Pd/Pt/Au solution puzzling reactions

[kjavanb123]

Hi everyone

The jewler whom I gave my last batch metals to melt, gave me a 2.79 grams sample he claimed to contain mostly gold and a little platinum.


So based on that I made an AR solution and boil the sample in it.

I got immediate reaction and solution turned brown which indicated some palladium there

Few hours into reaction upon addition of hcl a white cloud formed and settled as silver chloride

This platinum palladium and gold AR solution after I filtered the silver chloride and washed the powder with hot water.


Here is the stannous chloride testing solution showing a deep purple yet brown color,


Added DMG solution dropped the palladium as the canary yellow, filtered it and got this green color solution that should have only gold and platinum,


This is the stannous chloride testing solution of filtered solution,


Please see more in the next post which is really puzzling for me.

 

[kjavanb123]

So continued from last post

Since I already had used excessive nitric acid to dissolve the sample, I brought the gold platinum solution to near boil and added sulfamic acid to expell the nitric.

This is what happened, addition of sulfamic to gold platinum solution which already DMG added to percipitate palladium turned brown and after cooling brown powder settled which was gold!








And after I filtered this gold tested the solution with stannous and got orange which indicates platinum.


I ended up separating and refining all 4 metals and gave them to the jewler but this is really puzzling as I was on impression that DMG would only drop palladium from a solution that has gold in it

But based on this observation, addition of sulfamic acid to DMG solution did percipitate gold as well.

Best regards
KJ

 

[cuchugold]

If Pt or Au are present in solution with Pd, and you apply DMG, some Pt and Au will contaminate your Pd.

If you have a little Pd contaminating a Pt and/or Au solution, and you apply DMG, it'll scavenge all of the Pd and also drop a little Pt and/or Au.

That was my experience with DMG. Excellent scavenger of Pd. In Silver nitrate solutions too.

 

[Lino1406]

Generally DMG solution contains ethanol. What in the present case?

 

[anachronism]

Generally DMG solution contains ethanol. What in the present case?

Depends how you make it. Some make it with Lye.

 

[kjavanb123]

DMG solution I used is the same as always, 5.81 g DMG and 100 ml hot water which 4 gram lye already dissolved in it. No ethanol was used

 

[Lou]

In the right pH conditions the DMG/lye composition can be a reducing agent for gold.

My experience with DMG is in DMSO (dimethylsulfoxide) and in ethanol and only used for determining Pd, never for separating it, as it's too expensive and operationally horrible to consider.

 

[kjavanb123]

In the right pH conditions the DMG/lye composition can be a reducing agent for gold.

My experience with DMG is in DMSO (dimethylsulfoxide) and in ethanol and only used for determining Pd, never for separating it, as it's too expensive and operationally horrible to consider.

Thanks Lou. Forgot about pH effect.