# Black precipitated the separation of PGM



## Alquimi (Apr 9, 2011)

hello

I have a doubt, I had an experience where I had a mother solution containing PGM.
The first step I made, after expelling the HNO3 and HCl to reduce the volume of the solution was added KCl, in my case there was no precipitation chloroplatinate, then dilute with a little distilled water and added sodium hypochlorite, with that there were a black precipitate.
The question is, what is this rash?


Thanks :?: :?:


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## Alquimi (Apr 9, 2011)

Sorry, one correction.
My question is what is this precipitate?


Thanks

Alquimi


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## Platdigger (Apr 10, 2011)

Well, if you would have added ammonium chloride and nothing happenned and then you added the bleach, I would say it was pd. But, since you have potasium in the mix and the precip is black, my guess is pt.
Is there enough of the precip to make a test?


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## Alquimi (Apr 10, 2011)

Hello Platdigger;

When added sodium hypochlorite and there was precipitation, filtered and the black powder added HNO3, lead to the dissolution. Could say with certainty that it was AP, but which left me unsure is that the precipitate should be red chloride Pd.
If the precipitate is Pt, then he was not in reduced form, because it could not dissolve in HNO3.
The curious thing was that I repeated the procedure with another water of the same type of parent material and the phenomenon was not repeated. When there is another opportunity to do this study to inform you all.

Thanks

Alquimi :?: :?:


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## samuel-a (Apr 10, 2011)

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=51&t=9712#p93575

see Lou's answer to my question.

I think he is the only one here who could help you.

Why not using Ammonium Chloride?


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## Alquimi (Apr 10, 2011)

Thanks Samuel

I read that Lou wrote, I understand that the solubility of the complex formed with KCl is higher than that formed with NH4Cl. But I worked with the concentrated solution to apply this technique. But the very next work will come to use the NH4Cl for no more doubts.

Thanks

Alquimi :?: :?:


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## freechemist (Apr 13, 2011)

Hello Alquimi,

Did you determine the pH-value of the overnatant solution after settling of the black precipitate? Was nickel present in your mother solution containing PGM?
Sodium hypochlorite solutions usually are made up from lye (NaOH) and chlorine and therefore are alkaline. If a solution containing nickel is made alkaline, pale green nickel-(II)-hydroxide, Ni(OH)2 precipitates, which is quickly oxidized by hypochlorite to black nickel-(III)-hydroxide, Ni(OH)3. This can readily been redissolved in acid, loosing it's black colour.

freechemist


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## Alquimi (Apr 14, 2011)

Hello freechemist,


Very interesting, because I know that in my sample contains nickel.

Very enlightening their response.

Thanks

Alquimi :?: :?:


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