Gold precipitation issue with HCL bleach solution

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New member
Sep 24, 2018
Hallo everyone!
My name is Elia, I’m new in this beautiful forum!
I’m not a chemist and wanted to ask some advises and possible solutions…
( this is my first message, hope to be on the right section, I haven’t done any presentation of myself but there is not much to say :) ...and sorry for some english errors, is not my native lenguage )

I’m processing some electronic waste (first time) and up to now I have been educating myself reading, studing and getting as much info as possible from internet. I’m a technical person with a basic scientific formation and usually I never do things before a deep studing of the matter but this time I’ve reached a point where I really need help from a chemist or someone with experience .

So little story : (I’ll try to be short but I will miss some points)
My electronic waste is made of everything, starting from connectors to boards, pins, ICS, etc...What I did was to start putting everithing in a beaker and add HCL, than put on the hot plate on medium and add some hydrogen peroxyde 3 % when hot to start scrapping all base metals...
I know I should did divede connectors from board etc.., but I took it as an experiment, my thought was to remove all the base metals with several washes of HCL and Hydrogen peroxide and remain with all the solid non metallic stuff, and the gold of course.
I did’t want to lost anything so I got all the filters in a jar, the waste acid on the stock pot with copper, second pot with the iron...I think I no need to explain this part...I’m trying to provide as much info as I can....

The point is this, when I was filtering some connectors I end up with a clean filter with some gold foils in it and nothing else, so I made the decision to process separately this small batch, just to see how it goes ...
( you know, I’m like a kids, I can wait :evil: )
Also wanted to answer to one of my question: does HCL and hydrogen peroxyde dissolve the gold ? Yes it does on the proper condition.
I did put just the little foils in a brand new 600ml beaker and a small piece of broken gold chain ( probably 750/1000) that I had around ( 0.14 grams).
I did want to refine this small gold quantity before “ the big “ batch to get practice. I than add 100ml 33% HCL put the beaker on the hot plate, set on medium and add probably 25 ml of 3% hydrogen peroxyde because I want to put in solution some residual copper...if it was...
Error 1 : I think way to much acid for so small quantity of gold
So what happen was that the gold foils start to dissolve and after a while also the chain ...this last one was than taking forever ( and became frizzing black, does this means that was probably just gold plated ? ) So I said to myself : ok I will add bleach to finish to dissolve all the gold. I added the bleach at small quantity, just enough to dissolve all the gold.( probably 15 ml ) When was all done I did left the solution on the plate to evaporate all the chlorine and some water up to 100 ml again...the solution was beautifully yellow/green , I would say like a yellow marker and crystal clear!
At this point I left the solution cool down up to about 30 *Celsius than I added 2 drops of drain cleaner ( solphoric acid 98% ) to precipitate any lead present...
Error 2: I didn’t wait for the solution to cool very well
Error 3: I think the drain cleaner contain some anti corrosive agent to protect metal pipes....
I than filtrate the solution and made it ready for precipitation on another clean beaker...up to here all good.
Than added 2 grams of potassium metabisulphate... after 5 minute nothing happen, then I ( stupidilly ) tought to add other 3 grams of it but than the first little tine brown powder grains was starting to form and than I don’t really know why I did decide to add other 5 grams for a total of 10 grams PMB.
Error 4: do I need to write it. :twisted:
Anyway the precipitation starts and than I left the solution overnight....the day after I was aspecting a like water color solution with the brown deposit on the bottom but instead was a very small amount of gold powder in the bottom mixed with a lot of crystalclear crystals even growing upward the beaker !! Some of the gold was gone back to solution and that one was green color and not at all like water....

So, big mess with the first probably half of a gram of gold, I need to know how to save the solution, if possible now to filter out the crystals and/or in some way remove all the PMB and start again...

For the other beaker that contains the most of the gold I think to bubble In some clhorine gas to directly put gold in solution and than filter all of it...?..?

Thank you so much to averyone that read my post up to the end and as you know, I made a lot of mistake, I need a lot of advises!

I can post some pictures if required to understand better but I want to ask what the best way at this days, it’s a long time that I don’t write in a forum...

Thank you! Many times !


Staff member
Jan 6, 2008
Pacific NW
Add a clean bar of copper to the solution, save it in a safe place, do not seal the container.

Study (some suggestions to get started)
Testing for gold in solution using stannous chloride or ferrous sulfate (either reagent you can make).
The General reaction list, the guide to the forum, and welcome members (general chat).
Dealing with waste, and situations to avoid (safety section).
Hoke's book, check the index for discussions of the stock pot in her book.

Ok, you have spent your time learning a few things that do not work, and more about what not to do, and how to make a big mess with toxic dangerous solutions.
If you are finished fooling around, then let's begin by learning how to clean this mess up, and begin fresh after gaining some of the basics needed to begin actually learning the skills of recovery and refining of precious metals.

Collect scrap while you study, learning how to separate scrap and mechanical processes, clean your scrap of organics and as much base metal as possible learn more about how the different recovery processes work, which processes for what types of materials, how to perform processes safely and how to deal with the toxic waste generated, basically gain some understanding before making your next mess.

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