# Rhodium?



## kjavanb123 (Feb 16, 2016)

All,

While toll refining a lithrage from another smelter for scrapper who brought it to me, I dissolved the silver alloy from the smelt in nitric and got the following solution,



To that solution soda ash was added to bring the pH to 3, then using the minimal amount of zinc powder, percipitated the grayish black powder, which once dried weighed 38.4g.



After dissolving that powder in 50/50 nitric acid, the solution tested positive for Pd, but the undissolved powder showed a light gray color which I had seen in Rhodium,



Decanted the solution added more nitric, this time solution turned black in color, and the gray powder did not change, so I decanted the black solution and washed it with water few times, then added concentrated sulfuric acid, assuming if powder is Rhodium, boiling it in concentrated sulfuric acid would dissolve it, but strangely it turned orange as seen in the following photo, and residue also turned white from gray,



It boiled for 20 mintues but since the color did not change I figured this is not Rhodium, or should I have left it boiling for hours? So I decanted the orange solution into a beaker half filled with water, and water turns purple, as can be seen in the photo, water was added to the white powder and solution is light purple,



I am hoping experienced members like Lou can guide me here, based on the reading the thread by Lazersteve here about Testing For Rhodium, the color of solution turns red rose with stannous chloride so I am guessing might be Rhodium but have to leave it on gas for longer.

Regards
Kj


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## kjavanb123 (Feb 16, 2016)

Here is the stannous chloride testing solution result with samples from the PGM solution as zinc added to percipitate PGM mix, it starts from 12 o clock position and counter clock wise to 8.


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## Lou (Feb 16, 2016)

Pt.

Rh is not soluble in silver.


Best,

Lou


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## kjavanb123 (Feb 16, 2016)

Hi Lou,

Thanks for your comment. I wonder why the fine powder after addition of concentrated sulphuric acid turned color from gray as visibile from the first photo to purpule as seen by last photo?

He gave me 3 grams of what he claims to be Pt, as seen in this photo,



Added nitric acid 3 times, no color change but once I added muratic to nitric washes it showed presence of silver. Here is the beaker on the right containing Platinum sponge uneffected by hot concentrated suphuric acid, the left beaker is reacting with concentrated sulphuric acid, so please advise Lou the color change on beaker on the left is due to silver contamination being dissolved by sulphuric acid?



Finally I tried to dissolve the Pt powder in mixture of hydrochloric acid and hydrogen peroxide 35%, this photo is taken after 5 mintues I will have to check it out this morning,



Best
Kj


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## nickvc (Feb 17, 2016)

Kevin your adventures continue 8) 
I will post my thoughts on refining PGMs.
The salts or most are highly toxic and downright dangerous to touch or inhalation or both, as I'm sure you are fully aware, unless forced by necessity to refine these materials I would simply recover and then do a melt and assay to determine the value. Please follow full safety guidelines and use proper laboratory equipment when processing this or any similar material, I'm enjoying your journey.


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