# Aqua Regia refining.



## Aristo (Sep 27, 2007)

I am trying to reduce the intensity and flow of NOX gas from an aqua regia process. 
If I were to immerse say...40Lbs of fingers or cpu in hydrochloric acid and then add small amounts of nitric up to the desired amount.....would this compromise the gold recovery?. Would I end up with gold "locked" in solution?. I believe the addition of measured amounts of nitric would reduce the flow of NOX , however , I dont want to lose any gold in the process.
Thanks for all the replies.


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## Harold_V (Sep 28, 2007)

I am at a complete loss why you'd process them with AR when you could eliminate the base metals with nitric, then dissolve only the gold. You'd end up with a much cleaner product. While I haven't done the math, I can't imagine you save any acid by going straight to AR. What's the benefit? I must be missing something. 

Harold


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## Aristo (Sep 28, 2007)

Thanks Harold.
However , my question is still unanswered.


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## lazersteve (Sep 28, 2007)

Aristo,

Harold has a good point. You are actually using more AR than required by dissolving the whole lot as is. By removing the base metals first you can increase the economy of your AR and decrease your NOx fumes.

As an example of why adding the HNO3 in small doses does not change the NOx losses look at this thread about the amount of HNO3 needed to dissolve a single pound of plain copper metal. 

Nitric Equation

Pay close attention to the equation GSP uses, the point is that there is always a lose of NOx when you add HNO3 to base metals, the equation requires that a portion of the HNO3 goes up in smoke. You may be able to use more water to contain the NOx emissions, but the metal will still require the same amount of HNO3 be added to complete the reaction and hence the same NOx losses.

If you added another ingredient into the mix you may be able to convert the NO fumes to NO2 which then could produce more HNO3 with additional water if everything worked out just right. There is a patent posted concerning this subject here:

NOx Patent

Steve


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## scavenger (Sep 28, 2007)

Harold is correct on this topic. The problem with AR on complete cpus is that a cpu contains a lot more copper than it does gold. Any surface gold that dissolves will be precipitated again by the dissolving copper and u end up with a big mess. 
AR on fingers is even worse. I've had fingers distort and crumble from the heat of the reaction. 
I only use AR for solid gold and crushed cpus that have been completely stripped of all base metals.


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## Redders (Sep 28, 2007)

I have taken the plated lid off some cpus and I am left with the legs and the exposed proc which obviously has some gold in there. How would you finish these cpus.

You crush the body, legs and all? you incinerate? how big are the pieces? then you use AR? Are there wires to each leg that can be recovered? 

I have a good boxful of cpus and I am deciding on a strategy... (you nth or sth island?)


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## Aristo (Sep 28, 2007)

I certainly do agree with Harold's perspective , however , isnt it true that the disposition of non Au metals will cause the same emissions with HNO3 as with AR?.

I will study the link posted by Steve...thanks Steve.


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## goldsilverpro (Sep 29, 2007)

Aristo,



> I certainly do agree with Harold's perspective , however , isnt it true that the disposition of non Au metals will cause the same emissions with HNO3 as with AR?.



Yes. All in all, when using nitric alone or in any acid combination, about half is lost in brown fumes. This varies a bit as to temp., concentration, etc. I do agree with Harold, however. You are better off to either first dissolve the gold or the base metals - not both at the same time. In this case, nitric is precious - why waste it. Use Steve's method of dissolving the base metals first, without nitric.

On the original question:

It's all equal. With small adds of nitric, you're just releasing the fumes at a slower rate. The total is the same. It's based on the total metal dissolved. 

In 40 years, I have never ever seen gold "locked" in acid solutions, under any conditions. If it's dissolved, it will always drop out, using the common precipitants. Just make sure the solution is filtered clean before doing it.


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## Noxx (Sep 29, 2007)

And I just want to add,
If you use Hydrogen Peroxide with your nitric acid, you won't have any fumes and you make it better.
That's it...


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## goldsilverpro (Sep 29, 2007)

Have you tried the peroxide with the nitric or aqua regia, Noxx? How well does it work?


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## Noxx (Sep 29, 2007)

No I haven't yet because concentrate Hydrogen Peroxide is expensive... And the winter is coming soon... No more refining for a few months lol.


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## scavenger (Oct 2, 2007)

Redders said:


> I have taken the plated lid off some cpus and I am left with the legs and the exposed proc which obviously has some gold in there. How would you finish these cpus.
> 
> You crush the body, legs and all? you incinerate? how big are the pieces? then you use AR? Are there wires to each leg that can be recovered?
> 
> I have a good boxful of cpus and I am deciding on a strategy... (you nth or sth island?)


Hi Redders, I'm Nth Island mate. Lived in Sydney 4 years. Great place.
Regarding the cpus, first clean off any grease and dust etc...
Leave them whole in HCL/Peroxide or dilute nitric (10-20%) for at least a week. Do not agitate because the plating will break up into smaller pieces 
making it harder to deal with.
Gently pour off as much acid as u can without disturbing the settled gold.
Pour in enough water to cover the cpus and begin removing each one washing off any clinging gold plate in the water as u do.
U will find that the cpu is completely stripped of all outside metal.
After they have been removed let settle for a time and carefully pour off the remaining liquid. U should be able to pour off the lot without losing any fine gold particles.
U will have complete hollowed legs, plating and proc chips left in your bucket.
U can filter the chips out after u have dissolved the gold or remove them one by one if u have the time.
There is gold left in the cpu but not much and its a lot of work to get it.
Best to wait until u have a decent amount (300+) before u bother.
Hope this helps u out. Cheers Dave.


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## Redders (Oct 3, 2007)

How would you deal with these? There doesn't look to be much value in them. I guess AcidPeroxide the cpu whole. That will get the legs...... is there anything in the chip? 

I must go for a drive around The Shaky Isles again. (I've had my head up my arse working for too many years)


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