AP. What Did I do Wrong?

We are newbie’s. We’ve got bunch of computers but no chemistry experience so we decided to try the acid peroxide from the General Reaction List first.

“4. AP= Acid Peroxide = 2 Parts Muriatic Acid, 1 Part 3% Hydrogen Peroxide. Dissolves base metals, slowly dissolves gold when heated. If gold is present drop with SMB, NO urea needed.”

So we took 1 oz of fingers and put them in a dish with 200 ml of 32% muriatic acid and 25 ml of 6% hydrogen peroxide – it started turning green within a few minutes.

We also took another ounce of fingers and put them into 200 ml of 20% muriatic acid and 25 ml of 6% hydrogen peroxide it also started to turn green but took longer.

We left them for the rest of the day and watched as the gold foils lifted. We left them for two days and the foils were completely dissolved. We then added the two dishes together and got rid of the ‘empty’ fingers filtered the green liquid which left no residue in the filter paper.

Then we added a teaspoonful of SMB and noticed some fine bubbles and a small amount of black stuff forming in the bottom of the dish, when the reaction seemed to slow down we added some more SMB a couple of times and gave it a stir. At some point the solution turned a rich brown colour and gave off a very strong SMB smell that nearly took my head off. (And 8 hours later as I write this, I can still taste it and I have the sniffles like a cold). After that, every time we added SMB we got a more violet reaction.

I left it for a couple of hours, then took some water in another dish and a added about 100 ml of the liquid in the belief that maybe the HCl was too strong and was re-dissolving the gold and ‘fighting’ the SMB, I ended up with a nice yellow liquid like Auric Chloride in LaserSteves video so I added some SMB – nothing!

There is gold in the original liquid and the diluted liquid obviously but I/we have missed something. Can anyone help? What do I do next or next time? We have another batch on the go.

Linton.

I wold love to see the answer to this one as I am thinking of using the AP method myself as it seems the safest way to start down this path of danger.

You need to test with Stannous Chloride for dissolved gold before you add any SMB. There may not be any.

If you have dissolved gold in the AP instead of SMB you can continue to reuse the AP on more fingers until it is saturated with copper at which point your gold will be pushed out of the solution as a sediment.

A few mistakes there I see to start.

You really need to process more that an OZ of fingers at a time to really drop any gold to speak of from the solution. But before that let’s back up.

To start with the AP process is mainly used to dissolve the base metals from under the gold so it can be release from the board and you are left with the foils which are fairly pure in there gold form. This far you had got it right. At that point you need to filter the foils from the green solution because the green is where your copper dissolved into the hcl. By pouring the two mixtures together you just added the trash ( Copper ) in the acid to the other acid you had from the other batch. So now you had two solution of Copper which was still alright up until this point.

Your problem came when you allowed the foils to remain in the solution and dissolve into the same trashy mixture you just worked so hard to separate it from. So if your gold does drop it is going to drag down copper with it and make your precipitated gold dirtier that necessary. Your gold foils that you had should have been filtered from the solution and then run thru the bleach / hcl method to dissolve the foils in a much cleaner state being as how the foils are almost pure gold, compared to the solution you now have that is contaminated with all them base metals.

AP is only intended to remove the base metals ( Copper ), But if you add enough peroxide to it to fast it will dissolve everything including your gold. But when you add it in very small increasements you are able to control the rate of dissolution to which the metals dissolve. Another thing would be to use a higher percentage hydrogen peroxide like that you can get from a pool supply store. The lower percentage stuff has more water . So the more you add, the more water you add to the solution weakening it in strength. This is also true with the lower percentage strength Hcl (muriatic acid ) you added. That's why the other dish took longer to dissolve. After AP the foils go into the Clorox / hcl method. Then you can drop with SMB.

Try watching Steve’s vid's again with all this in mind. The term refining means to separate one metal from another Or as we say around here Garbage in - Garbage out. To test for gold in there put a drop or two on a filter that is white then test by adding a drop of Stannous Chloride watch for the color change from violet to purple the strength of the color will give you an idea to the strength of the gold in solution. If the gold is there you have not lost it you can still back up and start over again.

Hope that helps. I think I got it alright. If I made a mistake someone will correct me.

good answer

This might help to explain some things also :arrow: :arrow:

This post was made by Badastro


Here are some chemistry lessons:

Any solution containing chlorine ions is capable of dissolving gold.

Oxygen from the air can get absorbed into HCl and oxidize gold. The gold ions then form complexes with the chlorine ions to give auric chloride.

The truth is a very tiny amount of gold will dissolve in HCl until all available oxidizers are used up. This amount may not be detectable.

Acid peroxide is just a weak form of aqua regia. Aqua regia works by having the nitrate ion oxidize gold as ions and allowing chloride ions to form complexes. This is why you don't need nitric acid to make a gold dissolving solution: just use sodium nitrate (which is an oxidizer) for poor man's AR. Those brown fumes come from the nitrate ions being reduced by the gold as the nitrate ion gives up oxygen to become NO.

Acid peroxide is the same idea. Instead of nitrate as an oxidizer, you're using hydrogen peroxide, which is also a powerful oxidizer. The hydrogen peroxide oxidizes the gold and the chloride ions form soluble complexes. Also happening is the dissolution of oxygen into the acid, which helps dissolve gold.

Nitric acid will actually dissolve a tiny undetectable amount of gold into ions, but since gold will not form soluble compounds with the nitrate ion, the gold does not continue to dissolve.

The reason why nitric acid will dissolve base metals such as copper very fast while hydrochloric acid will not dissolve it fast is because HCl is a non-oxidizing acid.

HCl cannont oxidize copper metal into an ion so the copper stays intact. It will react with oxides of copper forming water with the oxygen and hydrogen ion leaving a copper ion to form a compound with the chloride ion. If there is oxygen in the air that can dissolve into the acid, then that dissolved oxygen can oxidize the copper which then forms compounds with the acid. In effect, the acid makes the copper corrode from the air faster because the chlorine is stripping away the protective oxide layer.

Nitric acid is different because it can oxidize copper. The nitrate ion plays a dual role. Free nitrate ions give up oxygen to oxidize copper. The oxidation of copper simultaneously reduces the nitrate ion into nitrogen monoxide gas. Free hydrogen ions combine with oxygen to form water and free nitrate ions combine with the copper ion to form copper nitrate.

The reason why AP is prefered over AR is because it doesn't give off horrible fumes. Gold is least likely to dissolve in both AR and AP, but each metal does not dissolve precisely sequentially. There is some overlap. Galvanic action can help make the process more sequential, but not everything is electrically connected so it doesn't happen effectively.

You can in theory dissolve base metals only with aqua regia by controling the amount of nitrate ions you put into the acid. The reason why AR dissolves everything is because we make it such that it will dissolve everything, but if we limit the amount of nitric acid or NaNO3, then we mimick the effect that acid peroxide does.

AP will dissolve everything like AR does if and only if you put in wayyyyyyyy too much peroxide without diluting it too far. It will take a long time but it will happen.

When an AP batch is done, the reason why gold flakes remain is because the oxidizer is all used up, and gold chloride displaces base metals and gets deposited as a black powdery film.

:arrow: http://goldrefiningforum.com/phpBB3/viewtopic.php?t=808&postdays=0&postorder=asc&start=0

Brilliant answer – thanks Palladium and qst42know.
As I mentioned I have two more batches on the go and I checked these today. The two batches are as follows:-

½ lb of fingers in 400ml HCl 32% + 50ml of 6% H2O2 and
½ lb of fingers in 400ml HCl 20% + 50ml of 6% H2O2

I took each batch and tested them with stannous and there was no gold in the solutions, by which I mean is the stannous test proved negative, however, there was lots of bits of gold floating around in the solution so I filtered each batch retaining the solution and then returned the solution to the dishes.

I treated each batch separately.

I then took the fingers and washed them in water and with a spay bottle and filtered the results (water and foils) through the same filters respectively. Not all of the fingers had completely lost their gold so I returned them to their respective dishes and added about a table spoon of H2O2 to each. (I don’t if that was a good thing to do but I did it)

Now I have two filters with gold foils in and two dishes that are still producing more foils.

Now what is interesting is that one batch produced more foils than the other and because there are two people working together here, I’m not sure which is which.

Having spoken tonight with TonyD, he is certain that he put the 32% HCl in the ‘silver bucket and the 20% HCl in the ‘green bucket’. The ‘green bucket’ is out out-stripping the silver one (pardon the pun) – this is counter-intuitive. Any thoughts?

Questions:-

1. Green bucket/ silver bucket thing.
2. How do I keep a vat of AP foil producing liquid going? Do I add more acid or more Hydrogen Peroxide? I’m thinking about LazerSteve’s two buckets, one sits inside the other. The inner one is a sieve. The outer one contains the AP.
What about draining and filtering the outer bucket solution with the foils, filtering the foils and returning the (spent?) AP back into the inner one, add more acid/peroxide/fingers etc. and just repeating the process.?

Linton.

This should help explain some more

:arrow: Reuse of HCL
http://goldrefiningforum.com/phpBB3/viewtopic.php?t=1645&postdays=0&postorder=asc&start=0

Questions:-

1. Green bucket/ silver bucket thing.
:arrow:
I have several gallons of 35% H2O2, but I still use the weaker 3% stuff in my AP. The main reason is for the extra water. The water allows the Copper II Chloride to become mobile in the solution and keeps the rejuvenation cycle going. The other main problem with the concentrated stuff is that you end up dissolving your gold along with the base metals due to the excessive amount of chlorine produced.

If you think about the etching reaction you will realize that the active ingredient is the copper II chloride, not the peroxide or the muriatic acid. With this in mind the water is necessary to allow the exchange of the copper metal ions in liquid form. If the solution becomes saturated due to lack of solvent (water), the copper won't convert to from the deactivated (and insoluble form) of copper I chloride back to the soluble desirable form (copper II chloride). If you find a lot of off white to gray colored sludge in your batches you are producing copper I chloride. It becomes discolored by the saturated etching solution which appear very dark brown in color and very thick.

Here's the overview of the chemistry:

pcbfab.com wrote:

Hydrogen Peroxide as a Replenisher

The Hydrogen Peroxide H202 system of replenishing has been unpopular in the PCB industry, for no outstanding reason, but not in the closely related Photo-Chemical Milling industry. Perhaps the real reason why it is not popular, is that a reliable control system, for both components required to replenish the system, Hydrogen Peroxide, and Hydrochloric Acid, has only recently become available. Previously, it was probable that those people who took on the challenge of devising their own control system would likely have chosen the least expensive, and easiest system to control replenishment system, which is the Chlorine system. The overall etch/replenishment reaction for Hydrogen Peroxide is:

H202 + Cu* + 2HCl -- CuCl2 + 2H20

The use of Hydrogen Peroxide also produces a purer Cupric Chloride, without Sodium Chloride (NaCl) impurities, but the Hydrochloric Acid level must be carefully monitored, as it is consumed in the regeneration part of the reaction. This replenishment method also suffers from the fact that over-replenishing with the Hydrogen Peroxide can generate free Chlorine gas.

The fact that the replenisher ingredients are supplied in water solutions, as well as the fact that the replenishment reaction produces water, limits the maximum Cupric Chloride content of the etch, but it is still possible to get to as high as 40* Be', depending on the concentration of the Peroxide and HCl replenishers.

..

Just like the Cupric Chloride etchant, the Copper that is already in solution in the etchant, dissolves the copper metal on the board.

Key things to remember to sort this explanation out:

1. The metal is dissolved by being "Oxidized", which means that it loses electrons, which changes it from the orange metal to a water-soluble blue compound.
2. The electrons are initially removed from the Copper on the panel by the copper that is already in solution. This seemingly unlikely idea can only happen because copper can exist in 3 forms:
1. Orange Metal - copper with a "correct amount of electrons"
2. Cupric salts, Cu++ (blue) -- copper missing two electrons. This is the blue, water-soluble form we are all familiar with.
3. Cuprous salts, Cu+ (white) -- copper missing one electron, or half way between form 1. and form 2. This form is usually insoluble, unless it is chelated, and is not often seen in a board shop in large amounts.

The actual etch reaction is:

Reaction 1.
Cu* reacts with Cu++ to give 2 Cu+

The cuprous salts are then (supposed to be) immediately oxidized (electrons removed) by the Oxygen in the air which is being pulled through the etcher. In the process, the spent Oxygen is converted to water. (See reaction 2.)

Reaction 2.
2 Cu+ + 0(air) + 2 H+ -- 2Cu++ + H20



I find the extra water is to an extent is helping, not harming. I think the optimal amount of water is just enough to hold the copper II chloride that you need to etch the proper amount of copper off of the scrap.


Steve

A fish tank air pump can keep it working (oxidizing) and the bubbles can help dislodge the foils.

Also from your post where you explained your first experiment it seems to me that you added too much SMB to your AP batch. I think that I saw here on the forum that you have to put that much of SMB as much of gold is expected from solution.

Ok I am going to go for the AP method but I want to ask a couple of questions first just to make sure my mind has all the info corrct.

first: SMB, does that stand for sodium metabisulfite ? aka bondie stump remover

Second: this is the steps in the order I have interpited from reading

1: 200 ml of 20% muriatic acid and 25 ml of 6% hydrogen peroxide
For the peroxide will a 12% clairol bleach kit work or is their somthing I can get from a pool store?
2: add gold
3: let base metals disolve
if thier is silver in the solution after step 3 what can I use to get the silver out?
4: pour off solution and wash gold.
5:make a new AP, disolve gold this time
6:use SMB to precip the gold out in a refined form after wahing the gold melt it
7: once all PM'S are removed add baking soda to nutralize solution and dump

Did I miss anything?
In the end I will have to use AR cause the main goal here is to get plat from cat cons but I do have a bunch of electronics with gold so why not . Just to get it out thier I am not a Cat Con Crook, My friend owns a auto salvage yard and knows others that do as well and he can get me all of them I want.

I am going to build a fume hood that takes the funes into a big container and it will be drawen thrue the water in the drum that will have some nutralizer like baking soda or urea.
I need to make sure I got somthing in the drum that will nutralize all of the bad stuff that comes out of AP, i dont want to release anything bad into the air for me my kids or my neihbors to breath,any suggestions?

Thanks you guys!

I have now several filters with gold foils in and a few more batches on the go – one of them with 4 lbs of fingers. My next step is to make Auric chloride using the ‘Clorox’ process. We don’t have Clorox over here in the UK but I have found a similar brand which is 5% sodium hypochlorite and is described as thin bleach.

Before I begin the process I have a few questions;

1. I have been using two strengths of acid (HCl) – 20% and 32% - the 20% seems to work best – (BTW – both work). Palladium, I know your post answered this question but can I ask it again? Does 20% work better than 32% for the AP process?
2. Am I right in assuming that 32% will work better in the Clorox process?
3. When I am filtering, I filter the AP and foils first – keep the AP and return it to the dish – I clean the fingers in fresh water and discard the stripped ones. Then I clean the un-stripped ones with a spay bottle and put the fresh water and foils through the same, or different, filter. On this second pass I have noticed that I sometimes get Gold foils with a grey sludge on top instead of clean gold. What is this grey/green sludge?
4. Can I put these (the foils with a bit of sludge) through the Clorox process as they are? Or should I put them through the AP again?
5. Can I put the ‘clean’ filter papers into the Clorox solution as they are or scrape out the gold and keep the filter papers for a separate process?

Linton

Astraveller said:

1. I have been using two strengths of acid (HCl) – 20% and 32% - the 20% seems to work best – (BTW – both work). Palladium, I know your post answered this question but can I ask it again? Does 20% work better than 32% for the AP process?

Click to expand...

A little extra water won't hurt the AP process, it may even help to keep the gold foils from dissolving if too much or too strong of a peroxide solution is used.

Astraveller said:

2. Am I right in assuming that 32% will work better in the Clorox process?

Click to expand...

I would use the 32% for sure. The 20% will work, but will retain more chlorine gas due to the extra water. This dissolved chlorine will help the gold foils dissolve, but any extra after the foils are gone will need to be removed with heating.

Astraveller said:

3. When I am filtering, I filter the AP and foils first – keep the AP and return it to the dish – I clean the fingers in fresh water and discard the stripped ones. Then I clean the un-stripped ones with a spay bottle and put the fresh water and foils through the same, or different, filter. On this second pass I have noticed that I sometimes get Gold foils with a grey sludge on top instead of clean gold. What is this grey/green sludge?

Click to expand...

The combined foils from the filters and the bottom of the bucket should remain in the reaction bucket until they are thoroughly washed free of the gray sludge (copper I chloride). The CuCl is washed out using HCl followed by water after all the gray sludge is gone. Once the gray sludge is removed and the foil wash water is 100% clear then transfer the foils to the filter or better yet, directly to the clorox reaction beaker.

Basically after filtering the AP solution wash the foils that were caught in the filter back into the mash of foils in the bottom of the bucket. Then wash all the foils together with HCl then water.

Astraveller said:

4. Can I put these (the foils with a bit of sludge) through the Clorox process as they are? Or should I put them through the AP again?

Click to expand...

No. See above.

Astraveller said:

5. Can I put the ‘clean’ filter papers into the Clorox solution as they are or scrape out the gold and keep the filter papers for a separate process?

Click to expand...

The filters should be washed down into the reaction bucket with the main foil mash and washed with HCl and water. After this the clean foils are transferred directly to the clorox reaction beaker. The filters go in your filter burn box.


Steve

Thanks Lazersteve!

Your reply was everthing I needed to know with the exception of one question that I did not ask. Having removed the copper sludge from the foils with Hcl and cleaning them with water - how do I get rid of the water in the (now) Clorox processing dish other than filtering the gold foil mash again?

I feel another 'duh' moment coming on - but, I like those.

TIA.

Linton.

Linton,

Let the foils settle and carefully pour or siphon off the majority of the liquid.

Several rinses of the foils with water won't hurt. If you see any white or off-white sludge appear when rinsing add some more HCl siphon, then water rinse again.

A little extra water in the HCl-Cl reaction won't hurt, just be sure the foils are completely free of base metal compounds and metallic debris.

Steve

Duh!

Thanks Steve.

I now have a good set up for producing gold foils. 4 x 28 Lt transparent stacking boxes with lids. One of which has the bottom cut out and replaced with a plastic mesh that is just fine enough to stop the fingers falling through. This sits in a tub of AP and is occasionally transferred to another tub for rinsing and chasing out the foils with a water bottle. The last tub is used to collect the rinse and stray foils, siphoned off from the first rinse. This tub then becomes the primary rinse tub as the process continues. If that makes sense? What I mean is, the two rinse tubs alternate and the AP tub (rich pickings) is filtered separately.

Your advice for treating my copper sludge filters with HCl worked a treat! I just poured HCl into the filters and they came up bright and shiny. After rinsing, I scooped out the foils as gently as I could and put them into a Pyrex bowl ready for the Clorox process. I cleaned out the filters with a spay bottle over the rinse tub, as best I could, and then saved the filter paper in a place where it could dry out.

After 1 day I have a (very small) fist full of soggy gold foils in a Pyrex dish from the rinse tubs and I haven’t even touched the AP tub yet!

Thank you, Steve (Lazersteve),
And Steve (Palladium),qst42know, patnor1011

If I can figure out how to do it, would you like to see pictures of the set up?

Linton.

I never get tired of the photos :wink:

How do I post pictures? I tried but I didn't succeed. I'm a fast learn - throw me a bone.

Linton.

Resize your images to 800X600 and save using one of the allowed file types. At the bottom of the "post a reply" page, click "browse", find your photo and open, then click "submit".