Refining Golden Foils From Fingers (Aqua Regia)

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Tzoax

Tzoax

Well-known member
Joined
Apr 10, 2014
Messages
423
Location
Serbia, Belgrade
Greetings. I collected 5.3 grams of golden foils from mixed fingers (fingers from RAM, PCI cards, graphic cards and slot processors). I am going to process it with aqua regia. First I measured weight of golden foils (picture 1 and 2) and I put it carefully in a dish. I will post exactly what I am doing and we will see the results at the end. Any comment is welcome.1.jpg2.jpg3.jpg
 
Thank You very much Pantherlikher! I will post exactly what I do, with pictures and measures. Right now I am preparing and cleaning the dishes I will use.
The basic idea is to fill the golden foils with HCl (I will post exactly how much), then I will heat it (not to boiling point) and then I will keep adding a small amount of nitric acid, and observe the process until all golden foils are dissolved.
 
I added 200ml of concentrated HCl to the dish, slightly heated, and I keep pouring concentrated HNO3 in small amounts. I am observing the reaction and i will stop adding nitric acid when all gold foils dissolves, I will post later how much nitric I added.4.jpg
 
I believe you want to just cover the foils with HCL and then add your nitric in small increments until foils dissolve. Your going to have alot of excess acid to denox with that much HCl. If you havent added nitric I would let HCl cool and decant some of the HCL before you add your Nitric.
 
You could have also just used hcl/cl to dissolve the foils and then dropped with your precipitant of choice. If the foils were cleaned properly you should save your nitric for use on other harder to refine material. Just my opinion. Keep us updated please.
 
Thank You for replies, I found this text in Gold Refining Forum Handbook, so I thought it is right:

"AR= Aqua Regia = 1 part 70% Nitric Acid, 3 parts Muriatic Acid (some guys use 4parts muriatic). Used to dissolve high karat gold, gold powder, gold foils, dissolvesPlatinum when hot. Excess nitric must be neutralized with Urea to pH 1 +/- 0.4, thendrop gold with SMB.
o
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."

I made a mistake but i will keep that in mind for now on, thank You. What is the best proportion for HCl per gram of gold?
I used total 14.3ml of nitric acid and 200ml of HCl.
So, the gold dissolved (picture 1) and I added a small amounts of urea to neutralize nitric acid (picture 2), reaction stopped (picture 3), and right now I am filtering the solution, I will keep You updated.5.jpg6.jpg7.jpg
 
Tzoax said:
Thank You for replies, I found this text in Gold Refining Forum Handbook, so I thought it is right:

"AR= Aqua Regia = 1 part 70% Nitric Acid, 3 parts Muriatic Acid (some guys use 4parts muriatic). Used to dissolve high karat gold, gold powder, gold foils, dissolvesPlatinum when hot. Excess nitric must be neutralized with Urea to pH 1 +/- 0.4, thendrop gold with SMB.
o
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."

I made a mistake but i will keep that in mind for now on, thank You. What is the best proportion for HCl per gram of gold?
I used total 14.3ml of nitric acid and 200ml of HCl.
So, the gold dissolved (picture 1) and I added a small amounts of urea to neutralize nitric acid (picture 2), reaction stopped (picture 3), and right now I am filtering the solution, I will keep You updated.
Click to expand...
The proportions of HCl and HNO3 you quoted from the Forum Handbook and Hoke are correct - somewhere in the 3:1 to 4:1 range. It's the quantity of each that is excessive. The math in the underlined portion is incorrect. 4 ounces of HCl is about 120 ml, and one ounce of HNO3 is about 30 ml. That is correct for an ounce of gold. But the underlined portion represents about 1/4 the amount of acids for about 1/30 the amount of gold. It only takes about 3.8 ml HCl and 0.95 ml HNO3 to dissolve a gram of gold. You probably could have used about 25 ml of HCl and somewhere around 5 ml of HNO3. A little excess of HCl does no harm, but you'll have a lot of excess HNO3.

By the looks of your final solution, there was still a fair amount of base metal present (copper and/or nickel). Both require more nitric than gold, but you still overshot by quite a bit.

Just as Hoke's book contains some bits of advice that are outdated, the suggestion in the Forum Handbook to use urea to neutralize excess nitric is also outdated. There are better methods, e.g., adding more gold or using sulfamic acid.

Keep studying. There is so much to learn.

Dave
 
Thank You Dave. This is my first time refining gold from foils.
Filtered solution with gold is on the image 1.
I added SMB solution (19.5 grams of SMB and 34.2 ml of destilled water) little by little, there is a brown dust forming at the bottom of a glass container.
The reason I used that much SMB is that I waited that color of a solution becomes black/brown/white, but it is not.
On picture 2 is solution after adding 19.5 grams of SMB. I didnt made a stannous chloride, and I can't test it, does anybody know why the solution remains in this color?

I am guessing because of a little copper or nickel, but I am not sure, also does anybody know is this amount of SMB enough for this solution?8.jpg9.jpg
 
In general, you need about 1 gram of SMB for each gram of dissolved gold. In your case, you needed more because there was still excess nitric in your solution. Because you used much more acid than needed, the gold in your solution was quite dilute. That, along with the excess nitric, were the reasons you didn't see the classic "yoohoo" brown as the gold was reduced.

You must make some stannous. Without it, you are working blind. No one can really tell you if the amount of SMB was enough (though it probably was). Just save the solution until you can make some stannous and test it then. Base metals in a dilute solution could result in the color you see.

Dave
 
Looks good but you are using way too much SMB, you dont want to precipitate contaminants to your gold, this takes time to master but it is better to add in small ammounts until no reaction is seen than the excess... keep up learning and you will master it!!
 
I agree with Dave , you used too much SMB. It also looks like you didnt let it off gas long enough before you added SMB.
 
I added a huge amount of HCl and nitric at first place, for nitric I know for sure because I needed a LOT of urea to neutralize it. Then, when I saw that solution have still yellow color I was keep adding SMB until I reached 19.5, that is also a huge amount of SMB. I was unable to make stannous chloride because I was in hurry to get to my job, tomorrow I will make a stannous chloride, I will decant the liquid and test it, i will post the results. Thank You all for advices, You are all great.
 
Why people still continue to use urea? It is like introducing contaminants to your values in order to save time ypu lose value instead..
Patience is a key in this game. You should clean your foils more before AR. If you noticed your AR was deep green color that mean there was still a lot of base metals on your foils. Therefore you cant really expect your solution after smb to become clear.
I have never used urea and I do not intend to. All I do is to add nitric in drops, few drops at a time. It take a lot of time to get practice in doing this but that is what everyone should do. Do not process if you do not have time, try not to leave reactions unattended.

Take all what you filtered, all your solutions combine all that and warm it little bit to evaporate excess of water you introduced. Do not boil, just warm it so it will steam all that water off. Then put in some copper, bus bar or some sheet copper. Let solution saturate with copper and collect all powders from bottom. Incinerate them and start again.
 
very common in the beginning to use WAY too much nitric for base metal leach and AR. i found out quickly i was not just wasting money on nitric but making life a lot harder on myself by using too much acid for the job. sulfamic is a much better option for fixing a AR solution with a little too much nitric.

for me, when i get to the point of adding SMB, the solution immediatly turns dark and the gold drops fast. i have a small plastic spoon i use to stir and i always get a gold plating on the spoon in the 2 seconds after adding SMB and two quick stirs. i just use the same spoon next time to recover it back.
 
patnor1011 said:
Why people still continue to use urea? It is like introducing contaminants to your values in order to save time ypu lose value instead..
Patience is a key in this game. You should clean your foils more before AR. If you noticed your AR was deep green color that mean there was still a lot of base metals on your foils. Therefore you cant really expect your solution after smb to become clear.
I have never used urea and I do not intend to. All I do is to add nitric in drops, few drops at a time. It take a lot of time to get practice in doing this but that is what everyone should do. Do not process if you do not have time, try not to leave reactions unattended.

Take all what you filtered, all your solutions combine all that and warm it little bit to evaporate excess of water you introduced. Do not boil, just warm it so it will steam all that water off. Then put in some copper, bus bar or some sheet copper. Let solution saturate with copper and collect all powders from bottom. Incinerate them and start again.
Click to expand...

Thank You Patnor, great advices. I know couple of refiners, and they are all using urea, I asked one of them why he is not using method with adding slowly nitric or adding a gold button until nitric is neutralized and he answered me that urea is cheap and it does the job. I thought that it isn't much important.
Some of the foils I did with HCl/H2O2 and some with HNO3, I was learning and experimenting to see which method is best for fingers, I was still learning, and when I tested foils with magnet I found out there was still some of the nickel there. I decided to treat it with aqua regia because there are HCl and HNO3 together in foils, I thought it would be simpler that way and with no loses because I thought there are so little of nickel, then to incinerate and process it with nitric again. I am still learning, and this is my second time in life dealing with aqua regia, so the next time idothis will be much better.

I will decant solution, and test it with stannous chloride, if the result is positive I will try to add little more of smb and if there is no reaction I will do exactly like You said, I will start over, thank You again.
 
No need to add smb, mainly when you already added too much of it. Skip smb go for evaporating and then cement values on copper. Cemented powder should be dried and incinerated. Then you may want to leach base metals out of it with warm HCl maybe with few drops of peroxide. Then cemented powders (what will be left of them) can be redissolved in AR. Forget about smb till you do all of this.
 

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