# Precipitate rhodium from platinium solution



## denzel759 (Jul 14, 2017)

Hi all, i want to ask Is there any way to precipitate rh from pt solution ? i use hydrogen peroxide to form pt and rh solution, and drop with saturated amonia chloride, but this method also drop rh, from what I know.

And second question is, how can i check if solution contains rh, there is different colour in stannous test ?


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## Lou (Jul 14, 2017)

The co-precipitation of Rh with freshly boiled chloroplatinic acid solutions at low acidity is minimal, though your platinum salt may have a greenish twinge. By low acidity, I mean <1 M HCl. That (NH4)2PtCl6 can be redissolved in aqua regia to give H2PtCl6 that has a slight rhodium red to it and precipitated once again. That's usually sufficient to meet even the ASTM/ISO specs for 99,95 Pt. 

To fully purify it, you will need to conduct a bromate hydrolysis. You can alternatively take the rhodium solution, make pH 7.5 with sodium hypochlorite, boil it briefly, and then add in a flocculant to collect the rhodium hydroxide.


The rhodium may be nearly quantitatively recovered by increasing the acidity above 6M in HCl to favor [RhCl6]3- and precipitating with ethylenediammine*HCl or some other suitable organic amine salt.


Lou


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## denzel759 (Jul 14, 2017)

Thanks for good advice, you explain this very well. 99.95 is pretty nice fine fo me. but still is second question, how can i check if there is rd in solution ?


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## denzel759 (Jul 14, 2017)

What do you mean about freshly boiled ? that i can add amonium to hot solution and will be better than cold ?


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## Lino1406 (Jul 21, 2017)

" i use hydrogen peroxide to form pt and rh solution," what is the source material?


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