# HAuCl4 with sodium sulfite



## Anonymous (Oct 25, 2010)

I appreciate anyone to help me with the other products - for HAuCl4 reacts with sodium sulfite besides precipitation of Au? -Ed Yu


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## butcher (Oct 26, 2010)

You may need to ask your question in another way, hard for me to understand what you are asking.

Sodium sulfite creates SO2 gas, which will precipitate gold from a solution of (pure) gold chloride, 

But if this solution of gold chloride had a lot of base metals dissolved in it then the sulfite can also precipitate the base metals along with the gold. 

And if really loaded with base metals the gold may not precipitate but may just plate out onto the colloidal salts dissolved floating in solution

There are several other chemicals that can precipitate gold from aqua regia

Hope this helps.


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## lazersteve (Oct 27, 2010)

SO2 will precipitate PGMs from non-chloride solutions also.

Steve


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## Lou (Oct 27, 2010)

Correct Steve. That's why sulfur dioxide precipitation is not advised when your solution is known to have palladium present. Palladium is an especially difficult metal to remove from gold using just SO2. Oxalic acid is usually the way to go when confronted with that situation.


Lou


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## philddreamer (Oct 27, 2010)

Do CPU's contain pd? 
Because after processing some CPU's & dropping the gold with SMB, I did a stannous test, it was neg for gold, but I had a medium lime green result. 
I added some clean copper to the solution a week ago & I have some brown sediment now.


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## Harold_V (Oct 28, 2010)

Can't help with the idea of is there or is there not palladium in a CPU, but if you ever have a question about the presence of palladium, a quick test with DMG will remove all doubt. It's very sensitive to even traces of palladium, and, as a bonus, you can also use it for testing for the presence of nickel. It's all in Hoke. 

Harold


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## Oz (Oct 28, 2010)

Harold's advice is spot on for detecting the presence of Pd. 

There is indeed Pd with some CPUs mainly (if not entirely) from the monolithic capacitors that reside on the chip. I am rather sure however that if you used SMB to precipitate, you removed the Pd with the gold as your sediment.

I am guessing that this is a chloride solution you precipitated. Gold and palladium will cement on copper as black from it. I would guess that you had a complete precipitation using SMB, but did not allow it to settle long enough before decanting/filtering/siphoning your solution if you are finding brown on the bottom.


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## philddreamer (Oct 28, 2010)

Thank you gentlemen!


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