# Aqua Regia



## ozyredeye (Aug 26, 2011)

Hi All

1st Post and totally green to the Gold recovery process

Without sparking a war here , could some one tell me what the correct procedure is in making and recovering gold with Aqua Regia 
I hope this was the correct section to post this 

Cheers Marty


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## jimdoc (Aug 26, 2011)

ozyredeye said:


> Hi All
> 1st Post and totally green to the Gold recovery process
> Without sparking a war here , could some one tell me what the correct procedure is in making and recovering gold with Aqua Regia
> I hope this was the correct section to post this
> Cheers Marty



Marty,
You should do some reading here on the forum, as well as Hoke's book (available for download).
Look for forum member Palladium's signature line for a link to both of her books, they have the answer to your question as well as the answers to some of your future questions.
Aqua regia isn't the best choice for much electronic scrap. I don't know what you plan on refining, but I suggest you take it slow and read all the safety aspects, as well as some of the alternative ways to do computer scrap.

Jim


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## Geo (Aug 26, 2011)

absolutely. you should have a rudimentary understanding of the chemicals used at least before you try any process in this forum or anywhere else as far as that goes. the miners of yesteryear called the red fumes(nitrogen dioxide) from the reaction of nitric acid on metals as "the red death". even short term exposure to this can kill you days after inhalation from pulmonary edema (swelling in the lungs). it kills living cells on contact. it also happens to be one of the ingredients for Aqua Regia. happy refining. :lol: please be safe.


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## ozyredeye (Mar 8, 2012)

Hi Again 

I had lost the forum page Doh

I have read though some of the book in regards to the recovery process , the pins I have are 14k what the book didnt tell me is how much sodium metabisulfite to use, ones the gold has been dissolved and that there is a formula to test your solution, I have not been able to find this

Form I have read by adding the SMB this will drop the gold from the solution 

I have worked with Hydrofluoric Acid and Methoxide and em aware of just how dangerous some of these acid can be , and that safety is paramount and AR would be no different , 

Is there a step by step how to at this forum ?

Cheers Marty


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## Geo (Mar 8, 2012)

Hoke's book IS the step by step. there is a reactions list in the guided tour. spend some time reading and then ask specific questions about what you are working on, asking a generalized question will get you a generalized answer.


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## ozyredeye (Mar 9, 2012)

Mate what page is this reactions list as I didnt see one

Cheers Marty


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## Geo (Mar 9, 2012)

http://goldrefiningforum.com/phpBB3/viewtopic.php?t=562

here you go.


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## Harold_V (Mar 10, 2012)

ozyredeye said:


> I have read though some of the book in regards to the recovery process


Some of the books? 
You have been admonished to read *Hoke's book*. Have you?

Do not take this lightly. If you do not understand what Hoke teaches, you won't get far on this forum. Reading her book will put you on a common footing with the readers, in spite of the fact that she does not discuss the refining of escrap. The point is, she discusses refining. When you understand her teachings, you can then interpolate her information such that it applies to other materials. 



> the pins I have are 14k


You have 14K pins? 
Can you please disclose the source of these pins? How were they used?

Harold


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## Nickpearl (Apr 10, 2012)

Good day, Harold, et. el.
Just a bit of confusion.

The Gold Refining Forum Handbook Vol 1 has the Aqua Regia formula per Hoke as follows:

"Hoke states 4 fluid ounces HCl + 1 fluid ounce HNO3 dissolves 1 troy ouncegold. This is equivalent to 31 mL HCl + 8 mL HNO3 per gram of gold."

Lazersteve (I think correctly) converted this to a "per gram" amount ...."Hoke states 4 fluid ounces HCl + 1 fluid ounce HNO3 dissolves 1 troy ounce gold. This is equivalent to 3.8 mL HCl + .95 mL HNO3 per gram of gold"

This matches dividing Hoke's formula by 31.1 grams (after converting ounces to 29.574 ml).

Correct?

Thanks, all.
Nick


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## Geo (Apr 10, 2012)

Nick, its a widely accepted procedure on the forum to NOT premix AR solution. you can if you feel more comfortable doing it that way but the the more accurate and less wasteful process is to add the amount of hcl needed for the reaction (plus a small volume extra as its better to err on the + side of hcl) and add the nitric acid in small increments until the reaction is complete. in most cases this will require less nitric than is recommended in premixing the solution (thus saving chemicals and reducing waste) and eliminates the need to rid the solution of free nitric at the end of the process.


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## Nickpearl (Apr 10, 2012)

Thank you, Geo.
I will proceed from now on in that manner. I have, however, used BDG lately (no need to cook off the HN03) but for some reason I didn't capture all the AU (I think). Still, if I can proceed by adding the HCL, then slowly adding HN03 until (I assume) it stops bubbling, I will be successful.
Thanks, again.
Nick


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## Geo (Apr 10, 2012)

the reaction is more efficient and faster if you heat the solution during the process. keep it below the boiling point. remember to cover your reaction as the tiny bubbles bursting at the surface creates a kind of aerosol spray from the solution itself and leads to loose of values.the reaction is complete when all metal is dissolved.


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## goldsilverpro (Apr 10, 2012)

Nickpearl,

I've never used BDG and probably never will. I could be wrong, but I was under the impression that the nitric had to be removed first. If I'm right, maybe that's why you're not getting all the gold.


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## samuel-a (Apr 10, 2012)

Free nitric degrade the organics, but does not hinder the stripping.
Test left over solution with SnCl, if needed, run a second time with BDG.


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## Nickpearl (Jan 26, 2013)

Hello all and it's been a while;
To awaken this thread from last March, my routine has evolved to thus:
1. After obtaining material ready for AR through either removal of gold from china and glass, or from gold filled, heavy gold plate (think military contacts) through Nitric and rinse, I then AR the batches.
2. I confess (on my knees weeping) that I still pre-mix the AR.
3. It cooks, under heat, for approx. four hours. In the latter stages I dilute and let steam.
4. I do use the Butyl Diglyme to drop the gold per LazerSteve procedure.
4a. After dropping, I save the used AR and when I've collected a quart or two, I use SMB to drop. I always get some precipitate, uncaptured Au plus PGM? I'm saving the filters until I know what to do with them.
5. Rinse with hot HCL (mixed with some hot water), rinse with water, dry, melt and produce the buttons.
6. I reclaim any silver in the waste using copper. I then raise Ph to 2.5 and drop copper using cast iron. I then raise Ph to 5-6 and the iron drops.
7. left now with a Ph neutral liquid slightly green, I gently heat and add ammonia and a yellow-green misty substance precipitates. I filter this out (What is it?) Is it Nickel? PGMs? In any event, my waste liquid is clear with the Ph of water and I dispose.

These buttons now, having done this for over a year are so much cleaner than when I first started. I have multiple two inch jars separated into two classes - from glass and from metals. With metals, I measure what I start with (contacts I just weigh after torched into flakes - the gold fill is noted), and record the results. I maintain a close yield to what I start with on the gold fill. 100g of 1/20 12K should yield 2.5g gold. I routinely get 80-90% of that amount, sometimes worse (waste, wear and tear of the fill, hopefully not wasting anything through the chemical process or dropping process).

My next step is to either assay the gold and/or send some to a refiner to establish my selling process. I will explore two places locally here in Minneapolis, but I've heard good things about a refiner in Texas.

So what's my point? 
1. I will commit to start adding the nitric slowly instead of pre-mixing the AR. Since you all are practicing this, I should be current.
2. I will find what it takes to test for PGM. I'm sure all those re-SMB dropped filters from previous AR batches contain PGM as the DMG selects for AU only.
3. What is this yellow-green misty precipitate I described above? ("left now with a Ph neutral liquid slightly green, I gently heat and add ammonia and a yellow-green misty substance precipitates. I filter this out (What is it?), my liquid is clear, and I dispose."


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## nickvc (Jan 26, 2013)

Nick point two..
Stannous chloride will prove if your solutions contain PGMs not only gold.
Point three..
There will be no PGMs after you dropped the copper from your solutions, if you cement your solutions, after precipitating your gold, with copper the PGMs should be there.
Hope that helps.

Edited for clarity.


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