removing gold from copper?

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I still don’t understand why peroxide should be so expensive. But to the point, if gold (or any other metal, goes into solution, it must precipitate. So if it’s not in solution and there is no precipitant, then it never dissolved. This ain’t magic. It doesn’t reincorporate back into the foils from which it came. There has to be either gold in solution or a precipitant. If there is neither, then it never dissolved.
No but there are plenty space inside the traces on the PCB and since it is low amounts/concentration what ever precipitates will be very fine, probably too fine for most filters.
You have found a way that suits you and are happy with the results.
 
I still don’t understand why peroxide should be so expensive. But to the point, if gold (or any other metal, goes into solution, it must precipitate. So if it’s not in solution and there is no precipitant, then it never dissolved. This ain’t magic. It doesn’t reincorporate back into the foils from which it came. There has to be either gold in solution or a precipitant. If there is neither, then it never dissolved.
Our government has found that adding ludicrous amount of taxes on products that are legal but they don't like is an effective way of controlling the market.
Tobacco, Alcohol, gasoline and so on.
 
Our government has found that adding ludicrous amount of taxes on products that are legal but they don't like is an effective way of controlling the market.
Tobacco, Alcohol, gasoline and so on.
Well you have my sympathy. I guess I really do understand after all. I hope you had a Merry Christmas and I wish you a Happy New Year.
 
No but there are plenty space inside the traces on the PCB and since it is low amounts/concentration what ever precipitates will be very fine, probably too fine for most filters.
You have found a way that suits you and are happy with the results.
I didn’t use whole boards. I used closely trimmed fingers. If any metal can’t be detected by any means, it isn’t there.
 
Prices and availability of what Americans would consider household chemicals vary widely in the world. In much of the EU there are several layers of taxes that most there are not even aware of. The VAT is just the most visible. Most of these taxes are designed to do as Yggdrasil says: control access through price.

Time for more coffee.
 
Prices and availability of what Americans would consider household chemicals vary widely in the world. In much of the EU there are several layers of taxes that most there are not even aware of. The VAT is just the most visible. Most of these taxes are designed to do as Yggdrasil says: control access through price.

Time for more coffee.
Yeah. When he put it in those terms I understood perfectly.
 
It will dissolve and then cement out, where it cements out is out of our control.
It will not be much, but I see no reason in throwing it away anyway.
The way to test this is to do a stannous test on the wash fluid when it is decanted from the
That is because the gold that is being dissolved by the HCL + H2O2 is being cemented back out of the solution by the copper (the redox reaction I mentioned the other day)

Redox is a reaction where both oxidation & reduction take place at the same time

Redox happens when two (or more) metals can be oxidized by the same oxidize - but one metal is more reactive then the other metal

It happens because though the oxidizer can work at dissolving more then one metal - at the same time --- the more reactive metal (copper) will cause the less reactive metal (gold) to be reduced - just as fast as that less reactive metal is being oxidized

in other words - due to the redox reaction - the copper is preventing the gold from staying in solution - therefore - because the gold is being reduced as fast as it is being oxidized - it (the gold) will not show up with a stannous test because the gold is not staying in solution due to copper cementing the gold (redox)

The cemented gold is going to be ultra fine gold particles & likely washed away when washing the chem out of the (remaining) gold foils

Kurt
The way to prove or disprove this is to let the wash fluid settle after it is decanted from the foils. Reduce it and add it to aqua Regia then do a stannous test. If fine particles were present in the wash they would now be in solution.
 
o.0 its a process currently used to make and refine gold... I just didn't know the exact terminology. Nothing is impossible!
Dunning-Kruger effect is especially dangerous in physical science like chemistry or metallurgy, those branches of science where it is quite easy to cause harm to both oneself and others. If someone doesn't understand why some thesis in science cannot be explained in 2-3 words or get a simple unambiguous answer to an incorrectly asked question, the only reasonable recommendation is to learn from scratch. But actually, those who like simple solutions don’t like complex advice.
goldsilverpro said:
What you want to do is impossible. Don't waste your time. Study the forum.

I would make a small adjustment. Learn the basics of metallurgy and metal physics before reading the forum. Having at least basic knowledge about the physics of alloys will significantly help to separate the “possible” from the “impossible” in experiments.
 
Hello
Let me tell you my understanding and experience of dissolution of Au during the AP procedure:
CuCL2 and HCl will not dissolve Au but only Cu metal and other less noble metals like Zn,Fe,Al... by the following redoxreaction Cu2+ + Cu = 2Cu1+. This Cu1+ is existent in solution as a dark brown (CuCl2)- chlorocomlpex. Cu2+ in diluted HCl is a green chlorocomplex. So when you watch the reaction of gold covered copper in AP the brignt green solution becomes slowly dark brown. Now you have to add an oxidising agent in order to reoxidise all the Cu1+ into Cu2+ to continue the dissolution of copper. And dont forget adding additional HCl if necessary because the new formed Cu2+ ions need their corresponding chlorine anions. And especially be carefull when you add the peroxide because it should only oxidise the Cu1+ in the solution and not attack the noble metal Au. How to do this I recomend the following procedure:
Decant the brown solution into an other container (without any residue) and add slowly under stirring in small amounts the peroxide (ml wise for 3% or dropwise for 30% HP) until the solution is bright green again and not any more HP. An excess now would be able to attack Au (very much slower than Cu). If unfortunately Au is attackted, then Au ions are in the solution and can exist there as long as free HP is present. As soon as all HP is eaten up by the Cu1+ ions, than Au ions are no more stable in solution and will be reduced with a reducing reagent for Au (here mainly the metallic Cu) that means on the Cu surface (not in solution) there is again a redoxreaktion (cementation) between Au and Cu. Au ions and Cu metal are changing electrons forming Au metal and Cu ions.
So as soon as the solution has a little or strong brown color, there is no attack at gold.
Not soluble is not very very correct I should better say something like neglectible. Please take into account that a very small amount of Au is soluble in seawater (some micrograms per cubicmeter).
 
Hello
Let me tell you my understanding and experience of dissolution of Au during the AP procedure:
CuCL2 and HCl will not dissolve Au but only Cu metal and other less noble metals like Zn,Fe,Al...
Copper chloride significantly catalyzes the reaction of dissolving gold in chloride solutions.
 
Copper chloride significantly catalyzes the reaction of dissolving gold in chloride solutions.
Thanks for this remark. It helps me understanding, that sometimes during an AP procedure very small gold particles disappear after adding HP (in order to reoxidise Cu+ into Cu2+).
So in my opinion what happens? I insist in saying the mixture of CuCl2 and diluted HCl is not able to oxidise (dissolve) gold but it catalyses a possible oxidations reaktion of gold (oxidising reagents are for instance AR, HCl + H2O2, HCl + KClO3) that means the velocity of gold dilution is increased or something like this (it is a question of kinetik). This oxidation reaction of gold will happen, when you add more HP than necessary for the complete oxidation of Cu+ to Cu2+ and this excess of HP in the milieu of diluted HCl now will attack the gold as long as the HP excess is not eaten up by the new built Cu+.
 
Thanks for this remark. It helps me understanding, that sometimes during an AP procedure very small gold particles disappear after adding HP (in order to reoxidise Cu+ into Cu2+).
So in my opinion what happens? I insist in saying the mixture of CuCl2 and diluted HCl is not able to oxidise (dissolve) gold but it catalyses a possible oxidations reaktion of gold (oxidising reagents are for instance AR, HCl + H2O2, HCl + KClO3) that means the velocity of gold dilution is increased or something like this (it is a question of kinetik). This oxidation reaction of gold will happen, when you add more HP than necessary for the complete oxidation of Cu+ to Cu2+ and this excess of HP in the milieu of diluted HCl now will attack the gold as long as the HP excess is not eaten up by the new built Cu+.
HCl and Peroxide do indeed dissolve both Au,Pt and Pd.
That is why we do not recommend using Peroxide when using the so called AP etching.
We recommend using an air bubbler, for instance from an aquarium.
 

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