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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!
 
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.
 
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.
 
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.
 
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
 
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.
 
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.

Cobalt appears either dark blue (cobalt blue) or pink.

Steve
Click to expand...

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.
 
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
 
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.
 
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:
IMG_0233.JPG

The one diluted with muriatic acid:
IMG_0234.JPG

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.

IMG_0235 (1).JPG

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

IMG_0238.JPG
IMG_0239.JPG

edited to fix the attachments.
 
Note, I will still be purchasing some DMG and will test it for nickel :) Having more test solutions is a good thing.
 
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.
 
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.
 
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.
 
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
 
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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