gold, platinum and copper

[MetalMan76]

When using Sodium hydroxide in an AR solution of gold, platinum and copper, in what order will they drop as I continue to add Sodium hydroxide?

 

[lazersteve]

I've never used lye to separate precious metals from base metals. I don't think the separation would be clean.

Copper Hydroxide is blue-green.

Here's the wiki:

Copper Hydroxide

Why don't you use the well known methods to precipitate the gold and platinum selectively like everyone else?

Steve

 

[MetalMan76]

I wanted to know what order they drop.... not color.

 

[lazersteve]

If you insist on using lye, then the color of the precipitate is important. When the precipitate changes from blue-green to brown-black the copper is all out, filter out the blue-green copper hydroxide then use the well known methods to separate the gold from the platinum.

I'm still wondering why you don't just precipitate the gold and platinum from the solution. You will end up wasting a lot of reagents and time trying it your way. There is a reason we use the reagents we do when refining; it's because they work.

You will not get a clean separation using lye.

Steve

 

[MetalMan76]

So your saying the copper will drop out first before other metals?
I agree with you 100% Steve. I will precipitate the gold and platinum from the solution using conventional methods. I just wanted to get better understanding of the reaction using Sodium hydroxide and the order of the metals that will drop out as the PH level increases.

 

[lazersteve]

The activity series chart is a good starting point for the order of reactivity of the metals.


Steve

 

[MetalMan76]

Steve, I greatly appreciate your time and patience .

 

[butcher]

theoretically it will work, but makeing it work practically is a whole different story, chemistry does not always follow the rules, and even when it does there may be varibles hard to control, you will find the proceedures we use work, selective seperation of metals using Ph theoretically will, but making it happen is not a viable option, listen to steve, look at conventional methods, or try seperation of less valueable metals as expieriment, you may see how hard it is to do.

 

[MetalMan76]

I tried an experiment with less valuable metals as u suggested, and your right, way too difficult and really time consuming. But I did enjoy the experiment. It was interesting. I did have one metal precipitate out a deep yellow/orange color using Sodium hydroxide. I have no idea what it is... May anyone have a suggestion on what it could be?

 

[Platdigger]

Was there iron in the solution?
It may have been iron.
One thing a guy could try is to use say hydrazine sulphate adjusting the ph with sodium hydroxide incrementally.
I know platinum comes down best at a certain ph, not sure if there would be enough difference in ph between that and gold and then the copper to make a good seperation or not.

 

[butcher]

I would think that you may have more than one metal in that test tube, if you wish to spend your time on it you could recrystalize to help seperate it further, and also most all cations and anions can be tested to determine what they are.
I would put that study on back burner and look into learning to refine valuble metals. for me studying that is more fun and rewarding.