Would that be most likely lead sulphate then?

 

[kurtak]

Lead sulfate is a white precipitate & settles fairly quickly

not sure what the greenish precip is (could be any number of things)

Kurt

 

[jason_recliner]

Yes, it was pretty fast. The powder is actually white under my clear green liquid. There's copper and ???? else still dissolved in there. The other green thing you see is my gloves!
It'll be put away again while I have a heap more reading ahead before I do anything more about it; I'm not as familiar with sulphuric processes as hydrochloric ones. But it sounds like a bit of sulphuric, and some ice, might be very useful to get some tidying up done.

 

[MarcoP]

Geo,
There just no fun when gold forms a colloid with tin, it is just mas o menos pain in the back side to deal with. :lol:

That's the second time I read about it in two days! Glad I really hard to eliminate tin before further processing, if I understand correctly dissolved tin (metastannic acid?) would help formation of colloidal gold.

 

[g_axelsson]

That's the second time I read about it in two days! Glad I really hard to eliminate tin before further processing, if I understand correctly dissolved tin (metastannic acid?) would help formation of colloidal gold.

Not exactly, tin(II) chloride (SnCl₂) is not the same thing as metastannic acid (H₂SnO₃)
Tin(II) chloride is the one we use to make colloidal gold from gold chloride.
Metastannic acid is the one that clogs the filters.

For more on metastannic acid : http://goldrefiningforum.com/phpBB3/viewtopic.php?f=49&t=17049

Göran

 

[MarcoP]

That's the second time I read about it in two days! Glad I really hard to eliminate tin before further processing, if I understand correctly dissolved tin (metastannic acid?) would help formation of colloidal gold.

Not exactly, tin(II) chloride (SnCl₂) is not the same thing as metastannic acid (H₂SnO₃)
Tin(II) chloride is the one we use to make colloidal gold from gold chloride.
Metastannic acid is the one that clogs the filters.

For more on metastannic acid : http://goldrefiningforum.com/phpBB3/viewtopic.php?f=49&t=17049

Göran

At the end of the 6th paragraph in the original post he mentioned sodium nitrate but I misinterpret it as he didn't add any. In that case I was probably right I hope :lol:

Thank you for the explanation and the link!

 

[pu_239]

It appears the situation was handled, when i saw the original vessel, the first thing that came to mind was to add more H2O2. It appeared the reaction came to a screeching halt. as butcher said, you can be driving off HCl with heat, i cover my beaker with a watch glass to minimize evaporation, i also run it at a lower temperature, around 50-60 degree's C.

The reaction can reach equilibrium, meaning it will pretty much stop upon observation. According to le chatelier principle, the only way to get the reaction going again is to take out some CuCl2/H2O, or add some Copper/H2O2(oxygen source)/HCl.

Cu(s) + H2O2 + 2HCl --------> CuCl2 + 2H2O

If you evaporate off some HCl, that will cause the reaction to go backwards preventing the leaching. Heating in a open container isn't the best idea. Adding some ice to the watch glass that is on top of the beaker will help(but i know it's a bit too much to be dealing with). This would hopefully help the HCl condense back in to liquid form and drop down in to solution.

Adding the bubbler helped add an oxygen source, which drove the reaction forward. It accomplishes the same thing as adding a bit more H2O2. From my chemical experience, i only refined gold once, but what i have to say is try to understand the reactions and what's going on before you fully start. You can run in to situations(like you did) you need to know how to handle them. I ran in to a few obstacles myself, but i knew how to handle them from my past experiences. There maybe no one to help you when you're on your own.

ETA: That white ppt that you think is Pb(SO4)... what if it is, what if it isn't, how does it effect your gold recovery? Whatever it is(I think it's PbSO4) i don't see it having any bearing on your gold recovery. Just filter it and move on.

 

[jason_recliner]

At the end of the 6th paragraph in the original post he mentioned sodium nitrate but I misinterpret it as he didn't add any. In that case I was probably right I hope :lol:

Thank you for the explanation and the link!

You're right, there was no sodium nitrate used at that point. I was referring to my first batches where I'd impatiently overloaded with nitrate, to the point where working stannous chloride was unable to detect even small federal reserves of gold.

 

[jason_recliner]

It appears the situation was handled, when i saw the original vessel, the first thing that came to mind was to add more H2O2.
...
Adding the bubbler helped add an oxygen source, which drove the reaction forward. It accomplishes the same thing as adding a bit more H2O2.

The major difference of course is that adding H2O2 can start dissolving gold which will cement as dust, whereas the bubbler will leave it as foils.

try to understand the reactions and what's going on before you fully start. You can run in to situations(like you did) you need to know how to handle them.

I had a plan from start to finish, but do understand it's only the expected obstacles that cause trouble. Once they are expected, they'd be part of preparation. Your chemistry education puts you in an excellent position in this field.

ETA: That white ppt that you think is Pb(SO4)... what if it is, what if it isn't, how does it effect your gold recovery? Whatever it is(I think it's PbSO4) i don't see it having any bearing on your gold recovery. Just filter it and move on.

It doesn't affect my recovery. This will not become a recovery unless I happen upon a positive indication. I'm just trying to gain a bit of experience with a small sample of my waste.

Think of it more as a post-mortem. Learning from others' mistakes is invaluable. But there's no excuse for not learning from your own.

 

[pu_239]

It appears the situation was handled, when i saw the original vessel, the first thing that came to mind was to add more H2O2.
...
Adding the bubbler helped add an oxygen source, which drove the reaction forward. It accomplishes the same thing as adding a bit more H2O2.

The major difference of course is that adding H2O2 can start dissolving gold which will cement as dust, whereas the bubbler will leave it as foils.

try to understand the reactions and what's going on before you fully start. You can run in to situations(like you did) you need to know how to handle them.

I had a plan from start to finish, but do understand it's only the expected obstacles that cause trouble. Once they are expected, they'd be part of preparation. Your chemistry education puts you in an excellent position in this field.

ETA: That white ppt that you think is Pb(SO4)... what if it is, what if it isn't, how does it effect your gold recovery? Whatever it is(I think it's PbSO4) i don't see it having any bearing on your gold recovery. Just filter it and move on.

It doesn't affect my recovery. This will not become a recovery unless I happen upon a positive indication. I'm just trying to gain a bit of experience with a small sample of my waste.

Think of it more as a post-mortem. Learning from others' mistakes is invaluable. But there's no excuse for not learning from your own.

Yes I understand your concern with H2O2, but I didn't see a problem because that's how you started out. My view is you just ran out of an oxygen source.So you're not really "adding" more H2O2 than what you started with. I had no problem with HCl evaporating, my solution was acidic when the reaction was done.

That's a good thing to do, start with small samples to gain experience, that's where i messed up. I bought 10lbs of ram and processed it all. I was looking for profit, which i found out I lost money. I wish I would have started smaller to know what to expect. Yes it's obviously good to learn from your own mistakes. I learned from a few of mine. I know a few things I would do differently if i process ram again.

 

[butcher]

I wish I had back a lot of the material I was learning on, when I was first learning.
That may be one reason I keep pushing study over experimentation, when beginning to learn this.

Study can prevent a lot of mistakes.
To prevent my next mistake I study.