# platinum question



## mls26cwru (Jan 22, 2016)

I have very little experience with platinum and was hoping some of you guys might be able to offer some insight.

I was refining the gold out of some fuzz button interconnect wires and was expecting it to be a gold/copper alloy with the possibility of palladium (from a prior experience). I dissolved the wires in AR. I diluted the solution with H2O, neutralized the excess nitric with sulphamic acid granuals, and filtered. I then dropped the gold out of solution with SMB... I had no problems with this. Next is where my hang up is...

The resulting solution was a burgundy red. I tested with some DMG (in NaOH solution) and got no reaction for palladium. I tested with stannous (freshly made), and got a bright orange reaction. After about 5 seconds the orange diminished in intensity but did not completely go away. From this I was guessing platinum was in there? I mixed up a solution of Ammonium chloride and added to the solution but got absolutely no reaction. no precipitate, no color change, nothing... the stannous test was still the same.

I read some more about platinum solutions, and some how missed a bit about concentrating the solution, so for the last couple days, I have had the solution on a hot plate and have slowly been evaporating the it. What was originally a 500+mL solution is now down to 200mL... but in the process the solution has changed from burgundy to canary yellow . The stannous test now gives me an brief orange flash but after about 2 seconds, diminishes to the same light yellow as the solution. 

This is where I am lost... Is the ammonium chloride finally reacting with the platinum and turning my concentrated solution yellow? Am I maybe getting a false positive on my stannous test? Is something going on because I denoxed with sulphamic acid? Any thoughts or inputs would be welcome as I am having a hard time deciding what to go next.

Thanks a bunch guys!
Mike


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## nickvc (Jan 22, 2016)

Personally I'd simply add copper to cement out any values, PGM salts aren't clever to play with, ask Lou!


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## Lou (Jan 23, 2016)

Sounds like rhodium sulfate to me...rose red in highly chloride rich, acidic solutions as chlororhodic acid. Then you heat it, driving out HCl and it's already got sulfate in it from the sulfamic turning any residual nitric into N2O and making in situ dilute sulfuric. 

If a pretty clean solution with limited base metal contamination, you might consider just cementing it with zinc and then simmering the powder in 30% sulfuric acid and then a wash with strong HCl to remove any silver chloride.


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## mls26cwru (Jan 23, 2016)

Lou said:


> Sounds like rhodium sulfate to me...rose red in highly chloride rich, acidic solutions as chlororhodic acid. Then you heat it, driving out HCl and it's already got sulfate in it from the sulfamic turning any residual nitric into N2O and making in situ dilute sulfuric.
> 
> If a pretty clean solution with limited base metal contamination, you might consider just cementing it with zinc and then simmering the powder in 30% sulfuric acid and then a wash with strong HCl to remove any silver chloride.



Thank you Lou! I will attempt to try this... I figured I would try to evaporate this down to about 100mL's and try cementing this out. I cant imagine much else being in there at this point. I did forget to mention that my initial leech was a nitric leech, so any copper/silver should be gone (i did not get a positive test for silver when i tested said leech though). If this changes things for some reason, let me know, otherwise I will post the results when/if I get any!

M


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## mls26cwru (Feb 1, 2016)

So I have a little update to this. I added Zinc (powder form) as you suggested Lou... I got a bunch of fizzing and after adding about 10 grams in small increments, the solution turned colors and stayed dark. There was not precipitation of any kind prior to the solution turning dark. I gave it time to settle and I noticed that a dark blue substance has collected on the sides of the beaker while the solution is still a very dark. 

The stuff that settled on the walls of the beaker looks more like a heated & sarturated solution cools thus forcing material out of solution... It is not a 'sponge' or crystal. Just a layer of dark blue material. Is this something that is characteristic of rhodium? Any further thoughts? 

Thanks again!
Mike


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