How to roast

[goldscraphobby]

Hi,
I have gone through the search and did not find any specifics on roasting.
I have gold stripped using both HCL (AP) & Nitric and want to combine them to refine more
Not sure how to actually perform the roast.
Do I put it all into a stainless steel pot
Can I put the pot on a propane camping stove or heat from above with a torch?
How do you know if its "roasted" enough?
Thanks

 

[Geo]

Cast iron is better for roasting in my opinion. It is less likely to develop a hole due to the acids. Roast by bringing the material to a dull red heat that you can see in low light. This should destroy any acids or organics.

 

[FrugalRefiner]

I like stainless steel, but not a pot. I prefer a frying pan. Fumes can escape easier, and oxygen from the air can help oxidize base metals.

Dave

 

[goldscraphobby]

Thanks,
Is a propane stove sufficient to roast? Or will I need to also use a propane tourch from above
I only have propane

 

[FrugalRefiner]

Let's go back to the original question. You have "gold stripped using both HCL (AP) & Nitric and want to combine them to refine more". What is your next step in refining them more? I ask because if your next step is to dissolve your gold in AR or a similar solvent, there's no need to roast or incinerate at all.

Dave

 

[goldscraphobby]

Hi Dave,
I want to wash it all with HCL a couple times to make sure all base metals are gone then HCL & Clorox & drop.
Its a mixture of large & small foils and pieces. After dropping I'll add it to the rest of my gold powder

 

[anachronism]

Hi there

I noticed you were using Nitric to perform the initial strip on some of the material. As that's the case why don't you just use AR to do the dissolve?

Jon

 

[goldscraphobby]

I have limited nitric, expensive and hard to find. What I have I'm using it to lift the gold off some plated housings. Also never used AR, so I would have another process to learn and keep track of.
I'm comfortable using muratic, AP & HCL/CL
The pictures below is what I have from the nitric, want to be able to finish using HCL

 

[Geo]

You can do a prolong soak in a strong base to remove the acid residue. Use sodium hydroxide or even baking soda. Rinse well before moving to the next step.

 

[goldscraphobby]

That is even better, baking soda is easy.
Thanks

Eventually I'll get to a button

 

[UncleBenBen]

Wait, why would you want to kill some acid that can help dissolve the foils?

 

[chuckgambale]

I'm pretty sure he has a lack of nitric acid. Also I think he is trying to remove as much base metals as possible before dissolving in HCL and bleach. His theory is sound (crap in crap out), but in this case he can probably add the two sources of foils together add some excess hcl and it will probably dissolve just from the excess nitric on the foils. No roast needed. A second drop will get you very high purity especially if you look up Harolds wash method and use it.

 

[anachronism]

Whilst I understand the point about Nitric being hard to come by, given that the amount required to dissolve that gold will be a small fraction of what you used to strrip the material in the first place I don't understand the logic for not using it.

Using AR isn't an onerous learning curve provided you follow the advice about it all over the forum. You could put those foils in HCL and add literally a few drops of Nitric and they would be dissolved.

 

[Geo]

You can estimate nitric acid usage on clean foils as 1ml tech grade per gram of dry foils.

 

[upcyclist]

If I suspected I had significant silver in there (note that this is more likely in recovering from jewelers scrap than e-scrap), I would roast the leftovers from the chloride processes to destroy the chlorides, then combine, then use nitric to free the silver, then AR. But that's the main case where I would roast.

If I thought there might only be trace or no silver, I'd just go straight to AR (or Poor Man's AR, etc.) with both batches and filter off any formed silver chloride.

The most common reason for roasting is to remove chlorides before they cause problems, and silver chloride can be a problem if you prefer to keep it out of that state. If chlorides won't cause you problems (because your next step is to deliberately combine HCl & HNO₃), then you don't need to roast.

 

[goldscraphobby]

Thanks everyone for the inputs. So I don't have to have another process going I will neutralize the gold I lifted using nitric with baking soda (Its already been rinsed several times with water so I wouldn't expect too much nitric residue). I can then take that and continue with my normal cleaning and dissolving with HCL & bleach.

I can look into AR but at this time I am setup just for AP (couple buckets going) and the one nitric bath for the large housings.

 

[upcyclist]

Thanks everyone for the inputs. So I don't have to have another process going I will neutralize the gold I lifted using nitric with baking soda (Its already been rinsed several times with water so I wouldn't expect too much nitric residue). I can then take that and continue with my normal cleaning and dissolving with HCL & bleach.

Again, no need to neutralize it, you're just going to acidify it again. HCl needs an oxidizer to dissolve gold--most use nitric acid, others use bleach. Any nitrates left over in your one batch will only help to dissolve the gold, alongside your bleach.

Edit to add: And neutralizing won't actually get rid of your nitrates. It'll just kill the free acid, which is the H side of the formula.

 

[anachronism]

As an aside I have never roasted anything in 6 years of refining. Oh apart from my right hand occasionally when I've moved a torch too vigorously....

 

[goldscraphobby]

OK, Sorry I think I didn't explain what I'm trying to do & need to start over.
What I have is some gold stripped off housings that may still have small amounts of the base metal attached. This was removed using a dilute nitric.

What I want to do now is put this into my AP to remove the minor remaining base metals. This, along with my other gold from AP processes, will then be washed and then the clean gold dissolved in HCL/Bleach.

I have several buckets of AP with various stages of product in it. I have the one setup with dilute nitric. I do not want to add another process such as AR- at this time.
My AP setup is going good and will remove the small amount of base metal left.

What I am looking to do is remove any nitrates that may be on the gold stripped in the dilute nitric bath before I put it into the AP

I thought I needed to roast it before I can go to AP. If so how to roast.

 

[anachronism]

Hi there

Wash your flakes in hot HCl and keep your waste HCl for dropping later if it tests positive for gold. Then water wash and then HCL wash again till it's clear.

Keep your wash liquors and drop those with smb to be sure there's no gold. Remember test everything ok?

Jon