Aesthetic Iodine/Iodide Precipitation

[solar_plasma]

EDIT: Since this thread is about my first attempt to leach with iodine, don't take anything for given. This thread contains assumptions, which partly turned out to be wrong.


You can say,what you want, but this is the beautiest precipitation I ever saw:
EDIT: yes,beautiful, but only nickel I guess. To see the gold precipitation read on :lol:

 

[NobleMetalWorks]

You can say,what you want, but this is the beautiest precipitation I ever saw:

Did you keep your PH above 8 so as not to dissolve any base metals? If so, how did you do so?

Did you precipitate using Acetic acid? Is that what you are expressing in your title?

Did you increase the PH to about 12.5 to precipitate the gold out of solution? And if so, are you using a PH/ORP meter to insure you are fully precipitating and are able to control your PH?

Are you regenerating the Potassium Iodide/Iodine solution after gold is precipitated?

I am very interested in this process, it seems if it can be perfected, that this would be the safest and best way to remove gold plating from e-scrap considering that this same method is also used to etch electronics.

Scott

 

[solar_plasma]

Did you keep your PH above 8 so as not to dissolve any base metals? If so, how did you do so?

no,I took clean goldplated copper, ram etc., pH under 2, the copper remained black

Did you precipitate using Acetic acid? Is that what you are expressing in your title?

no,I meant aesthetic like immanent beauty

Did you increase the PH to about 12.5 to precipitate the gold out of solution? And if so, are you using a PH/ORP meter to insure you are fully precipitating and are able to control your PH?

yes and yes, pH-meter

Are you regenerating the Potassium Iodide/Iodine solution after gold is precipitated?

yap, but it's my first real attempt

I am very interested in this process, it seems if it can be perfected, that this would be the safest and best way to remove gold plating from e-scrap considering that this same method is also used to etch electronics.

and the most aesthetic one

In fact I don't know anything yet, the gold was dissolved, I got a green precipitate and a very clear solution that turned from yellow-green to colorless under precipitation. Only copper and gold,I2,KI and KOH used,so that green stuff could be gold, since copper iodide is black [EDIT: no, it's white or grey], I think, and gold iodide is yellow-green.

 

[solar_plasma]

thin gold foils look green, when the light shines through them, but I wonder about the green precipitation....shouldn't it be black, brown or yellow? As long as I'm not sure, I have to be cautious. Now,I will research, if it will be safe to incenerate and then refine with a more well known, well explained and proven method. Maybe I wait and probe some more times with the modified/advanced AR-method with clean gold. Critics and advices are as always welcome.

 

[solar_plasma]

I'm rinsing the pricipitate, now. The pricipitate shows pink reaction with DMG at alkaline pH but without NH4OH! Nickel in RAM-contacts? The remaining black coating on the contacts may be cementet gold. I believe, the tutorials, which I have used are too unprecise, since I think I've followed them to the point. If I once will find out, I will post a really usable tutorial for that process. I'll hold on.

Edit: Since I believe the gold still was cemented to the copper, I've leached again with a fresh solution. This time I didn't want let it be cemented back, so I remembered K Williams words: Keep it brown!
I kept it brown and it looks like making coffee in a beaker: A obviously dark precipitate already at pH 6.22. That matches to the most sources, which say, gold would precipitate at 6-7.

Btw. the copper contacts are grey or white - copperiodide,i guess. Now, the products seem to be plausible.

 

[ericrm]

your post is very interesting, i have read that iodine sublimate and give a caracteristic odor. how does it smell ? is it s strong odor?

 

[solar_plasma]

your post is very interesting, i have read that iodine sublimate and give a caracteristic odor. how does it smell ? is it s strong odor?

Like in hospital it smells. Be carefull, it can make chronic diseases after long term exposition.

So, I have to declare that after all reading, experiments et al. the tutorials I had used are useless (combined with the individual background I own and the type of scrap I processed). The different tutorials are in my eyes completely paradox. They lack reaction formulas and precise description of what happens and why. No description tells, that there also will be formed iodates. I can only give advice not to waste time with it, unless you have somebody, who uses this method with succes and who will lead you.
I have none.

For me, it was only an experiment to see, if I could make a good schoolexperiment out of it. The gold was secondary goal, since other methods like AR worked for me at first attempt.

I consider to clean up by making pH under 6 again (works), extract the pure iodine by traditional methods and cement the values or cement directly from brown solution, processing/recycling the iodine later for re-use in traditional school experiments.

 

[Marcel]

So can we finally add this project to the long list of disappointing iodine tryouts ?
The hardest part is still to come. Try to get the gold out...

 

[solar_plasma]

As a school experiment so far: YES
Nevertheless I will READ every new post about it and all material I will find in the long term, because it is interesting. Before I try it again, I would prefere to know very much more about it's chemistry,than I could find until now. What a pity Hoke didn't write about it. Did Hoke know the method?

Getting the gold out (according to your book it should be 2-4 g) will be interesting, indeed. I will love to share my experiences if it is desired. Until now it looks good.

 

[solar_plasma]

The copper in both vessels went black and some hours after there was precipitate to see:

 

[ericrm]

can you tell us what iodine mix you started? ratio ? potassion iodine ,sodium iodine, lugols premix, something else?

 

[solar_plasma]

At first 1,3% iodine/ 15% KI, then I made it by myself: 7,5%iodine/15% KI, further I used pottassium hydroxide 10% for raising pH

for lowering pH in order to dissolve the precipitates and before cementing/saving values: HCl 33%

cementing: Cu

at all time I had sodium thiosulfate for a case of emergency to bind iodine and to decontaminate vessels

 

[ericrm]

1.3% i ,15% ki the rest was plain water?

 

[solar_plasma]

...and since there obviously are many who feel attracted by iodine-leaching: Use only gold without any basemetals for the first attempts. That's a good idea when learning the other methods, but here it's finally more important, if this could be the case at all. And don't start with it, if you don't have a solid background to foresee, identify, handle unexpected reactions and to clean up. You will need it.

 

[solar_plasma]

1.3% i ,15% ki the rest was plain water?

destilled plain water

 

[solar_plasma]

I am filtering, now. The filtrate is colorless. It may only contain K+, Cu+, -I and maybe smaller amounts -IO3. I wonder, if the Cu+ could be precipitated with pottassium sulfide, but the -IO3 should maybe first be reduced to -I by glowing with C. Then there would be only KI left after dissolving in H2O and filtering. Then maybe crystallizing it out with some K2CO3.... I have to remember to try this once with clean definated solutions.

Btw.: remember not to put sodium thiosulfat into HCl, since it will form SO2, unless you want SO2 / don't use NH4OH combined with iodine or its compounds without deep research since it could form explosive products

 

[manorman]

For Fun you can let a small amount of your filtrate evaporate on glass and see if you get you Gold Mirror, if you have gold in the soluton it should work.
I got that result on a number of ocasions.
Mike

 

[solar_plasma]

The last thing I want to do is to evaporate my gold! :lol:

Now, after I've read another abstract, which says "at least pH 12,5",I think one problem was,that I had a pH-meter. If I hadn't, than I would surely have added enough KOH to raise pH far over the 12,5 and gold would have precipitated.

I've dried 0,2g (obviously) gold from 1/2 of my solutions. The ram-fingers are black, so maybe the at least expected 2g gold still linger cemented to the remained copper.

 

[solar_plasma]

I used plenty of KOH, since the pH seemes to be buffered around 12-12,5. I have raised it to pH 12,7 First the solution got purple, then darkened and finally I got a purple pricipitate - should that have been it? Purple like colloidal gold? We will see.

Edit: Yessss, that's it! Super fine purple gold, half of it passes the filter directly, staying long time in the liquid, then sinking more than slow to the ground. Decanting may be much better, than filtering.

Edit2: Once dried and weighted, I will try to dissolve a small amount in some drops AR, dilute and make a SnCl2-test.

 

[solar_plasma]

I think that looks good until now.