Should i drop the Palladium first before the Gold?

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cytek

cytek

Active member
Joined
Oct 25, 2007
Messages
25
Location
Michigan
I just performed an experiment with 12 486' processors using AP. Washed several times with HCL then dissolved in HCL-CL. I tested the solution for GOLD with SC and i think there is a good amount of Palladium also. See below PIC>

Should i try to get the Palladium out first using ammonium chloride and sodium chlorate or should i perform the SMB drop for GOLD right now and then try drop the Palladium later, because i do not have ammonium chloride and sodium chlorate right now?

Cytek
 

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Here's my logic.

Gold can be washed extensively after precipitation. Palladium salt can not. It wants to re-dissolve. Gold first, then, if your solution contains enough palladium, evaporate the solution to concentrate, then attempt precipitation of palladium. Remember, it won't precipitate from a dilute solution-----don't skip the evaporation process.

You can also recover the values in your stock pot, accumulating enough to make processing worthwhile. You'll come to realize that that is the best strategy unless you have a lot of palladium.

When you precipitate gold, if the solution contains palladium, some of it will hitch a ride, either by drag down, or even by being precipitated to some degree. Not being a chemist, I don't understand what happens, I just know that gold that comes from a solution bearing palladium, the first precipitation comes down quite contaminated with palladium, and it won't wash out well. It can be pretty well eliminated with a second refining, however. Gold that has precipitated from a solution that bears palladium tends to precipitate quite dark, not light in color.

Harold
 
Easy way to remove palladium from gold is nitric acid. Palladium will dissolve giving a dark, dark yellow solution.



Lou
 
Lou and Harold

Thanks for your reply's. This is quite a learning process but fun. I love chemistry and haven't done any in years. But it's starting to come back. I'll get the process down to a tee but i gather it will take some time. This forum is great!

If you guys want to check out a good forum that talks nothing but GOLD but the finance part of it not the chemistry part, check this out. These guys knew GOLD was going to $1000 - 5 years ago. You can read the old posts. True GOLD bugs. There is something about that metal....

http://www.usagold.com/cpmforum/

Cytek
 
The test swabs in the photo don't have the look I'm used to seeing with Pd. The color is more gray in the photo which I typically see in dilute gold solutions. Pd will start off yellow-orange and slowly change to blue-green. I'm figuring the orange color on the towel is just the pregnant solution and not a reaction to the stannous. The purple is obviously gold.

A fast, strong blue-green is a good indication of concentrated Pd solutions. With very concentrated Gold and Pd in the same solution the swab will be black like pitch which makes the determination of the Pd content near impossible.

Typically when low gold concentrations are mixed with traces of Pd and tested it shows gold with yellow-orange first and the swab slowly turns blue-green after some sitting. If it's traces of Pd the blue-green color will go away by morning.

To be sure I'd test with DMG to confirm the presence of Pd before wasting any time evaporating or chemicals trying to get something that's not there.

Harold's suggestion about the stock pot is where the solution would end up in my shop after dropping the gold. I've learned the lesson he mentioned about too little to mess with the hard way. You can waste a lot of time chasing a faint positive Pt or Pd to stannous, with very little return at the end of the rainbow. Save it up and drop everything with zinc to get the most out of your time and chems once you have a larger quantity. I keep my stock pot evaporated down to get the most out of my storage space.

I've posted some photos of positive swabs for Pt, Au, and Pd in the General Reaction List under Stannous Chloride. You can get there quickly using the Guided Tour Link in my signature line.

Steve
 
Thanks Steve:

Your right. I dropped with SMB last night and tested the solution after siphoning off and it tests clear. So the black was as you say a occurs in a dilute gold solution.

cytek
 
Lou said:
Easy way to remove palladium from gold is nitric acid. Palladium will dissolve giving a dark, dark yellow solution.
Lou
Click to expand...
I've not been very supportive of the idea of washing precipitated gold with nitric. Having come from a chloride solution, it's all too easy to re-dissolve some of the gold. What are your thoughts on that, Lou?

Harold
 
I'd like to remind that palladium
dissolves in nitric in a peculiar way,
not like silver smooth dissolution.
 
@ Harold---proper washing will remove any chlorides present. I assumed this would be a given.



@Lino---very true, but for small quantities of Pd that are with gold (say less than 5% Pd with the balance Au), there should be virtually no formation of hydrous Pd oxides that crash out.
 
Lou said:
@ Harold---proper washing will remove any chlorides present. I assumed this would be a given.
Click to expand...
The reason I asked is my experience in washing gold indicates that it's not all that easy to eliminate the chlorides, even with vigorous rinsing with boiling water. I concede, the amount remaining is small.

Harold
 
Well you've probably rinsed thousands of ounces of gold more than I have.


I'm in the lab on Monday--I will put this to the test with silver nitrate. I'll add some HCl to gold powder, rinse it with water several times, and then let the powder steep in distilled water. Decant off the water and add a few drops of AgNO3 and see if any precip. is formed.
 
Lou said:
I'm in the lab on Monday--I will put this to the test with silver nitrate. I'll add some HCl to gold powder, rinse it with water several times, and then let the powder steep in distilled water. Decant off the water and add a few drops of AgNO3 and see if any precip. is formed.
Click to expand...

Sounds like an interesting method.

I was quite fastidious in my washing procedure, as you might imagine. I don't recall ever drying gold without smelling fumes of HCl, that after a hard boil in water after the final wash. Could be I could have rinsed more times and eliminated the acid, but it was too time consuming, and my final wash generally yielded no color. I wasn't concerned about contamination, so I simply eliminated the traces of acid by heating.

Harold
 

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