# Gold won't drop! HELP! Please!



## Shawn618 (Nov 13, 2013)

Hey guys, 

This is my first post so excuse any mistakes thanks.

So I had 500grams of intel pentium pro processors so about 10 chips,
I usually dealt with p1 ceramic CPUs I recovered about 2.5grams of gold
from 1kg of those and did that about 3 times successfully.

But with this I messed up somewhere... Here's exactly what I did. 

I headed the chips and took the bottom lid off. I didn't break any of the chips 
I soaked that in 500ml of HCL 36% and added about 100ml of water.

Than I headed the solution in a bath of boiling water with continues heat.
Than added NaNo3 (sodium nitrate) one teaspoon every 10 minutes. ( I usually decrease the sodium
Nitrate by 1/2 every time I add it but this has more gold than I'm usto so I did 2 full spoons than 2 halfs) heated it for about an hour than I let it cool to room temperature fitiltered the solution than added about 7 ice cubes and 50 ml of sulfuric acid by drop than let it sit for an hour and half than I filtered the silver and lead that precipitated now I had this solution that had gold left in it so I added 2 teaspoons of UREA to neutralize the nitric acid.. Than added a teaspoon of SMB it fizzed a bit and a little red between the fizz but only if I add alot to one spot but it did fizz.. So I let it sit the night... And nothing in the morning it looked exactly the same.. I checked it with Stanous chloride ( I check it by mixing the tin2chloride power with water and putting a drop of the mixture on a tissue and than added a drop of the solution) the tissue darkened a bit.. But I think that's because there is alot of the solution... So I read a few forms and read that a sodium hydroxide solution dropped in will help the gold drop.. So I tried it and every drop that went I. The solution turned completely black and floated on top I added about 100ml of that the form said 50ml but I had 500ml of hcl to begin with So I thought it would be right to double the amount.. 

But when I stir the soulition it just dissolves.. Please help and thank you in advance to who ever took the time to read this... 

Shawn Memon


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## Pantherlikher (Nov 13, 2013)

Hi Shawn
So...let me get this right. You have done 3 successful gold drops from P1s using this method you described completely?
"I usually dealt with p1 ceramic CPUs I recovered about 2.5grams of gold
from 1kg of those and did that about 3 times successfully." Is this the yield for 1kg?

How did you dispose of the spent solution when you did what to it?

Trying to follow the steps you took, it was difficult to visualize how you got anything but Lead out of "poor man's nitric" acid. Gold does not dissolve in nitric acid alone. Does sodium nitrate and warm water create an acidic solution? What's the purpose of boiling things in water bath?

"Than I headed the solution in a bath of boiling water with continues heat."
What does "headed" mean?

Reading it 3 times now, I'm assuming you split the chips in half, soaked in HCL and added sodium nitrate? Confusing part. 
Hopefully, you soaked in HCL, drained. Added HCL and then added sodium nitrate + water. This would make AR which would dissolve most things. Silver would be a problem if present. Is silver present in any ceramic processor?

You need to read "THIS" forum for quite some time to see how we use urea. 

You dissolved tin2chloride power with water to test. Does this create an acidic solution? tin2chloride power with HCL would. But you could get that when mixed with the solution as it has HCL in it. Just seems not right as you are dilluting the testing solution.

"So I read a few forms and read that a sodium hydroxide solution dropped in will help the gold drop."
What other forums did you read this from and what reaction is it supposed to do?

My suggetion since you just joined "THIS" forum, is to read the welcome post. Followed by rules and then safety section. These are extremely important to us.
If you follow the steps I suggest, you will find your answers as you follow along the path which will guide you to the complete understanding of what you are doing and what is happening and why.

Hopefully you saved everything you did. material and solutions. You have gold there but you might have it hiding from you. Or the precipitation you have is far from pure. 

This is about the best "help" any of us can give you. You need to better understand the process from start to finish including what exactly happens when you mix 1 thing with another. Hopefully in a safe manner as to not cause anyone harm.

B.S.
...Welcome to the forum and hopefully we get to see pictures of your prize...


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## butcher (Nov 13, 2013)

Shawn, 
I started to type a reply yesterday, but I was so confused about what you were doing, I decided to delete it.

Sounds like you have done some homework, but learned this from all the wrong places, I think you have a lot of re-learning to do.

Download Hokes book to study, and study the forum.
Take the forums guided tour (in the general chat section).
Read dealing with waste and the other topics in our safety section.

Welcome to the forum, with some serious study you will improve your skills, and with study there will be very few questions that come up, that you will not be able to figure out, with the education you gain, and you will actually learn the basic principles of recovery and refining of precious metals,its chemical behaviors, and understand how to deal with most any situation, learning also what works and what will not work and why.

Putting away the acids, and getting out the books will be your best bet of getting pure gold in your melting dishes.


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## Shawn618 (Nov 14, 2013)

Hey guys thanks for the reply,

And headed was supposto be heated.. Sorry I actually work 11 hour shifts everyday so I reply from my iPhone 
Really sorry about that 

Now I had this poor mans ar i suppose the the things mixed in my soulition I have which I will not dispose of untill the gold
Is dropped, 

So I had HCL 500ml + 100ml water,
Than I heated it to 160 degrees c 
Added the sodium nitrate.. 
Than added the ice and sulfuric acid after 
it was cooled to room temperature.
Than added urea and after than SMB..

Again sorry for the confusion. Thanks for all your help
I will gladly read the hoke guide and the welcome thread


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## butcher (Nov 14, 2013)

With poor mans aqua regia, you are adding a nitrate salt which with hydrogen from an acid can convert to nitric acid in solution, here you were using HCl for the acid, the nitric in solution, along with the gases produce in the reaction will oxidize gold, the free chloride ions will combine with the gold to form a solution of gold chloride AuCl3, with base metals in solution they are also oxidized and can form chlorides in solution, (some like tin may not go into solution but oxidize to a gelatinous goo in nitric, or a stannous chloride in acid chloride solution, both of which would cause problems).

With poor mans aqua regia the amount of nitrate salt added is critical, if you add too much you can end up with a situation where you are leaving dissolved nitrate salts in solution, Which can easily convert back to nitric acid if free acid is involved, also base metals in solution can make salts of nitrates like copper nitrate.

Urea does not destroy nitric acid, it will not destroy nitrates either, (Urea will react with NOx gas in a pure concentrated nitric acid solution and destroy the NOx gas involved, but it will not destroy the nitric acid), urea also can be dangerous to use, forming ammonium nitrates, and if the platinum group metals were involved can complicate the recovery or chemistry of these metals.

Because of the possible dangers, and complications involved with the use of urea, the fact that it will not destroy nitric acid, and so on, the use of urea is not advised, there are much better ways to deal with free nitric acid in aqua regia.

With poor mans, you may or may not have free nitric acid to de-NOx, you may or may not have nitrates left in solution, which can complicate the nitric, NOx, or nitrate removal, before your gold will precipitate with an chemical reagent in the acidic conditions, much depends on how much acid, nitrate salt, the metals involved, and the conditions you were working under, you do not want nitrates, nitric, or NOx gases in solution when trying to precipitate gold from solution, you definitely do not want tin from solder in solution, and ideally you do not want base metal in solution with gold.

In Hokes you will learn How to de-NOx aqua regia, but she was not working with poor mans, where if you have too much nitrate salt (where you can create problems), and do not convert all of the fertilizer (NaNO3 or KNO3) to nitric solution in the poor mans, and then react all of the nitric acid formed in solution with metals, to consume all of the nitric formed in solution where you will be left with basically just a chloride solution (maybe only a tiny amount of free nitric or NOx) that could easily be removed by concentration through evaporation and keeping the concentrate acidic.

Where there are nitrate salts in solution when you evaporate a solution you can concentrate or even crystallize out base metal salts like copper nitrate, so basically when you dilute you can be just redissolving these back again into solution, leaving you with a solution with nitrates in solution much like you had before the evaporation process (here the amount of nitrate used to make poor mans is critical to success). 

By adding a Hydroxide to the solution you just made a mess into a bigger more complicated mess.


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## niteliteone (Nov 14, 2013)

Sounds like it's time to drop a copper bar into the mix for a week or so, to drop all the values while consuming the excess acids. 
While you are waiting for this to happen, it would be a great time to "read and learn" how to deal with what cements out of that mess.


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## butcher (Nov 14, 2013)

I cannot remember if I calculated this before, but thought I would try it again.

How much poor mans aqua regia to dissolve gold:

First we need to make nitric in solution (to oxidize gold), note here we are using a 32% acid solution to get the hydrogen needed, this will make a very weak acid nitric acid for aqua regia (around 30%), if we do not add water, additions of water dilute this further, and since our acid source is HCl we will also have salt of NaCl as a byproduct, for the formula we will use a mole of sodium nitrate mixed with a mole of hydrochloric acid to get a mole of nitric acid dissolved in a salt water solution:

NaNO3 + HCl --> HNO3 + NaCl

Now we already used a mole of HCl but we still do not have enough to make aqua regia (poormans).

Formula for Aqua regia:
HNO3 + 4HCl --> NOCl + 3Cl + 2H2O
aqua regia with gold:
Au + HNO3 + 4HCl --> HAuCl4 + NO + 2H2O

so we see, we need 5 moles HCl in poormans aqua regia, one mole to generate HNO3, and 4 moles for the aqua regia to dissolve gold.

So our poormans formula with gold would look something like this:
One mole of gold plus one mole of sodium nitrate plus 5 moles of hydrochloric acid, to make an acidic solution of gold chloride:
Au + NaNO3 + 5HCl --> HAuCl4 + NaCl + NO + 2H2O

Lets continue plugging in facts and numbers:
HCl acid is HCl (g) gas dissolve in water
One mole HCl(g) is 36.4g/mole (remember this mole of gas is dissolved in water).
32% HCl is about 10.2 Molar per liter
So 1000ml/10.2M =98ml of 32% HCl contains 1 mole HCl
Density of 32% HCl 1.16g/ml
So 98ml x 1.16g/ml = 113g HCl (one mole HCl 98ml 0f 32% HCl acid).

From our formula above we need 5 moles HCl (with one mole NaNO3 to dissolve one mole of gold):
5 x 98ml (32% HCl/mol) = 490ml (32% HCl needed to dissolve a mole of gold)
Or
5 x 113.7g HCl = 565g HCl

We also need a mole of NaNO3:
From the periodic table sodium has a molecular weight of 23, nitrogen 14, oxygen 16 (we have three oxygen so we have 3x16 or 48)
adding these together we see one mole of sodium nitrate is 85g/mol:
NaNO3 85g/mol 

And from the periodic chart we see one mole of gold is 196.9g/mol (I will use 197g/mol)
Gold Au 197g/mol

To get troy ounces of gold in our formula above:
197g Au / 31.103 = 6.33 troy ounces of gold


so here we see to dissolve 6.33 troy ounces of gold in our poor mans mix of 490ml HCl and 85 grams of NaNO3.

But we are not dissolving this much gold.

So to figure for one ounce of gold:
490ml HCl / 6.33 = 77.4ml 32% HCl (per troy ounce of gold)
85g NaNO3 / 6.33 = 13g NaNO3 (per troy ounce of gold)

How much to make poor-mans aqua regia for each gram of gold:
77.4ml HCl / 31.103g/tOz = 2.48ml of 32% HCl (to dissolve a gram of gold)
and 
13g / 31.103 = 0.4 grams of NaNO3 (to dissolve a gram of gold)


So we see for each gram of gold we have we need about 2.5ml of HCl acid and I would not use over a half gram (0.5g NaNO3) of nitrate salt (adding it in small additions while heating the solution, and if the gold dissolved before I finished adding the nitrate I would not have to use all of that fertilizer).


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## Pantherlikher (Nov 15, 2013)

So.....
As you see by the posts following my first. It is extremely important to learn what you are doing so you do it right and not make it alot more complicated or dangerous then it should be.

This is why reading and learning how it works is so important.

Again...
Good luck and show us the results of your study.

B.S.


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## Bitcollector (Feb 21, 2021)

butcher said:


> I cannot remember if I calculated this before, but thought I would try it again.
> 
> How much poor mans aqua regia to dissolve gold:
> 
> ...



I'm new here, so I don't understand some things as I'm reading. 

One thing puzzles me when I read the recipe for refining gold, I see, use so much HCl and use so much Sodium nitrate, or whatever, for 1 g of gold refining.

How do we KNOW how much gold we are going to get? Or does this term mean 1 g of metals before refining?


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## butcher (Feb 22, 2021)

Say you have a ring, weigh it, looking for stampings, test it for karat (verifying the marked karat), so you have say 10 grams of a 14 karat gold ring, or 14 parts of 24 parts of gold, dividing 14 by 24 and we get the value of 0.583 parts gold, or around 58% gold, so then our 10 grams of the alloyed gold ring X 0.583(parts of it being gold) = around 5.83 grams of gold. 
After parting the gold (recovering the gold) from the silver or other base metals you should have somewhere around this weight in gold.

Note: 14 karat gold can actually be 13.5K so your mileage may vary somewhat.

If you have placer gold you can figure 80 to 90% gold.

If you recover gold from electronics you can weigh the recovered gold flakes or gold powder.

As you can understand other metals if involved can consume reagents, other factors size or bulk, fine powders can dissolve fairly fast, while large chunks of metal will take more time and may need heat to speed reaction or consume more reagents due to loss in fumes or deadly gases escaping reactions.

Dilution can also affect the results, slowing reactions, and saving acids (slowing loss due to gas evolution), as well as heat these can be major factors in acid consumption...


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## nickvc (Feb 22, 2021)

As Richard has pointed out it’s not that simple unless you have a known or suspected gold content, and if you have base metals present as in karat scrap then the acids will be consumed much faster.
The only advice I can offer is to make sure you have plenty of HCl over your scrap and add oxidizer, take your pick here, in small increments as needed or basically as all reaction ceases add a little more, if no reaction occurs add a little more HCl and see if the reaction restarts.


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## Geo (Feb 22, 2021)

If you are working with electronics, No matter if it's clean foils or CPU's, it's best to add an excess of nitric acid or solid nitrate because there is no way to know how much gold is there. This means that destruction of excess nitric acid is necessary for every process. Urea is the old standard because it is used world wide as a fertilizer. A better choice is sulfamic acid. It is tricky to use and doesn't seem to destroy the free nitric acid every time. It is the process in which it's used that is to fault and not the chemical. It should be added to a hot solution in very small increments to start with ever increasing amounts as the reaction get less violent until you are adding it by a heaping spoon full at a time. When the reaction stops, that does not mean that the nitric acid is destroyed. It should be kept hot for at least an hour and allowed time to react. After an hour, test with a pinch of sulfamic acid to the hot solution. If it reacts, repeat the prior steps. If it doesn't react, it's safe to assume the excess has been destroyed. The solution, while containing excess nitric acid, will appear a light color regardless of contamination content. Once the excess nitric acid is successfully destroyed, the solution will appear darker. Much like you would expect post successful gold drop darker.


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## nickvc (Feb 23, 2021)

I do not like sulphamic too much especially if you have used way too much nitric, by converting to it to sulphuric you can have problems filtering your solution as the sulphuric will digest your filter papers but I can see why it is the recommended course of action, the best solution is the one that the late great GSP recommended which is what I outlined as that hopefully leaves only a small excess of nitric to convert.


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## g_axelsson (Feb 23, 2021)

If you have a lot of excess nitric, just evaporate the most part of the liquid. It takes a long time, but it works without any extra chemicals and next time you might have learned your lesson and not use too much nitric.

And for a good learning experience, just use evaporation and dilution with HCl a couple of times as described in Hoke.

Göran


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## Trinity358 (Mar 6, 2021)

Bro, I think you missed something check out this video on how to recover gold from the green fiber pin processor https://youtu.be/Xwoq7T3yE1A


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## Alabama938 (Mar 7, 2021)

@butcher

I just did that exact same math in my notebook two nights ago, then find it reading the forum. Really nicely written out, a mole of gold would be so pretty

My questions on poormans AR.

1 - because of the increase in reactivity associated with potassium, is that a better nitrate or at least usable? that’s all I have. I realize the molar mass will increase The amount required.

2 - is it better to make a concentrated solution of the nitrate as opposed to adding the coarse powder?

3 - is there a thread or a reference section for the amount of metals(not just Au) stored within different types of CPU? Or at least a ballpark amount?

Roll Tide

Also, I’ve been reading the Hoke book and The part where she says shut yourself in a tightly sealed room with no machinery and open a window and hope the fumes drift out is hilarious


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## butcher (Mar 8, 2021)

1 -I do not know how well I can answer this question, I prefer using the sodium salts over potassium for making poor man's nitric, or poor mans aqua regia, (that is if I am not distilling the nitric solution for purity), and just planning to freeze out some of the sulfate salts, I feel both salts can be used and have their advantages, sodium seems to have better yields and just seem easier to deal with.
When relying on freezing out the Potassium salts, the potassium salts seem to trap more of the nitric solution in the solution of the crystals with the insoluble salts, and it can more difficult to get a decent separation, and or decent yields without more troubles. Although if distilling or considering the waste byproducts, then I normally prefer making the nitric with potassium salts.

2 - I can see no reason to make a concentrated fuming nitric solution, a 68% nitric concentration is the most concentrated solution we need to work with, and often times half that concentration is often better when working with metals, if the solution is made weak, to begin with, the solution can be concentrated with the heat and evaporation of the water involved, many times this will also help your nitric acid go further as not as much of it is wasted in the making of the deadly red cloud of NOx gases as when the more concentrated solutions are used.

3 - I cannot say, you could try searching for the data sheets, and other information from the manufactures of the CPU you are interested in.


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## Alabama938 (Mar 8, 2021)

Thanks for the info… I’m going to try to use a scrubber with sodium carbonate to make sodium nitrate with my waste for my next run. 

I did make a 3M solution of potassium nitrate so I could use a pipette to add it without taking off the watch class

Finally ran my first PM AR on 300 g of chips and some other foils without BM from some other experiments with actual nitric which I really don’t like having around. I used an excess of HCl and half a mole of KNO3 in solution. It did not dissolve all of the metal by the time I had to go to bed, so I turned off the gentle heat and allowed it to cool overnight… This morning the stannous test is negative! which I’m assuming means any gold that was in solution cemented out on residual base metals not yet dissolved. So at work all day today I’m going to try to decide whether to decant and run it again with fresh acid or simply add more potassium nitrate, reheat, assuming that there’s still plenty of HCl around. I’m leaning towards fresh acid because 4Cl- is required for the chloroaurate ion

But man when it started getting that bright yellow golden solution color that I’ve seen on numerous videos and pictures but never in person it was extremely exciting. All this makes me remember how much I loved chemistry in high school and college.

I appreciate all you guys being so open with information and experience


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## butcher (Mar 8, 2021)

oxidation is a loss of electrons.
The reduction is a gain of electrons.

These are redox reactions if one thing is oxidized (such as gold) the other is reduced (such as our acids), for example, if we dissolve or oxidize gold with acids, during the process while the gold is being oxidized (losing electron), the chlorine gas is reduced (gain of the electron) in oxidization state to a chloride ion now with three chloride salt ions sharing the electron with the ionic gold salt.

In the stannous chloride test for gold, for the test to show a positive for gold in solution or to color it violet, the stannous chloride has to be able to reduce the gold ions (dissolved salt of gold) to elemental gold metal or clusters of these gold atoms.

Remember this is another redox reaction, note that during the process of gold reduction (gain of an electron) in the test for gold, here the stannous chloride SnCl2 itself must be oxidized (lose of an electron) which itself then forms stannic chloride SnCl4 ions in solution.

To reduce the gold (a gain of electrons), in the test, gold ions are reduced and form polarized clusters of gold atoms shoving each other around in solution so that they reflect violet light), and basically these clusters of elemental gold will never settle out of solution, free nitric acid in an aqua regia solution can prevent the gold reduction process in the test, or the free nitric can oxidize the newly forming gold clusters taking electrons their atoms, again leaving you with the gold ions dissolved in the chloride ionic soup, so the violet color may appear and then seen to soon disappear during the test.

Consider if there is much free nitric in solution the stannous chloride may not be able to reduce the gold ions in solution to a violet-colored colloidal cluster of polarized elemental metal atoms in solution.

Consider also, if the stannous chloride can reduce the gold ions, giving back electrons to form clusters of atoms that reflect the violet color in your test, free nitric acid in the solution can oxidize the clusters of gold atoms, taking electrons to form a dissolved salt of gold and chloride ions, where you may notice the violet color of colloidal gold disappearing soon after it forms.


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## Alabama938 (Mar 8, 2021)

If there is residual nitrate, it should be very low, But never actually gone. I added the last of my 1/2 mole of KNO3 and ran on heat for two hours and the reaction was quite mild when I turned things off. 

The test definitely did not turn purple and then clear again. Sounds like the smart answer is to keep going with the solution I have, in case I’m getting a false negative or an improperly observed negative (user error).

If I were to decant filter the liquid and continue running the batch with fresh reagents, should I go ahead and try to drop the gold from that filtrate, as opposed to adding the solution from the next run on the same material. I’m only asking because the 2 L beaker that I have, tall form, is a little over half full and making me nervous.


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## butcher (Mar 8, 2021)

Nitric and nitrate are basically two different animals of the same family here, nitrate is a salt of nitric, adding hydrogen from acid like HCl to the nitrate ion oxidizes it back into nitric acid.
(here the HCl is reduced to chloride ions).

There are many ways you can do it. you can always use a clean plastic 5-gallon bucket and a clean thick bar of copper...

Gold cement or reduced gold can be a fine powder making losses more noticeable when working with many small batches, and with a small loss in each batch, as opposed to working with one larger batch where one small loss would not be as noticeable.

You will want to eliminate nitric and nitrate salts from your gold, consider this:
You have the elemental gold powder in a pile, along with some insoluble nitrate salts, 
OK, good now, but what happens when you go to wash your gold powder to remove some base metals, and you add an acid such as HCl to the gold powders? Well, by adding the acid or hydrogen ions, you have made some aqua regia to redissolve the gold, basically defeating your purpose of washing the gold...


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## Alabama938 (Mar 8, 2021)

Small loss with each batch is a great point. I was going to try to avoid the copper bar technique, but it’s a nice to have a bailout. Are there any conditions that would improve the rate of cementation like heating, stir bar in the beaker, pH manipulation, or using silver.

I majored in chemistry and biochemistry, but have been in medical field for last 20 years, so forgive my excess of questions but this is all so fascinating. 

I was planning on denitrifying The solution with sulfamic acid. I’m thinking this is going to take longer then would normally be seen with nitric acid based AR.


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## butcher (Mar 8, 2021)

I would consider using a combination of Hoke's evaporation technique. along with Harold's trick of adding a gold button, and then sulfamic acid to insure nitrate and nitric removal.

The Hoke evaporation method will help to remove nitric as well as the nitrate salts (as you reacidify the solution before further evaporation) this also can be seen as the solution evolves the red NOx gas fume during the process. the gold button consumes free acids, and the sulfamic acid can help as well as help with removing lead as lead-sulfate from solution, the sulfamic which helps to form sulfuric in the solution can also help to convert nitrate salts to nitric acid and thus to NOx in the evaporation heating process as well. 

The batch that last dissolved the gold in the first corning dish, that gold can go to the second burner of the hot plate into the corning dish evaporating the solution, helping to minimize your volume issues...

I really do not know what material you are working with, as I could not find details in this thread, it can be better to keep the discussions in one thread, with pictures and as much detail as possible, I have a hard time following things spread out in different threads, topics, or different discussions, pictures, and ging clear details are also helpful, the more we understand of the problem the easier it may be to find an answer to that problem.


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## Alabama938 (Mar 8, 2021)

Another fair point

I have 20 chips, I 960, Tried heating in dilute nitric acid twice, and it doesn’t appear that the Kovar was dissolving at all. I rinsed and dry those chips off and let them sit for a few days while I researched straight AR which seems to be a favorite among members for CPUs. I decided to try poormans AR first.

I added the hammer crushed chips to a Tall beaker, covered in 600 mL hydrochloric acid, slowly added 1/2 mole potassium nitrate in a three molar solution to try to dissolve everything. That didn’t seem to be enough nitrate to dissolve all the metals before I had to go to bed adding it in 4 to 6 mL increments. So the solution was allowed to cool overnight and this morning had a negative stannous test on filter paper and in a white spoon.

That’s why the question about decanting a not pregnant solution, to use fresh reagents. The question about sulfamic acid comes from this forum as a possible denoxer(sp?) for HNO3 and I read some stuff about using it to remove free nitrates from lake water, 
Which made me think it could help neutralize extra (K)nitrate ions in solution…

If the free nitrate ion is occasionally changed into nitric acid by the hydrochloric acid, a decent solution of sulfamic should gobble that up and drive the reaction forward, but it seemed like something that might be slower than with the actual acid.

I was trying to find a safe and cost efficient way to process e-waste, I also have a decent sized batch of acid peroxide cooking with a bubbler. I have the ability to acquire a large amount of fingers and CPUs for free and I wanted to see if this was something that I could pull off, and it sucked me in.

I really appreciate all the time you guys spend considering in typing responses, your experience is an invaluable resource!

Roll Tide


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## butcher (Mar 9, 2021)

If you only have very a slight excess of nitric acid in solution, which is keeping you from precipitating your gold (which actually would mainly be just the unreacted Nox gases left in solution), then you can overcome the NOx gas keeping the gold dissolved, by adding more SMB and drive the reaction to the right of the equation.

Here the SMB is not very good at de-NOx-ing a solution but it can help to drive the reaction towards the right, by helping in removing active gases of NOx.
If you have overused nitric and have much left in the solution then adding an excess of SMB will do little, to almost no good, to get your gold to precipitate effectively, as it is not good at removing free nitric acid from the solution.

Ferrous sulfate can more effectively remove free nitric and actually de-NOx the solution, and precipitate gold.

FeSO4 will actually react with the free nitric acid in solution to decompose the free nitric acid and to de-NOx the solution and reduce the gold back into a metal powder form.

SMB in excess can help to drive off a little NOx gas from solution but is really not effective to destroy much free nitric in solution to any extent.

Both will precipitate gold if the solution has the free nitric eliminated.

ferrous sulfate or copperas will work to precipitate with some free nitric involved where SMB would not work to remove all of the excess nitric involved.


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