AP -> HCl/Cl -> wrong color AuCl?

[chlaurite]

So I followed LaserSteve's videos step-by-step for processing some RAM and PCI fingers. First part (AP) worked beautifully, and I ended up with 1.3g of nice clean foils (probably a slightly high number, I didn't specifically heat them to drive off any dampness).

On to step 2. Put the foils in a graduated cylinder, added 250ml of 10M HCl, stirred it a bit to "wet" the foils that floated to the top, then slowly added 60ml of Clorox while stirring gently. It evolved a good bit of Cl gas for a few seconds (I expected that), and then everything looked great - It started turning a beautiful golden color almost instantly.

After a six minutes, everything had dissolved... Except the color had changed to the loveliest (but very very wrong) shade of green:
I let it sit overnight hoping the color just came from free Cl, but it didn't change noticeably.

So any thoughts as to what I did wrong, and how I can salvage this? I'll leave it alone it until I get some feedback, but I have two main thoughts. First, brilliant greens usually mean copper, but shouldn't that all have dissolved into the AP? And second, could I still have free chlorine causing that color, and if so, how can I best eliminate it?

Thanks!

 

[Geo]

did you test with stannous? it looks like its contaminated with copper. it really depends on your expectations. i have had dissolution's that was much more contaminated than that.

 

[goldsilverpro]

Blue plus yellow equals green. Dark green plus yellow equals lighter green. Dissolve copper and gold together and it will likely be green.

 

[mls26cwru]

So I followed LaserSteve's videos step-by-step for processing some RAM and PCI fingers. First part (AP) worked beautifully, and I ended up with 1.3g of nice clean foils (probably a slightly high number, I didn't specifically heat them to drive off any dampness).

On to step 2. Put the foils in a graduated cylinder, added 250ml of 10M HCl, stirred it a bit to "wet" the foils that floated to the top, then slowly added 60ml of Clorox while stirring gently. It evolved a good bit of Cl gas for a few seconds (I expected that), and then everything looked great - It started turning a beautiful golden color almost instantly.


Thanks!

between harvesting the foils and dissolving them, there should be a number of rinsing steps... this is to get rid of the copper 1&2 chloride. The etchant used in the prossess can hold a surprisingly large amount of copper in it, so a small amount of etchant left over from harvesting can cause a large contamination. A series of HCl washes*** will help get rid of the majority of this left over stuff.

Mike

*** - you might need a series of HCl and water washes... can someone correct me if this is wrong/right.

 

[Geo]

washes will most definitely help. roasting the foils will also help followed by a boil in hcl. give the foils water rinses after that until the rinse stays clear.

 

[chlaurite]

Hmm, I did rinse them pretty well in (room temperature) HCl and then water, but didn't go so far as to boil them in HCl.

FWIW, the stannous test shows positive for gold, though weakly (a sort of pale purple, but I should mention that I don't see color so well). I think (as far as the stannous color goes) I probably just have too much liquid (by around a factor of 10) for the amount of foils I had.

So I suppose we have a viable hypothesis for where the (presumably) copper came from - Any suggestions on how to salvage this? At the very worst, I should still have the gold content of my original foils in that green solution, right?

I've searched the forum all day for people having even vaguely similar problems, and the standard answer seems like "cement it out on copper bus-bar". I wonder if got it that bad, though, or if I could perhaps still just drop the gold with SMB, then boil it in HCl, then re-dissolve it with HCl/Cl it for a second try?

Thanks for the feedback so far, guys!

 

[Geo]

i can understand where this seems to be a difficult thing to do and for someone that has never done it before it can be a daunting task. if you should happen to read Ms. C.M. Hoke's book "Refining Precious Metal Waste", it wouldnt seem like such a big mystery. retrieving precious metal from mixed metal salts is what refining really is. you want to know how to get your gold back from the solution you have. lets take a look at what we know.
1. you had gold foils from an AP process.
2. you dissolved these foils and the solution turned green. you cant understand why its green and want to know if you can retrieve the gold from this green solution.
3. you used more chemicals than was needed for the amount of material you had.
(*)please read Ms. Hoke's book.
(1.) you didnt prepare your material in a way to assure the outcome you were expecting.
(2.)AuCl is not green.yes you can retrieve the gold.there are a couple of metals that are green in solution. (Ms. Hoke's book gets you acquainted with dealing with base metals)
(3.)sometimes less is more.

evaporate the solution you have to about 1/4 of the volume you have now and let cool. retest with stannous. precipitate with SMB as you would a clean solution.
good luck.

 

[Harold_V]

Needless to say, I heartily endorse the admonition to read Hoke's book. Virtually all of the commonly asked questions would not be asked if readers would simply follow that advice. Further, they'd avoid irritating the hell out of me, as it's perfectly clear that many refuse to do so, so they waste the time of readers, hoping to be spoon fed the information they seek, instead of trying to better themselves. That's foreign to me, as I tend to do my own investigating.

No need to evaporate the solution. Gold, unlike the platinum metals, will precipitate perfectly well from dilute solutions. It is commonly accepted that it will be recovered to the point where there is no showing with a test with stannous chloride, which will report miniscule traces. The only real benefit of evaporating would be the test prior to precipitation would be more distinct. In this instance, I can't see that would be a benefit.

The lesson that should be learned from this is that base metals should be fully eliminated before dissolving the values. It isn't a bad idea to incinerate the resulting foils, then to give a boil in HCl, followed by a serious rinse, until the rinse water is clear. That should yield a golden solution that filters without issues.

There is nothing wrong with extracting values from dirty solutions. Just be prepared to do some serious washing, and to invest in a second refining. There will be times when you will dissolve values along with garbage (filings from the jeweler's bench are a good example). Just come to terms with the idea that dirty solutions will yield gold of lesser quality, if, for no other reason, mechanical drag-down.

Harold

 

[artart47]

H!
I had he same experience when I first started doing fingers. I just figured that the AP leeched enough copper from under the foils to release them from the board but, they weren't left in the solution long enough to completely remove copper that was still on the backs of the foils; also I figured some of the foils were per-haps alloyed and weren't pure gold. (never tested to verify either, just what I speculated back then)
So, I began collecting all the foils that I APed and storing them in a jar of HCl till I was ready to disolve them. I would shake the jar every day.
after a week or so at room temp, the acid would look like your solution. (the suggested HCl boil will speed it up) I'd decant the liquid and add fresh, after a time or two, it would be clear and colorless. The resulting gold was very high quality.
Harold gave you the best advise about understanding Hoke's methods and not disolving the gold till all the base metals are removed.
You can drop the gold from the dirty solution but,you'll have dirty gold that will need further cleaning.
Good luck!
artart47

 

[Geo]

thank you Harold for clarifying. the reason i advised evaporation is because he wasnt sure about the first test. evaporating dilute solutions gives a more defined result.

 

[chlaurite]

if you should happen to read Ms. C.M. Hoke's book "Refining Precious Metal Waste", it wouldnt seem like such a big mystery.

I must have missed that in my first full read-through of Hoke, as well as in a scan of the index just now. Can you point me to the page where she mentions proper cleanup of foils subsequent to using the AP method of refining gold scrap and before the HCl/Cl repurification step? :wink:

I sincerely thank you all for your feedback as to where I went wrong. I made a stupid, simple mistake. But do we really wonder why newbies get frustrated at repeated admonitions to read a book that doesn't even mention the single most common technique we discuss (for gold) around here? I already have "book-knowledge" of the chemical systems involved; I readily admit that I lack experiential knowledge of them, however. No amount of re-reading Hoke (or any other book) will remedy that - Only actual experience can do that, and that takes actually doing, and learning from our mistakes... Though, friendly guidance from those who do have experience can cut the time and number of mistakes drastically.

/ Next time, I'll know better.

 

[Harold_V]

While I agree that experience is the best teacher, and I'll acknowledge that in Hoke's book, there is NO mention of treating foils (they were unknown at that point in time), the basic theory is discussed. I will suggest to you that processing foils is much the same as processing gold filled, however. If you read the book enough times (I keep telling readers to read it until it MAKES SENSE), you'd have been able to make the determination of why you were experiencing your particular anomaly.

Try to keep in mind, Hoke prepares the reader for dealing with refining and understanding the expected reactions. Until you understand all she teaches, you'll have questions. So then, based on my theory, the one I formulated by reading Hoke until I understood refining, read Hoke's book. Read it again. Read it until you understand what she teaches.

Harold

 

[Geo]

chlaurite, you must forgive me for assuming that you didnt read Ms. Hoke's book. at first when you couldnt understand why your gold chloride was green and then again when you didnt know whether or not you could retrieve your gold from this contaminated solution or how to do so, well lets just say i was skeptical.

even though the book was written before modern electronics, the principles taught still apply no matter what material you are working with. i think a second and maybe a third reading may help you out.

 

[chlaurite]

First, I apologize, that post came out more snarky than I meant it.

Second, I agree completely, I will get more out of a second, and third (and more!) reading of Hoke - eventually. But I don't think that would happen just by reading it over and over in one go, but rather, by re-reading it once I have a good "real world" grasp of the parts that made sense to me on the previous reading and have made a few of my own mistakes in the meantime. The parable of the seed-sower comes to mind - Until my head becomes "good soil" with enough background experience to move forward, any seed sown there will fail to take root and grow.

So anyway, thanks for the advice, and thanks for having patience with me. Someday I hope I can actually give back to this community; until then, I'll do my best not to annoy (though I have no doubt I'll eventually have more stupid questions).

 

[lazersteve]

chlaurite,

You have carried copper I chloride over as the solid salt into your refining stage due to improper washing of the recovered foils. You can avoid the problem you encountered by doing a through HCl wash of the foils prior to the refining dissolution. Copper I chloride appears when your AP saturates and will no longer hold anymore copper, adding water (via the spray bottle) to the saturated solution increases this effect. The copper precipitates as yellow to light gray copper I chloride when water is added. Wash your newly recovered foils with HCl until the acid no longer changes color (first dark black/brown, then light yellow, then nearly clear when completed) and you should get yellow gold chloride solutions every time in your refining stage.

Steve

 

[butcher]

Hokes book has a tremendous amount of information in the book, the first time you read it, you learn a few things, but the book covers so much information you will not understand it all, reading it again and doing the getting acquainted experiments in the book gives you hands on with the reactions of metals and the acids, doing and seeing the reactions teaches you what to expect with different metals and acids, it also helps you to understand the metals which are troublesome, these experiments can give you tools in your tool box for troubleshooting problems or the tools to keep out of causing these problems in the first place, even after reading her book the second time, you may still not see the principles she is teaching in this book, it is a concept the book covers as a whole, this concept is actually fairly simple, but it is not written in words on the pages, every time I read in Hokes I learn more.

I have been reading, and re-reading Hokes book since 2008 and I still learn more every time I read in these pages.


The forum is like Hokes book, there is so much information, am always learning something new, I can read posts I read years ago, and learn something new, by read them now after I have more understanding than I did when I read them years ago.

As we gain a little hands on experience rereading Hokes or the forum also helps us to understand more, we begin to see small details we missed or did not understand when reading the first time, many times when we read we miss small important details, or steps are overlooked, maybe one word or sentence on a page, that may seem unimportant when reading something for the first time or two, but in recovery and refining missing a small detail or step can make a big difference in the end.

Harold gives very good advice when he harps to members over and over:
Read Hoke's book.
Read it again.
Read it until you understand what she teaches.

Then if we keep reading Hoke’s book we will keep learning more every time we read it.