# How to deal with this fun...



## Beirdo (Jun 21, 2012)

I have a pile of CPUs (P3, P4) with the pins removed. About half of them, I hand-removed the capacitors with a hot-air rework station setup. The other half, I did not. I removed all of the plated copper caps from the processors so all that is left is the fiber board and the IC itself.

The half with the capacitors, I have dissolved off the solder with hydrochloric acid (32%), and this has removed the capacitors as well, of course. The result is hydrochloric acid with black precipitate (and a fair amount of it) and capacitors in the dregs... and a nice purple hue. That is where my mind went "Oh crud!".

I filtered off the solids, and have a nice bottle with amethyst-hued purple solution in it. I then went to wash the precipitate with water, and it instantly went from black to a nice milk white, and is settling over the day now.

Here is what I think I have:
- purple solution = HCl + stannous chloride + gold stannate (from the wee bit of gold on the surfaces of the processors for pin 1, etc)
- black precipitate in HCl = silver (maybe lead)
which turned into:
- white precipitate in water (likely actually fairly dilute HCl solution) = silver chloride + maybe lead chloride

So, my questions:
1) what are the chances of dropping any gold from the purple solution? I've read that hot sulfuric might precipitate gold from such a solution, but I'm loathe to work with that stuff unless necessary. I'm aware that I may be losing some to colloidal gold here, but there wasn't that much (I thought) in the first place.
2) am I correct on the black precipitate in HCl?
3) I'm assuming that I can separate lead and silver chlorides with the use of hot water to dissolve the lead chlorides. Is there anything else I'm missing here?
4) if there is cupric chloride in the solution (or precipitate) is there a simple way to separate it?

I'll go back to continuing to read Hoke, BTW. It is a great read, and there is still much to learn (which I'm sure is still obvious!)


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## gold4mike (Jun 21, 2012)

You'll have to wait for a response from someone else to get an opinion of what the purple hue's cause is, but HCl alone shouldn't have dissolved any gold, so I don't think you have gold in solution.

If you have (or have what you need to make) Stannous Chloride you can test the solution to be sure.


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## Beirdo (Jun 21, 2012)

Umm, that doesn't make sense to me. Stannous chloride + gold gives purple, exactly the color of my solution. Testing with stannous chloride wouldn't do anything at all. Just maybe make it *more* purple 

I'm pretty sure that the solution is primarily stannous chloride anyways as I was dissolving solder off CPUs, and even lead-free solder is primarily tin. It had to go somewhere.


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## Beirdo (Jun 21, 2012)

Let's see if this will work. Going to try attaching a picture...


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## ericrm (Jun 21, 2012)

something is totally wrong lol
did you use ONLY HCl ,if yes where does it come from???
edit: even better post a picture of your bottle plz


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## Beirdo (Jun 21, 2012)

ericrm said:


> something is totally wrong lol
> did you use ONLY HCl ,if yes where does it come from???
> edit: even better post a picture of your bottle plz



I used muriatic acid from Lowes. Not the "safer" stuff, either. I'm not at home right now, so can't get you a picture for the moment. The MSDS (attached) from the manufacturer clearly indicates 9%-36% HCl (the gallon jug said 32% on it, if I recall correctly), and no other reagents. I didn't dilute it.

To be clear, there were definitely traces of gold sitting in that solution for periods of time, and I'm thinking it may have reacted with the stannous chloride also in the solution (from the tin in the solder dissolving), not dissolved in the HCl on its own.

View attachment mGMA58.pdf


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## goldenchild (Jun 21, 2012)

What happens if you put some of that purple solution on a q-tip and place a drop of clean stannous on it?


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## Beirdo (Jun 21, 2012)

I'll attempt that tonight. I don't expect any reaction at all, but it's worth a try if you think it would show something useful. Again, if there's gold in there, wouldn't that make it go purple, which it already is? But I'll give it a shot anyways  Be a few hours though.


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## Geo (Jun 21, 2012)

its a colloid, nano particles of gold. you cant precipitate it because its already in its metallic state. add twenty ml's of hcl and add some bleach slowly until the color changes from purple to yellow.


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## ericrm (Jun 21, 2012)

geo
you probably right lol(i wont argue with you :lol: , but how did he disolve the gold in the first place?


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## Geo (Jun 21, 2012)

hcl can dissolve gold if the temperature is high enough and its boiling. the boiling action aerates the solution with enough oxygen to dissolve some gold.

cross contamination with a nitrate of some kind. 

there are a few possibilities how it happened, but from the looks of the picture, thats what happened.

silver nitrate/chloride can also look purple if exposed to the sunlight, but it would also have to be in the form of a colloid.


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## goldsilverpro (Jun 21, 2012)

Maybe it's cobalt. Kovar is 17% cobalt.


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## Geo (Jun 21, 2012)

cobalt in solution is blue, right? ive seen cobalt and it always reminded me of copper nitrate.


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## freechemist (Jun 21, 2012)

Co2+, dissolved in concentrated HCl is blue indeed, the solution turning pink on dilution with water.

freechemist


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## samuel-a (Jun 21, 2012)

Geo said:


> cobalt in solution is blue, right?



Depends on pH, may turn pinkish purple if close to 7.

edit: you beat me to it.... :mrgreen:


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## qst42know (Jun 21, 2012)

I think Lou mentioned a long while ago iron could catalyze the oxidation of HCL under the right conditions?

Should this be evaporated to dryness before you attempt to dissolve again?


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## Beirdo (Jun 21, 2012)

samuel-a said:


> Geo said:
> 
> 
> > cobalt in solution is blue, right?
> ...



Heh, well, I'm pretty sure the pH is nowhere near 7. It started as -1.0 (yes -1.0 for 20 Baume HCL which this was!) and I certainly didn't dilute it. Forming chloride salts and of-gassing H2 gas would lower the pH some, but I'm quite sure it never even saw 7.0 at the end of a long dark tunnel. When my digital pH meter shows up in a week or two, I could tell ya for sure


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## Beirdo (Jun 22, 2012)

OK, a new batch of clean stannous chloride is in the making (using about 2.5" of flattened solid core solder that the manufacturer identified as 96Sn/3.9Cu/0.1Ag - it only said lead-free, silver bearing on the package). I will try the purple solution with it first thing in the morning, which should give it ample time to dissolve a significant portion of it. Wonder if I should go back and buy some that's Sn/Sb only (if they have any) to avoid the copper?

The washed (once) white/grey precipitate is being filtered over night and I did a second water wash of the remainder, still nice and white/grey. I forgot I was going to add hot water to separate the lead chloride from the silver chloride... Oops. I guess I should plop the filter back in the dish before it gets a chance to dry. Stupid... I'll heat it up to dissolve out the lead chloride tomorrow, I guess.

One thing I noticed... a pile of the capacitors seem to have almost completely dissolved and look like they are in fact a small metal foil only left (rectangular, so I know it was the capacitors, not any pads on the processors). Now I'm curious what exactly that metal is. Seems to be too much to possibly be palladium. If it is, I will be most happy. hehe. Another use for the stannous tomorrow, I guess. I'll try to take a picture of them tomorrow too.


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## Beirdo (Jun 22, 2012)

Oh, forgot to post earlier... The new batch of stannous made the expected zero difference to the color of the solution (on a QTip). I will be buying some bleach (ran out) on the way home, and will use that to drip in there as suggested. That would help dissolve the gold, is that the trick? After that, treat it the same as if I'd done HCl/Bleach processing, I would assume?

Anyways, thank you so much all for your input.


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## Geo (Jun 22, 2012)

if the purple is as it looks to be, metallic gold as a colloid, a small amount of hcl and bleach will put it back into solution. DO add enough hcl to overpower the tin that caused it in the first place.


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## Beirdo (Jun 23, 2012)

Thanks. I will definitely give that a shot. It's so beautiful, but I'd rather have the wee bit of gold back, thanks. Didn't get a chance to get bleach on the way home as my buddies at work (today was my last day at my old job, new one starts Monday) took me out drinking... But there's always the weekend!


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## tek4g63 (Jun 23, 2012)

Could the purple color be from something in the capacitors going into solution? I plan on trying my hand at some CPU's in the near future, fiber and ceramic ( separately of course). So thank you for posting this. It will give me an idea what to look out for.


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## samuel-a (Jun 23, 2012)

It's possible... but hrad to tell by the picture.
Capacitors do leave a purplish colloid when leached in HCl or AP. It takes a week or two to settle.

Let's see what Beirdo come up with ater the HCl+Cl treatment.


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## butcher (Jun 23, 2012)

I feel it has something to do with the acid you are using, the Kleen strip "Green" Muriatic acid with 90% less fumes, the MSDS tell very little about what this acid contains, as far as buffers or inhibitors or other ingredients, and the statement 9% to 36% Muriatic acid or something to that effect on the MSDS, along with these buffers may not be toxic, and not listed in the document, lead me to believe the acid is the source of what color your solution made.

It is possible you made some colloidal gold but the color and volume of solution, seems like an awful lot for using strait HCl, and I suspect unless something went totally south to put that much gold in solution the color is from some other cause.

Have you tried to filter this solution? Tin in chlorides does not filter worth a darn.

Can you try a side-by-side small experiment using the clean stripe brand Green HCl and normal HCl on some of the same material in a small batch to see the difference in reactions?

I may try something like:
Wet a cotton ball with some of your purple solution, put it in a test tube (or in spot plate cavity), add a dilute NaOH solution to the test tube (or spot plate cavity) and bring pH to neutral, push cotton ball down in test tube/plate cavity and let everything settle well, pipette out any salt water, heat to dry cotton ball, once dry, I would incinerate the cotton, maybe few drops of alcohol to get the fire burning, and re-dissolve the remains with a few drops of HCl /bleach, a little heat to drive off free chlorine and then use the stannous chloride test to determine if there was actually any gold involved.


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## lazersteve (Jun 23, 2012)

I've seen this several times when working surface mounted capacitors and HCl. I believe your seeing a nickel ion in solution. I confirmed nickel with DMG in basic solution several years back when I first saw this. 

I seem to remember that adding water (or more acid - can't recall which) pushed the color back to lime/blue-green the last time I ran some of the caps. I didn't see any mention of cobalt on the manufacturers specifications for similar caps.

Cobalt appears either dark blue (cobalt blue) or pink depending on the amount of water present as already stated above. It also smells so bad it nearly makes you want to vomit when highly concentrated.

Steve


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## Beirdo (Jun 23, 2012)

butcher: I'm specifically NOT using the one with 90% less fumes. I left that crap in the store. This was marked as straight muriatic acid, not "green" muriatic acid. I was very careful to take the non-green. And it most definitely fumes. My nose can attest to that, unfortunately. Got a wee snoot-full when I first opened the bottle, and a wee bit in the air since.

I can try the incineration, sure. The solution in that bottle is post-filtering (the filter paper was still in the funnel when I took the picture, in fact), so I think colloidal makes sense to me as it would make it through the filter papers.

OK, I'm off to Walgreen's (closest place open) to get some bleach and cotton balls and more QTips (since I've pretty much run out of those too!) I hope to have time to experiment this evening, and to post the picture of the foils that used to be capacitors. It's been a busy time with changing jobs, and doing sound for a wedding, etc.


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## Beirdo (Jun 23, 2012)

lazersteve said:


> I've seen this several times when working suface mounted capacitors and HCl. I believe your seeing a nickle ion in solution. I confirmed nickle with DMG in basic solution several years back when I first saw this.
> 
> I seem to remember that adding water (or more acid - can't recall which) pushed the color back to lime/blue-green the last time I ran some of the caps. I didn't see any mention of cobalt on the manufacturers specifications for similar caps.
> 
> ...



Ahh, now this could be too. Hmm. I wish I'd gotten around to ordering that DMG from the guy here on the forum (names elude me sometimes, I have you bookmarked on ebay).

If it were nickel, I guess I'd need to find a safe way to get it outta there, or just toss the solution entirely. Nickel salts are known for toxicity, are they not? Precipitate with Zn or Al perhaps? I do have both in powder form.


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## lazersteve (Jun 23, 2012)

From my experience with processing lots of surface mounted capacitors, I can confidently tell you it's nickel. To put your mind at ease get some DMG and test it.

As to why it appears purple, I believe it has to do with the nickel forming a compound with some of the other organic components of the capacitor substrate, or perhaps an interaction with other base metals in the same solution.

I've seen it many times, it always ended up being nickel, never gold. Some surface mounted caps do contain gold, but typically it is visible on the surface (and also sometimes inside) of the component when present.

Try two small samples of the purple solution: Dilute one with water and add muriatic acid to the other, one of the two should shift the color back to the familiar nickle lime-green color when the proper pH is reached.

Steve


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## Beirdo (Jun 24, 2012)

Ahh, I detect the voice of experience there.  That is a dead simple experiment to make too. It wouldn't surprise me one bit if it were nickel, actually. And if it were gold, I'm surprised that there'd be that much of it to get such a rich color. So yeah, nickel sounds reasonable for sure.

I realized as I walked back with my bleach... if I do try to precipitate with Al or Zn, I probably would be best off starting with a neutral solution, wouldn't I? Heh.


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## Beirdo (Jun 24, 2012)

OK, simple experiment done. I need some good chemical measuring devices like pipettes.. anyways, here's how it went.

I put about 1/4" of the solution into two 175ml pyrex (glass) ramequins. Then I added water nearly to full to one, slowly, and muriatic acid nearly to full to the other (also slowly). The one with water didn't change color (just a diluted version of the same hue). The one with more muriatic acid turned to a blue reminiscent of cobalt blue glass, but more dilute.

The one with water:



The one diluted with muriatic acid:



Also: here are the little metal flakes I was talking about in the wash bowl (with the silver/lead chloride still in there, haven't gotten to separating them yet). Note that they are exactly the size of the larger capacitors used on the bottom of the PIII processors, and that all of the rest of the capacitor is seemingly gone. I'm curious as to what metal they may be.




Finally: since someone did ask for a picture of the jug:






edited to fix the attachments.


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## Beirdo (Jun 24, 2012)

Conclusion: whoever said cobalt seems to be correct.

http://en.wikipedia.org/wiki/Cobalt(II)_chloride

The blue is anhydrous (as it's in strong HCl, I guess), the purple is Hexahydrate. The solution if concentrated is apparently red when cool, blue when hot. I obviously don't have a concentrated solution.


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## Beirdo (Jun 24, 2012)

Note, I will still be purchasing some DMG and will test it for nickel  Having more test solutions is a good thing.


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## butcher (Jun 24, 2012)

Beirdo, did you see where they make invisible ink from cobalt chloride, Hmm could you use this as a test to see if it is cobalt chloride (heating and cooling) to see color change in the ink.


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## Beirdo (Jun 24, 2012)

Yeah, I was thinking on that. If it is cobalt chloride, I have no real use for it (other than to look pretty) at this point, and it's considered toxic to the environment. Wonderful... Good thing I don't have much of it, really.


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## Beirdo (Jun 24, 2012)

Ah yes, the DMG was from Patnor. Order placed, along with the other two test solutions all at once... might as well. I think it's nice that we are able to buy stuff from people who we know a bit better than just the random bloke on ebay... which isn't much of a compliment with the way ebay runs things.


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## lazersteve (Jun 24, 2012)

I did some more google research last night on the manufacturing process of the MLCC and found that Cobalt is sometimes used a dopant in the manufacturing process for the capacitors. It is added to the substrate film to promote proper electrical properties to the substrate. 

I still stand by my orignal posts that Nickel is also present in greater quantities than Cobalt. I make this statement based up the fact that the contact electrodes contain nickel as a primary ingredient. When you get your DMG test it and you will find Nickel.

Regardless of what the metals are in your solution, I can assure you they are not gold. As a side note on the solution, be careful of Nickel and Cobalt solutions as they are poisonous. They can both cause skin rashes and Nickel is a carcinogen.

From the wiki article on Cobalt II Chloride you can dehydrate a sample and perform the flame test on the dry salt to confirm. A blue-green flame indicates Cobalt II Chloride 

Steve


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## Beirdo (Jun 24, 2012)

Yeah, understood. Neither nickel nor cobalt are metal salts that I wanna mess with. Maybe if I had glass maker friends I could look at making cobalt blue in limited quantities, but nope, so nope. But now I have some here, and I'll need to find a reasonable way to dispose of it, I guess.

I agree with your conclusion. Likely no gold (or extremely limited quantities) in that solution, and hardly worth worrying about other than disposal at this point. I still want to test it, as I expect there will still be nickel in there too. It's good to know what you're dealing with, even if you're just disposing of it.

As I have like 300g of MLCC in a container that I've pulled off boards, I'm sure this will happen again if I use HCl to drop off the solder from them, so learning along the way is still a valuable thing for me.


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