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Williamjf77

Well-known member
Joined
Oct 30, 2018
Messages
138
Hello everyone, I have a little issue processing regular pentium gold cap ceramic cpu’s In AR.

I smashed then lightly torched then put in a beaker with hcl then heated, once I got up to temp I added nitric in 2-3 ml doses and everything was going fine then after a while the solution precipitated a green powder and stopped reacting with nitric additions. I then added more hcl and still no more reaction.So I took it off the heat and let it cool. The solution was pretty dark but I poured off some and noticed the gold pins still there, albeit pretty flimsy.

I tested with stannous and got a streak of black but not a normal looking result so I questioned the stannous. Made new batch and let everything sit over night.

Today I filtered the whole solution and retested with stannous and got a negative. In the filter is a green / yellow precipitation.

Should I proceed with a fresh AR on the remaining solids or is there gold in the green pea soup looking powder?

I can add some pictures tomorrow, thanks
 
The precipitate looks like a byproduct of the tungsten manganese conductors embedded in the ceramics. You would probably not be able to dissolve it again. You could probably dissolve any gold in the precipitate with AR and filter it off.

I would restart with fresh AR, stannous is probably correct in that there is no gold in solution. Any dissolved gold has probably cemented out on remaining base metal. Some might be in the yellow precipitate, try a small sample with AR and then test with stannous.

By the way, you should have a gold standard solution prepared so you can test the function of your stannous. Take a couple of the pin gold foils and dissolve, dilute it to a pale yellow concentration and test your stannous.

Göran
 
Thanks goran, actually after I took the pics I took some gold powder I had and made a standard to test the stannous.

Turns out my old stannous was still good but both bottles actually either blew off the dropper bulb or eroded it, I’m not sure, it is pretty cold here in New England, maybe that had something to do with it or maybe the cheapo glass dropper bottles.

Tomorrow I will try fresh AR on the chips and the precipitate separately and I’ll update the results.
 
Good idea William.

Effectively you've run out of Nitric and not run the reaction through to its conclusion. I'm sure it's a bit of a daft comment but I call those "hedgehogs" and until all those have gone you haven't finished the recovery dissolve.

One thing I would add to Goran's post is that you probably have gold powder lurking within the precipitate. It precipitates out if you have base metals present and stop the reaction early, or run out of oxidant/HCl. I would suggest doing the whole lot again including the precipitate in a good hot solution to reclaim all the gold.

Thanks for the pictures, they helped a great deal. 8) 8)

Jon
 
Ok well here is another question, if the AR solution was out of hcl when I added more nitric would the reaction resume after adding more hcl? Or would cemented metals stop the reaction from resuming.

In other words if there is no free Cl but excess nitric would the reaction resume after adding more hcl?
 
Williamjf77 said:
Ok well here is another question, if the AR solution was out of hcl when I added more nitric would the reaction resume after adding more hcl? Or would cemented metals stop the reaction from resuming.

In other words if there is no free Cl but excess nitric would the reaction resume after adding more hcl?

Yes and yes.

You tend to see your solution dropping everything out when you run out of HCl. It goes really cloudy- is that what you saw?

Also adding extra HCl instantly clears it up and doesn't involve a massive rush of reaction.
 
Yes it cleared up a bit but still the green precipitate was there with some bubbling but no NO2 fumes.

Ok thanks
 
I totally agree with Jon, some of the gold is probably mixed in with the yellow precipitate. I could have expressed me more clearly in my last post.

I did some more diggin and I'm pretty sure that the yellow precipitate is insoluble tungstic acid.
https://en.wikipedia.org/wiki/Tungstic_acid

Göran
 
Williamjf77 said:
Thanks goran, actually after I took the pics I took some gold powder I had and made a standard to test the stannous.

Turns out my old stannous was still good but both bottles actually either blew off the dropper bulb or eroded it, I’m not sure, it is pretty cold here in New England, maybe that had something to do with it or maybe the cheapo glass dropper bottles.

Tomorrow I will try fresh AR on the chips and the precipitate separately and I’ll update the results.

I got tired of rotting the caps off of dropper bottles and picked up a small bottle of eye drops. I emptied the bottle and removed the label which I replaced with permanent marker label. I really like these and still keep them on hand. (be sure they are kept put away where they won't be mistaken for the eye drops) I now have a couple of bottles that are glass that are large scale droppers but I never need that much stannous so I still use the small plastic ones. Keep the lid loose as they will build pressure over time.
 
FrugalRefiner said:
I use these a lot. Currently $5.49 for 50 10ml bottles.

Dave

Actually I just received a order of those today,

One interesting thing that happened with the glass bottle and dropper Is when I made the fresh solution of stannous I left it in my garage with everything else outside the fume hood, it is unheated and the bottle was empty with the dropper bulb sucked in , I can’t tell where it went but just in case someone else reads this I don’t think the cheap glass Boston round dropper bottles are safe if kept in the cold.
 
You don't need too big a temperature difference to suck the bulb in, gas changes volume quite a lot when coming from hot to cold.

Göran
 
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