# Separating Pt from Au



## Anonymous (Oct 19, 2009)

I alloyed some karat Au jewelry scrap and also some pure platinum buttons. I was going to make my wife a bracelet but never got around to it. I used an induction coil to melt everything and mix the alloy. I don't know the exact percentage, but out of 1.5 oz of jewelry scrap I had about 20 grams of Pt. 

I'd like to separate them back out again. Here's my plan so far - Melt alloy and make corn flakes. Dissolve in AR. That's all I've got so far. I want to precip out both the Au and Pt, but I'm not really sure of the sequence. Precip Pt first and then Au or ?... Anyone got any experience with separating these?


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## Harold_V (Oct 19, 2009)

You made no mention of the amount of silver that may be included. A direct digest in AR may not be easy, although if you melted already alloyed gold with platinum, I expect the silver will not be a significant problem. 

You are unlikely to get a clean separation at the outset. The resulting silver chloride will absorb some of the values, which will be difficult to wash completely free from the silver chloride. You can deal with that problem by converting the silver chloride to elemental silver with aluminum or steel, which will also convert any dissolved values back to the elemental state. You can then re-dissolve the resulting material with nitric, separating the silver from the traces of values. 

As far as selectively precipitating the gold and platinum, my routine was to always precipitate gold first, even if I had to re-evaporate the remaining solution in order to achieve an extraction of the platinum metals. 

Reason?

Precipitated gold is easy to wash chemically, very unlike the salt of platinum that is the result of precipitation with ammonium chloride. If you precipitate platinum first, the resulting salt will be heavily contaminated with gold, and will border on the impossible to remove due to the salt being water soluble. 

Harold


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## markqf1 (Oct 19, 2009)

Harold,
Is this one of those cases where using AR cold, then hot, after inquartation could be helpful?

Mark


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## Anonymous (Oct 19, 2009)

Thank you Harold - This is exactly what I needed. I don't suspect the silver will be a problem but I had already anticipated separating the small amounts of values from the Silver Chloride just as you suggested. Where I was really stuck was the sequence of precipitating out the the Au or Pt. I wasn't sure how much Au the Pt salt would retain given an almost 1/3 conc of Pt. Glad I asked and I really appreciate your time.

Best Regards


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## Harold_V (Oct 20, 2009)

markqf1 said:


> Harold,
> Is this one of those cases where using AR cold, then hot, after inquartation could be helpful?
> 
> Mark


I'm of the opinion it won't make a significant difference. Once you've melted platinum and silver together, platinum dissolves in nitric acid alone, so you start out with a loss of platinum that you can't recover until you have parted the silver in a silver cell. Also, finely divided, as it would be having been inquarted, I expect that even in cold AR, platinum will dissolve far more than you'd like. I agree that it would be slightly more selective, but hardly the solution to the problem. 

Platinum is slow to dissolve in the solid state, so you could take advantage of cold versus heated in that example so long as there is no silver included. I used to pickle platinum for my customers, free of charge. I'd keep anything that dissolved, and they got back platinum alloy that had been fully cleaned of any solder joints so it could be re-used. For the record, traces of silver in platinum render it quite hard (loss of ductility)----much the same as traces of lead in gold. 

Harold


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