removing gold from copper?

[cejohnsonsr1]

We do not all live in the US you know.

Hard to believe that a product as ubiquitous as hydrogen peroxide could be very expensive. At least in any developed country.

 

[Yggdrasil]

Hard to believe that a product as ubiquitous as hydrogen peroxide could be very expensive. At least in any developed country.

I can buy 49% in 25 liter cans for 160 USD.
I haven’t even seen 3%
The problem is not that it is expensive or hard to produce, it is considered a precursor in high concentration and in low concentration bleach do a better job.
And for our use, an air pump is even cheaper, especially in the long run.

 

[cejohnsonsr1]

I can buy 49% in 25 liter cans for 160 USD.
I haven’t even seen 3%
The problem is not that it is expensive or hard to produce, it is considered a precursor in high concentration and in low concentration bleach do a better job.
And for our use, an air pump is even cheaper, especially in the long run.

That price scales about the same, but you wouldn’t need 25 liters and 49% would probably be way past the point of diminishing returns. Are you telling me you don’t have a neighborhood pharmacy or grocery store that sells basic 1st aid supplies? 3% peroxide should be available almost any place you can buy bandaids.

 

[Yggdrasil]

That price scales about the same, but you wouldn’t need 25 liters and 49% would probably be way past the point of diminishing returns. Are you telling me you don’t have a neighborhood pharmacy or grocery store that sells basic 1st aid supplies? 3% peroxide should be available almost any place you can buy bandaids.

That is why I haven't bought it in bulk, I found a 100ml bottle of 10% at a pharmacy and they demanded 15 USD so I dropped it.
We use different substances here, mostly something called Chlorhexidine.
There may be at hairsaloons, but frankly I haven't checked them, since I don't need it.

 

[kurtak]

I don’t know the exact ratios, but I used to put about a gallon of Muriatic in a 3 gallon bucket filled with fingers and 3 liters of peroxide to get it started. Then another liter of peroxide every 2 days to freshen it up

I am sorry but using that much peroxide (about a gallon) mixed with a gallon of HCl will most certainly dissolve some gold - even with the peroxide at only 3 percent

As long as there’s any copper left, no gold will dissolve due to copper being higher on the list of reactivity. For the amounts we’re discussing there’s really no danger of dissolving gold.

I am sorry but that is not how the reactive series works

It is NOT selective to just one metal because that one metal happens to be higher in the series

If you have more then one metal involved - & all of those metal will react with a given acid (or oxidizer) the acid/oxidizer WILL react with ALL of those metals

It's just that the acid/oxidizer will react more with the metals higher in the series & less with the metals low in the series

Because the acid/oxidizer reacts with all the metals the higher reactive metal will cause whatever lower reactive metal that is dissolving to cement back out - that is called a redox reaction

With that much peroxide you are more then likely dissolving at least some gold - you just don't know it because gold being so low in the series the oxidizer is working on the gold - just much less then on the copper - so it's not dissolving all the gold --- the small amount of gold that is dissolving is then cementing out on the copper & again you just don't know it because the amount of gold you are dissolving is small in the first place under these conditions

Kurt

 

[cejohnsonsr1]

That is why I haven't bought it in bulk, I found a 100ml bottle of 10% at a pharmacy and they demanded 15 USD so I dropped it.
We use different substances here, mostly something called Chlorhexidine.
There may be at hairsaloons, but frankly I haven't checked them, since I don't need it.

$15 for 100ml? I wouldn’t pay that. Still can’t understand why something like peroxide would be so expensive. What country?

 

[cejohnsonsr1]

I am sorry but using that much peroxide (about a gallon) mixed with a gallon of HCl will most certainly dissolve some gold - even with the peroxide at only 3 percent

I am sorry but that is not how the reactive series works

It is NOT selective to just one metal because that one metal happens to be higher in the series

If you have more then one metal involved - & all of those metal will react with a given acid (or oxidizer) the acid/oxidizer WILL react with ALL of those metals

It's just that the acid/oxidizer will react more with the metals higher in the series & less with the metals low in the series

Because the acid/oxidizer reacts with all the metals the higher reactive metal will cause whatever lower reactive metal that is dissolving to cement back out - that is called a redox reaction

With that much peroxide you are more then likely dissolving at least some gold - you just don't know it because gold being so low in the series the oxidizer is working on the gold - just much less then on the copper - so it's not dissolving all the gold --- the small amount of gold that is dissolving is then cementing out on the copper & again you just don't know it because the amount of gold you are dissolving is small in the first place under these conditions

Kurt

Maybe in theory. In practice I’ve never put a single atom of gold into solution with this method. It performs just as I described and took 7-10 days to complete the process.

 

[Yggdrasil]

$15 for 100ml? I wouldn’t pay that. Still can’t understand why something like peroxide would be so expensive. What country?

It is beside the point.
The price is used as a deterrent for the ones (my guess) that can't source it by industrial/professional routes.
This is in Norway, but i guess it is more or less the same around here.
The point is, that for most it is cheaper to use air bubbling and the risk of inadvertently dissolving some of the Gold disappear.

 

[kurtak]

Maybe in theory. In practice I’ve never put a single atom of gold into solution with this method. It performs just as I described and took 7-10 days to complete the process.

Per the bold print - what make you so sure about that

Kurt

 

[Yggdrasil]

Per the bold print - what make you so sure about that

Kurt

I kind of agree if we are following the science, as we should strive to do
Even washing with soap will dislodge single atoms and as such put them “into” solution in a 0 valence state as colloids.
But since there is an oxidiser in play, there will most certainly be measurable quantities of Gold dissolved.

Anyway it may be hard to get to them and the amounts will be miniscule since they for the most part will cement out on what ever base metals is available at any given time.
So I agree with Kurt here

 

[kurtak]

Maybe in theory.

There is no theory about it - it is a scientific fact (what I posted yesterday)

Acids/oxidizers don't have a mind of their own where they "decide" - I am going to work on this metal - but not on this other metal

Rather - they work - more - or less - on the metal(s) according to the metal(s) place in the series

If I put a copper coin a silver coin & a palladium coin in a beaker with nitric acid the acid is not going to "decide" to work on just the copper because it is the most reactive of the 3 metals

Rather - it is going to work mostly on the copper - also on the silver but less then on the copper - also on the palladium but less then on the silver &/or copper

So - if HCl + H2O2 will dissolve gold - it will dissolve gold whether there is copper in with the gold - or not

Kurt

 

[Shark]

If we place fingers in CuCl2 (AP) it eats the copper out from under the gold layer. If enough oxygen is introduced it starts working on the other metals, gold on the fingers. It will cement the gold back out and and leave this as powders in the solution along with the foils. Excess oxidizer will leave a larger amount of powders than when using an air bubbler such as an aquarium pump because it adds a lower amount of oxygen than an oxidizer, such as peroxide, but provides an aggressive amount of stirring action to the solution. If we use filter papers to capture the foils from AP then the powders are a minimal loss of gold. If we strain the foils through a coarse filter such as a colander then the loss becomes more noticeable. Proper clean up of our waste stream will return these losses but then we don’t know how much came from which batch. The real down side to using large volumes of peroxide is the increased volume of waste for the smaller volume of gold being processed.

All that being said in the simplest terms makes sense to many who aren’t good with the science of what we do, but this does not discount the science of it. Knowing the science can greatly aid when things go wrong and we are trying to fix the problem. I believe that when I want to learn something I am better served by knowing as much as possible. I struggle with the scientific terms at times due to some memory issues and tend to use over simple terms. I can understand a fair bit of the formulas and read them fairly well. I struggle hard to get it back out of my head and back into writing, hence the simple wording.

We need an open mind to learn, if we close our mind we don’t loose the ability to learn we shut it off. Turning off our own ability to learn is much worse than loosing that ability.

 

[cejohnsonsr1]

Per the bold print - what make you so sure about that

Kurt

The stannous test. No reaction. No gold in solution.

 

[cejohnsonsr1]

There is no theory about it - it is a scientific fact (what I posted yesterday)

Acids/oxidizers don't have a mind of their own where they "decide" - I am going to work on this metal - but not on this other metal

Rather - they work - more - or less - on the metal(s) according to the metal(s) place in the series

If I put a copper coin a silver coin & a palladium coin in a beaker with nitric acid the acid is not going to "decide" to work on just the copper because it is the most reactive of the 3 metals

Rather - it is going to work mostly on the copper - also on the silver but less then on the copper - also on the palladium but less then on the silver &/or copper

So - if HCl + H2O2 will dissolve gold - it will dissolve gold whether there is copper in with the gold - or not

Kurt

The point is that we’re not using nitric and we’re not using enough peroxide to dissolve gold even if it were the only metal in question. It will, however, accelerate the process of dissolving enough of the copper to release the gold.

 

[kurtak]

The stannous test. No reaction. No gold in solution.

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

 

[cejohnsonsr1]

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

Hence my reference to the reactivity of metals previously. If any gold is being dissolved, and I don’t concede that there is, then it isn’t in solution and, equally important, it’s not in the filter. Since that’s the only 2 places it could be, it hasn’t dissolved. And that is the difference between theory and practical application.

 

[Yggdrasil]

Hence my reference to the reactivity of metals previously. If any gold is being dissolved, and I don’t concede that there is, then it isn’t in solution and, equally important, it’s not in the filter. Since that’s the only 2 places it could be, it hasn’t dissolved. And that is the difference between theory and practical application.

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.

 

[cejohnsonsr1]

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.

My point was that if it’s not in solution and not in the filter then it didn’t dissolve.

As an aside, I got curious about the price of peroxide in Norway so I did a little research. When you 1st told me how expensive it was I was a little skeptical. Now I’m just shocked and I still don’t understand why it should be so expensive there. What makes something so common and cheap here so expensive there? I don’t get it.

 

[Yggdrasil]

My point was that if it’s not in solution and not in the filter then it didn’t dissolve.

As an aside, I got curious about the price of peroxide in Norway so I did a little research. When you 1st told me how expensive it was I was a little skeptical. Now I’m just shocked and I still don’t understand why it should be so expensive there. What makes something so common and cheap here so expensive there? I don’t get it.

I tend to disagree, it just means it don't stay in solution.
As a business you can get it relatively "cheap", not as a private citizen.

 

[cejohnsonsr1]

I tend to disagree, it just means it don't stay in solution.
As a business you can get it relatively "cheap", not as a private citizen.

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.