# precipitating platinum(from cats containing pt,pd,rh)



## arthur kierski (Dec 14, 2008)

lately when precipitating pt with nh4cl i get a greenish precipitate or a strong brownnish black pprecipitate---i suppose is ptsalt contaminated with rhsalt---if this is correct,what must i do to separate the rh from the pt??


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## lazersteve (Dec 14, 2008)

Arthur,

If you are using nitric acid in your process, you may be forming some double chloride nitrate salts. Also green Pt salts are not uncommon with Rhodium contamination. 

Palladium contamination is also a possibility with dark powders.

To purify from Pd add ammonium hydroxide, stir, and filter out sediment.

Sediment contains Pt and Rh salts. 

Color of sedimentary salt should change after treatment.

Pd will follow liquid and some Rh and Pt.

Precipitate yellow Pd with HCl.

Boil filtered sediments in HCl and denox.

Filter, combined remaining solutions and add zinc if positive for PGMs.

Treat zinc precipitates as usual.

Stannous test a small sample of all separated powders with a drop water to determine Pd, Pt, or Rh content.

Steve


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## arthur kierski (Dec 15, 2008)

thanks steve for your reply---as i have to do all this to separate the rh ,pt and eventually pd ,could i with hidrazine return all to black powder and then separate one from other? hno3--for pd----ap for pt and them the powder left would be rh?


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## lazersteve (Dec 15, 2008)

I would think cutting to the chase and redissolving the whole batch as you suggest, then precipitating would be a better solution actually.

Steve


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## Lou (Dec 15, 2008)

Greenish color ammonium hexachloroplatinate is strongly indicative of rhodium contamination. 

Brownish color means Ir.


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## arthur kierski (Dec 15, 2008)

LOu,it did not cross my mind that the brown powder could be iridium---thanks for the reminder---steve , any way i am going to do the hidrazine method to separate the now(perhaps )4 metals---will pass results to the forum


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