So I'm trying to dissolve gold foils in with HCL and bleach but only some of it has went into solution. I have used the same bleach and the same hydrochloric acid multiple times to dissolve gold. This time it doesn't seem like all the gold wants to go into solution I've tried heat I've tried more HCL and I've tried more bleach before I try anything else I wanted to ask the forum what am I doing wrong?
Gold foils are not dissolving in HCl +bleach
- Thread starter Rreyes097
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Check the pH often, it needs to be acidic, preferably not higher than 1-2.
Do not heat it, the Chlorine will leave the solution faster.
Try to get the Bleach to enter the solution at the bottom. Put the pipette all the way down and empty it there.
HCl/Bleach are not very suited for other than thin foils or fine powder.
Most of the material is: gold plated ribbon, a few pinless CPUs, circuit boards from cell phones, and ram sticks (not the bottom portion but the actual sticks, sometimes they have gold plated dots and whatnot). There's a solid chance there is tin in the solution, could this by chance be the problem? What's keeping the gold from dissolving? I've had other solutions with tin but never had a problem. Stannous says no gold is in solution. I had thought that at least some gold had dissolved but alas nope?
MicheleM
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- May 4, 2020
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Tin? You write "gold foils" , the informations you provide us contradict each other: "gold foils" means that you recovered them, so no tin; "acid and bleach" and "stannous test" negative, at least a minimum amount of gold should have been dissolved. Seriously i don't understand
Your Gold would have cemented out back onto the Copper traces inside the ram sticks, CPUs and so on.
This kind of material is not considered foils until after you have run it through an AP cycle so it is ONLY foils.
Negative Stannous here means either no Gold dissolved or the Gold dissolved and plated back.
What about our other questions?
Let me apologize for my careless words. I was calling them foils because some of what I put in was foils I had from an AP solution that I have on a bubbler and I every couple weeks I filter it for the foils. And lots of the gold has also come off most of the material that's in there. So I have foils on the brain. But yeah my wording was misleading and careless and for that i apologize.
So other than that what else am I missing? Yes I had a lid on the beaker.
What expiration date do the Bleach have?
Have it been stored cold all the time?
Is it evolving gas when it is added to the HCl?
Martijn
Well-known member
Did you read these replies, checked your situation, and replied to his questions?
The expiration date is smeared so I can't see it. But it is old. And yes stored in cool room
Maybe get some fresh Bleach and try then?
Maybe but it was just working the day before. Could those be metals be stopping it somehow?
Something has changed, and if the foils came from what you use to do, it should not be that.
Unless you have mixed in some golden plated things that's not Gold.
Anyway the Gold should dissolve.
Next, your chemicals has changed some how.
What is the pH?
Put the bleach into closet with cleaning stuff and buy pool chlorine instead. TCCA tablets, powder or calcium hypochlorite shock pool chlorine. Setup the chlorine generator and bubble chlorine into the suspension of foils in HCL. Cover the beaker, better perform in some flask with more narrow ending, like Erlenmayer. No dead volume added, quick, effective, no foaming from unknown stuff in bleach/ additives.
And proceed slowly, chlorine don´t have very good solubility in aqueous solutions. And with temperature above room temperature it escapes like crazy. But it is very heavy as gas.
So if you have narrow ending of the reaction vessel, loosely covered with some stopper, you can generate a bit, and let it stir for some time -and chlorine above the solution level will adsorb into the solution over some time. Just then generate a little bit more.
Bleach is voluminous, ineffective oxidant, as purchased like 5% or so solution - which could be much much less as it deteriorate quickly on the shelf either in the shop or at your home. Basic, full of sodium chloride and other crap added by manufacturer. Never recommended from me to anyone for refining. Maybe industrial 12-13% stuff, as it is more than twice as strong, no added junk.
If one wish to "prolong the retention" of the chlorine in the solution, there is possibility to start with HCL and bromide or iodide added. Chlorine easily oxidize them to bromine/iodine/bromine monochloride/ICL and other funky stuff - but more importantly - all of these have higher boiling points and thus better retention in solution. By doing this, you can improve efficiency, and lowering the ammount of chlorine necessary.
Altough, my favourite chlorine precursor is hydrogen peroxide. Very easily dosed from dripping funnel slowly over time, does the job nicely, no added foamy junk from fragrances and stabilizers, no de-NOx-ing necessary... Top oxidant for final gold powder/foils re-refining.
Remeber that hypochlorite and chlorine are strong oxidizers - and thus strong bleaching agents. There are some crappy low end pH papers, which can be badly bleached by this harsh solution, and thus deliver skewed results. Not common, but happened to me once or twice. Little pinch of sodium bicarbonate never lie
Altough I always add excess of HCL and never use basic oxidants which deplete the acid - so no problems Yes I know, but something has changed for the OP.Remeber that hypochlorite and chlorine are strong oxidizers - and thus strong bleaching agents. There are some crappy low end pH papers, which can be badly bleached by this harsh solution, and thus deliver skewed results. Not common, but happened to me once or twice. Little pinch of sodium bicarbonate never lie
I prefer TCCA or Peroxide too, actually never used bleach.
I don’t like the idea of neutralising my acid.
That's what I used to test ph because my ph meter isn't working. So I'm unsure if I'm reading it right. But it was deep purple or better yet maroon?Remeber that hypochlorite and chlorine are strong oxidizers - and thus strong bleaching agents. There are some crappy low end pH papers, which can be badly bleached by this harsh solution, and thus deliver skewed results. Not common, but happened to me once or twice. Little pinch of sodium bicarbonate never lie
I also thought I might have added too much bleach and it did exactly that. Neutralized the HCl. So I did try adding a bit more in but nothing happened.
