# Aesthetic Iodine/Iodide Precipitation



## solar_plasma (Mar 20, 2013)

*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:


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## NobleMetalWorks (Mar 20, 2013)

solar_plasma said:


> 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


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## solar_plasma (Mar 20, 2013)

> 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.


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## solar_plasma (Mar 21, 2013)

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.


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## solar_plasma (Mar 21, 2013)

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.*


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## ericrm (Mar 21, 2013)

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?


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## solar_plasma (Mar 22, 2013)

ericrm said:


> 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.


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## Marcel (Mar 22, 2013)

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...


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## solar_plasma (Mar 22, 2013)

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.


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## solar_plasma (Mar 22, 2013)

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


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## ericrm (Mar 22, 2013)

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


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## solar_plasma (Mar 22, 2013)

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


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## ericrm (Mar 22, 2013)

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


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## solar_plasma (Mar 22, 2013)

...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.


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## solar_plasma (Mar 22, 2013)

ericrm said:


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



destilled plain water


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## solar_plasma (Mar 22, 2013)

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


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## manorman (Mar 23, 2013)

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


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## solar_plasma (Mar 23, 2013)

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.


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## solar_plasma (Mar 23, 2013)

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.


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## solar_plasma (Mar 24, 2013)

I think that looks good until now.


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## solar_plasma (Mar 24, 2013)

0,7 g gold; from the purple precipitate, it got very dark when dried.

So, together with the cementated almost black powder 0,9 g. An unknown amount of later cementated precipitate is still filtering. The first half of it was brown (gold?), the last half of it is grey (palladium?)


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## solar_plasma (Mar 24, 2013)

clearly to see: a grey layer above brown stuff

the dried purple pricipitate has a high density (left), it's 0,7 g. The dark powder (from first cementation) on the right weights only 0,2 g!



81,8 g leached scrap left back. As you can see, it was mostly RAM's and comparable material.


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## solar_plasma (Mar 25, 2013)

3,7 g (above)
0,7 g (left)
0,2 g (right)
___________
4,6 g unrefined gold (I assume some palladium, because a part of the cementation made grey powder. I guess about 0,1g can still be scrubbed off the material and some 0,1 gramms will maybe be collected, when I've cleaned all vessels)


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## lazersteve (Mar 25, 2013)

Got any photos of the melted gold buttons and their final weights?


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## solar_plasma (Mar 25, 2013)

No,I want to refine the material first and that means reading, reading, reading  ...and understanding

BUT I have made a test with DMG on the grey powder, so this should be palladium, right?:


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## ericrm (Mar 25, 2013)

finger and such look indeed to be copper,did you look with an pen eraser, or scratching with a knife to make sure you are 100% positive that you have leached your gold and not only deposited a fine deposit of metal or iodine as on my computer it look pink/purple and spotted rather than a very pale pink from virgin copper. i should receive my iodine in about a week and experiment just like you...


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## solar_plasma (Mar 25, 2013)

The copper fingers look like freshly etched copper with some spots of cemented palladium. It's pure copper for sure.


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## lazersteve (Mar 25, 2013)

Solar,

Your photos are too distant from the test tube to be able to get a close up view of what is in the test tube. Get your camera closer to the test tube and set it to macro mode to take a closeup, detailed photo of what's in the bottom of the test tube like this one:








Steve


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## solar_plasma (Mar 25, 2013)

Thank you Steve for your sceptical questions. I retried and this time no yellow. Paradox. I incenerated a very smal piece in a tube till red glowing heat and purple fume occured, there is a copper-reddish spot in the middle now - the grey powder must have been some copperiodide?

Then I testet one black piece from my purple precipitate with a little torch, it didn't get hot enough to melt, but here occured nothing unexpected. I retry later by autogenous welder, when I have time again.

I know, I have to be sure before I go on. I will find out.

Thanks.


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## solar_plasma (Mar 25, 2013)

I've heated some very small pieces with oxygene and it melted. It's a silver white metal!!! ....any ideas so far? ....and it is magnetic!  wow,I have made nickel metal? :roll: maybe 2% nickel alloy and I have found the 2% ultra pure...nickel? :roll:


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## solar_plasma (Mar 25, 2013)

Mistake 1: I've heated some grey powder, assumed Pd), I didn't know for sure, what it is (small amount, but neverthess, also small amount can cause diseases or explode)

Mistake 2: Since my SnCl2 seems not to work,I have not tested the black/purple material, assumed gold, for gold ...that was stupid.

I think two mistakes are enough to learn of on one day.

I will first go on, when I could test positive for gold. Then I want to wash the material first with clean KI to get all iodides washed out, then with hot water, then like Harold V. advices with inceneration and washing with acids before melting. I have to read this point again and I will ask, if there is something I don't understand.

Lesson learned today: Never think you are smart!


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## lazersteve (Mar 25, 2013)

Be careful incinerating compounds containing iodine, the thick purple iodine vapors are poisonous. Iodine will also stain (red to yellow brown stains) just about everything it comes into contact with that is organic. It's best to heat iodine compounds in a closed system with a cold finger condenser to trap the iodine via sublimation as the iodine vaporizes upon decomposition.

Steve


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## solar_plasma (Mar 26, 2013)

Yes,that's a good advice, since I can not be sure to be able to leach all iodides out with the KI-solution and thereafter with water. I thought of bubbling the fumes through sodium thiosulfate at the end of the assembly and to lead an inert gas through the vessel with the stuff that is to be incenerated, so the fumes will be borne through the assembly. What would be inert? with glowing base metals they could react, though...or bad idea at all? I have no Helium, that would be nice.

Edit: since I have no helium, I will not send any gas through it. I'll build a condenser and for safety thiosulfate at the end. Then I can reuse the gained sublimate for a new Lugol's solution.


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## solar_plasma (Mar 31, 2013)

For all those who followed this thread and who are as new to iodine as me: I think iodine is getting interesting at a point, at which I hardly would do experiments and learn just by reading (look: http://goldrefiningforum.com/~goldrefi/phpBB3/viewtopic.php?f=34&t=4301&start=40)

I consider the NH4I-method to be highly dangerous, if you not EXACTLY know what, how and when to do! Well, nothing I will "try out" by a recipe. I wished, some of the iodine-experts would live nearby. NH4I seems to do, what I had hoped KI/I could provide.


...and hey,the chlorox-method is lovely! Very nice to controll. Since today I guess I have a new favorite! :lol:


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## solar_plasma (Apr 2, 2013)

I've ordered an* ORP-electrode* for my pH/temp/I/U-multimeter, now. I have not given up, so far! 8)


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## ericrm (May 17, 2013)

so i just started to play with iodine this week and here are the result


i used high purity i and ki and demineralised water 1/ 4/ 10 by weight

the etching rate is indeed fast 
but it cemented back on the item...
i dont have the picture but i have leached finger with iodine and disolved the "aparently non gold bering finger) in ar the result "seem to be" a positive for gold.... 
and i did got a lot of with yelow and purple unknow precipitate...

i have a question for those who knows better than me, am i trying to make gold iodide or gold potassium iodide?

i will try more in the next week but for now like stuk like everyone else...


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## ericrm (May 17, 2013)

i just made a second try with 6g I/ 26g KI/ 176g h2o and the result are worst... on a little " plated bracelet" the solution seemed to attack base metal faster than gold and let gold in flake when i was shaking it.it also make a lot of whitish precipitate...

i tryed with a finger from memory and all it did was to cover the finger with a dark residu, i have removed it with a paper towel ,and it is blue.. i suspect that iodine plated on the gold...

i dont know what im missing ...

the white stuff seem to apear on contact with copper/ base metal under the nickel layer...

edit ... it is copper(i) iodide thank you wiki


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## solar_plasma (May 18, 2013)

> gold iodide or gold potassium iodide?



I read only about gold iodide AuI3 (edit: no, I meaned AuI). KI is only present in order to make the iodine solvable, as far as I understand. Could any chemist or hydrometallurgist say something to this?


In the summer vacation iodine will be one of my projects again, this time with ORP-meter. I guess without, you have no chance and, like me, end up with a copper, cobalt or nickel button. I do not expect the great success. Until now, I am come to the believe that the selectivity is widely overestimated or at least only benefits in special settings like ores and/or big leaching units.

Is there anybody who used this really succesful on small-batched e-scrap? And if, - how did you do it?

I wonder, if the cementation could be avoided by a steady flow of fresh leaching solution. Then the solution, that "filtrated" through the pins e.g. could be separated from the gold by for example electrolysis (if it was only iodine solution without KI) or resin. The solution would have to be regenerated and would newly flow through the gold plated material. But again, this would probably only work in a big well-controlled unit.


But what is wondering me mostly, is the fact, that no paper tells anything about the cementation problem!


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## solar_plasma (Oct 11, 2013)

*Back to the reason of my sleepless nights:*

I believe precipitation of gold III hydroxide will be a way to go. Gold III hydroxide, formed from gold I iodide by adding NaOH or KOH, which leaves NaI or KI in solution, forms oxide when dried, which decomposes at only 160°C to its elements. Most possible basemetals will form hydroxides too, which mostly will be soluble in acids, others allmost insoluble in acids. So, they should be easily removable before further treatment of the gold. So, decanting solution from hydroxides, rest gets vakuum filtered, NaI respectivly KI re-uses by oxidation of iodide to iodine. Hydroxides are heated to 200°C and get acid washed thereafter. Gold remains in the solids together with acid resistant compounds 

Comments are welcome. Otherwise I crack that nut alone, if I have to! *dreaming* then aaaaall the honour is mine undevided  ...no, any helping on the right track is very welcome! Ti-i-i-ime is on my side. 8) :lol: 

*Btw: To all other newbs: this is an alternative recovery method, which I am trying to understand and learn. I think it contains unnecessarily many steps compared to the usual methods. It is nasty. It is poorly described on the net. There are good reasons, why AP, AC, AR and sulfuric are the common methods *


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## ericrm (Oct 11, 2013)

solar_plasma, how will you deal with your copper iodide waste?


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## solar_plasma (Oct 12, 2013)

Since it was only a small amount of dark cemented material, I had heated it in a test tube, catched most of the iodine vapours in some potassium iodide solution in two erlenmeyer flasks. The decomposed, maybe glodcontaining, black powders I added to some incinerated filters and other small black gold recoverings. Removed basemetals,dissolved in AC.


But copper I iodide should be white. I had not seen any white insoluble material. It may have been dirty in the grey materialde scribed above,which came from "cementation" on copper. BUT there is no need for cementation, if we only go after the hydroxides.

In water copper I iodide is quite insoluable, so maybe it is more soluble in other conditions or it is left in the leached material which should not make any headache, as long as gold I iodide is soluble in the leach.

Next time I would treat the leach, when it is still brown. Then adding NaOH or KOH and seperating the formed hydroxides, noting their respective precipitation pH and their colour. I just need to know the range for gold III hydroxide precipitation, which first have to try on a gold standard solution.

Btw measuring ORP and pH under the leaching seems critical after what I read.


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## solar_plasma (Oct 25, 2013)

I have tried iodine/iodide on samples of pure copper, pure zinc (both at pH over 7(made me wonder)) and a heavily plated sugar spoon, which contains 1,6g silver (plating mark "100" = 100g/2400cm2 (pH by accident 1,5, adjusted with HCl, - there are different informations, but it should be higher)

copper: leach discolorized, white pricipitate of CuI, the excess copper is not tarnished
zinc: leach discolorized, white pricipitate of ZnI2, the excess zinc is still greyish
silver: the leach was in excess, still brown after 2h, no pricipitate after 2 h, spoon got white tarnish, - when I rubbed some white tarnish off with glass wool, the wool got yellow

combined from english and german wiki (some of the solvents are very dangerous and nothing for the hobbyist):


> *CuI: *
> white
> solubility: 80mg/L 18C H2O
> soluble in ammonia and potassium solutions
> ...


edited 25.10.2013, 21:27, source: Römpp Chemielexikon, 10th edition

I am very excited to see the spoon next monday.


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## solar_plasma (Oct 25, 2013)

Next experiments will take care of ORP and pH and elaborate the effect on the selectivity of the leach.

They say ORP should be kept at 450-475mV
https://www.google.com/url?q=http:/...ds-cse&usg=AFQjCNHjQwaoUH2-N4W1cKMN0SLRfnlKWQ

or at 400-900mV
https://www.google.com/url?q=http:/...ds-cse&usg=AFQjCNEDBGV6Ns5XUj3Jf4JlY-VSnGE7aQ

the pH at 2
https://www.google.com/url?q=http:/...ds-cse&usg=AFQjCNF9sEuQelhZSr3oPiVfK0NrJNHPDA

pH at 4,5
https://www.google.com/url?q=http:/...ds-cse&usg=AFQjCNHBo6DNzjO5PAfqs9f3foil6uiZTA

there is also mentioned pH 1-6,5
https://www.google.com/url?q=http:/...ds-cse&usg=AFQjCNH8V6dstxuiv14sCtfdVqc479CPpg

the leaching will stop when rising over pH7
https://www.google.com/url?q=http:/...ds-cse&usg=AFQjCNE_YcHhZUELDzzW9R2vTZYIIYX_MQ
If there are differences in the pH&ORP setting regarding the type of leach (only iodine or iodine/iodide) and regarding the leached material, is another point which has to be clarified.


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## solar_plasma (Oct 28, 2013)

Left:
The silver plated spoon in iodine/iodide/HCl/pH1,5 (at the beginning) developed a thick,unsoluble, yellow crust of silver iodide, which comes mostly easily down. The basemetals beneath do not look attacked.

Next challenge will be to find the best method to get the silver out of this compound without losing the iodine, which has to be reused, if this method should make sense.

I hope I can oxidize 2I- to I20 and at the same time form a soluble compound of the Ag+. So, I have to find out and reread all documents, if HNO3/H2O2 can be used as the oxidizer.

Middle:
Zinc iodide is soluble and leaves a colourless clear liquid. pH over 7,5 at the beginning

Right:
Copper iodide is also somewhat soluble, but here we got a white precipitate of copper iodide,too. pH over 7,5 at the beginning


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## solar_plasma (Oct 28, 2013)

> Next challenge will be to find the best method to get the silver out of this compound without losing the iodine, which has to be reused, if this method should make sense.



And here is the answer, - I knew I already had read about it 8) . I'm sorry it's in german, but the equations are international:
http://www.chf.de/eduthek/wuchu/1996_3.pdf


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## jonn (Aug 7, 2014)

Hi Solar, I'd be interested to know if you ever had any success with this process.


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## solar_plasma (Aug 7, 2014)

I have got 1,5g silver from this spoon the iodine way. But is has no advantages. From all methods I tried on silver plating the H2O cell had most advantages.

Regarding gold, I would also say, no advantages, but a lot of disadvantages, especially since you never really know, where your gold is and you never get all iodine back.


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