After SMB only fine white heavy residue

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Snowdog

New member
Joined
Jan 27, 2013
Messages
4
Hi

I am a nubbie at this and need a bit of help please.

I had about 20 DIMMs and a couple of cell phone pcb boards and covered with hcl in a beaker on hot plate.

Added small amounts of Nitric Acid until gold was gone.

This left a very dark green solution.

I cooled then filtered the solution and added Sodium bisulphate to precipitate the gold.

I left the solution for 20 hours and tested using Stannous Chloride (I wasn't sure how to make up the Stannous powder so I mixed 50/50 with water) This did not change colour it stayed clear.

I assumed all gold had been precipitated but when I poured off the liquid there was only a kind of heavy white material hanging in the solution at the bottom.

All the gold has gone from the pcb boards so I assume the gold is still in the solution.

Any ideas as to where I went wrong and what I can do?

Thanks
Rich
 
I had about 20 DIMMs and a couple of cell phone pcb boards and covered with hcl in a beaker on hot plate.
You mixed all kinds of metals, oils, and trash together even one of the worst TIN.

Added small amounts of Nitric Acid until gold was gone.
Now you put gold into solution with this mess.

This left a very dark green solution.
Trash dissolved in solution with gold forming a mess of colloidal gold

I cooled then filtered the solution and added Sodium bisulphate to precipitate the gold.
You added the wrong chemical here making a mess a bigger mess, it would not have done any good at this point, but i did not see where you removed excess HNO3 first.

I left the solution for 20 hours and tested using Stannous Chloride (I wasn't sure how to make up the Stannous powder so I mixed 50/50 with water) This did not change color it stayed clear.
This does not surprise me you have free HNO3, and or gold reduced by tin, (you had stannous chloride in your first step when you put a circuit board with solder into the HCl, what do you expect your test will do at this stage? reduce the already reduced gold?)

I assumed all gold had been precipitated but when I poured off the liquid there was only a kind of heavy white material hanging in the solution at the bottom.
Trash in and that is what I would expect trash out.

All the gold has gone from the pcb boards so I assume the gold is still in the solution.
Yes but it will be terribly hard to get it back now from this mess.

Any ideas as to where I went wrong and what I can do?

I just have one idea study and look and see what is out that airplane door before you jump, also make sure you have learned to wear a parachute.

First stop messing with these dangerous chemicals you know nothing about, stop before you hurt yourself or others.

Put up your solution and chemicals up in a safe place until, you have studied enough to get a good understanding of what to do and how to do it safely.

Do not keep loosing your gold, but spend the time needed to learn to recover and refine your gold.

Study Hokes book, and the forum.
Study the safety thread and dealing with waste.
Read the guide to the forum.
Collect scrap while you study.
After you have read Hoke book all the way through once, start reading it again, this time performing the getting acquainted experiments in Her book, as you do these come back here and read this post, see all of the mistakes you made here, and after you have done the experiments and have learned what Hokes teaches, you will then know how to get gold out of this mess, you will know how to recover gold and valuable metals without making such a mess, and you will also have an understanding of how to refine those recovered values.

This is your best bet for not losing your gold from making costly dangerous mistakes, and will be the fastest way for you to learn and be able to get up to speed melting your pure gold buttons, not taking this advise you can struggle along for a long time losing gold and making messes, and putting yourself and others in danger.
 
Hi butcher

Thanks very much for taking the time to reply. Rest assured I have read the safety guidance and treating the chemicals involved with up-most respect.

I will take your advice and read Hokes book again more thoroughly and your comment about throwing everything in not being a good idea makes a lot of sense too. I did think that was a bad idea after I had done it.

One question before I start reading, do you think it is worth holding on to the solution I have, so when I have got my head around this a bit more I can get something from it?

When you say I added the wrong chemical should I have used Sodium MetaBisulfite not Sodium Bisulfate?

Appreciate your time. No more questions until I have researched.

Many Thanks
Rich
 
Reading the Guided Tour will answer the questions about chemicals and how to make stannous. The white stuff is likely a mix of many different compounds.

The Reaction List in the Guided Tour covers all of the common reagents and how to make them. Take the time to read and understand all of the links in the Guided Tour before you go any further.

Steve
 
Yes sodium bisulfite or sodium metabisulfite will precipitate gold, they form sulfur dioxide gas in solution with the acid this gas is what precipitates the gold, sodium sulfate, sodium bisulfate, or sodium metabisulfate will not precipitate the gold from solution, I did not know if you used the wrong chemical or just the wrong name for the chemical.

Yes you can recover the values from the solution, after you get a better understanding.

Follow Laser Steve's advice he is a great teacher.
 
That's good news, production has ceased! Thanks for the advise, I will keep the current solution.

Thanks both.
Rich
 
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