"Roasting" temperature

[goldscraphobby]

Hi,
I have some gold I recovered using nitric and before I go to HCl (all my other gold used AP to remove the base metals) I'm supposed to "roast" the nitrates.
What temperature am I supposed to reach in the "roast"? I was able to find the temp to "roast" at.
I have an old toaster oven, can I put the gold in that at 450/500 for a couple hours, do I have to heat it with a torch?
Thanks

 

[Martijn]

Which metals do you expect to remove with the HCL?
And what did you start with to end up recovering gold with nitric?
A roast and HCL may not be needed and go straight to AR. You can drop lead for instance with some sulfuric acid and wash with HCL after dropping with SMB.
But most base metals would have been consumed by the nitric I think.

Or a couple hot/boiling water washes may do the job?

Don't know much about roasting off nitric. Can't help with that. Sorry.

You could lose gold if traces are left when washing in HCL, obviously the reason you want to roast.

Some more info about the starting material, the process and the end goal could help.

Martijn.

 

[Geo]

Nitric acid decomposes (boils) at 181°F. So dull red heat is about four times that hot. It should stay at dull red until all of the material has been exposed to the red heat.

::C ----- ::F ---- Color

400 -- 752 -- Red heat, visible in the dark
474 -- 885 -- Red heat, visible in the twilight
525 -- 975 -- Red heat, visible in the daylight
581 -- 1077 - Red heat, visible in the sunlight
700 -- 1292 - Dark red
800 -- 1472 - Dull cherry-red
900 -- 1652 - Cherry-red
1000 - 1832 - Bright cherry-red
1100 - 2012 - Orange-red

 

[goldscraphobby]

Sorry should be been a little more clear.
I want to take the gold foils I got from recovering in nitric, do some extra cleaning in HCl and dissolve them in HCl & Cl.
I have limited nitric and want to clean/refine using HCl. I do not want to get involve in AR.
Thanks

Geo, Thanks for the info, Seems like I can just put them into my junk toaster and bake them for several hours at 450 (mix once and awhile) and be good to go.

 

[g_axelsson]

This seems a bit backwards to me. If you are limited in nitric you should use HCl and copper chloride for the recovery and just add small amounts of nitric acid at the end to dissolve the foils. This would be slower than using nitric for the recovery.

To dissolve the base metals with nitric probably used up 100 times more nitric than it would take to do the last foils in aqua regia. You could even use some of the left over nitrate waste and mix it with HCl to make aqua regia. The resulting gold chloride would have some copper and nickel in solution but precipitating the gold with SMB or copperas would create a decent enough gold powder that with some boiling in HCl would be acceptable.

Göran

 

[goldscraphobby]

Hi,
I used nitric because I have some material that was gold on aluminum (very large Al housings), this recovered the gold. I thought this way would have less waste.

Everything else I have done used AP, HCl & Cl. So I have this gold recovered with Nitric and everything else is with HCL.

Was I backwards about wanting to limit processes by just doing this (roasting) the material from nitric so I can keep everything to one process?

 

[kurtak]

If I got this right - you recovered "some" foils using nitric - then you also recovered "some" foils using AP

You now want to dissolve "all" of those foils together

Your question is - "do I need to roast the foils from the nitric process (to get rid of the nitric) before dissolving the foils from the two different processes"

The answer is NO

Wash the acid out of both processes as best as possible - after washing - put all foils in your beaker cover with HCL - any "small" amount of nitric left from washing those foils will go to work at dissolving the foils - use heat (hot plate)

One of two things will happen (1) the nitric will dissolve all the foils - or - (2) only some of the foils will dissolve

If all the foils dissolve - you may then still have free nitric - de-nox with sulfimic - or urea - or copper --- Edit to add; - or use it to dissolve more gold until it dissolves no more gold

If only some foils dissolve - start adding bleach till the rest of your foils are dissolved (or add "small" amounts of nitric till rest of foils are dissolved)

Drop you gold as you normally do

Kurt

 

[g_axelsson]

Gold plated on aluminium with a barrier layer of nickel or copper is a perfect way to use nitric. I apologize to just assume that you had gold plated on copper. My bad.

Kurt is correct, follow his advice.

Göran