# Questions and Comment Pt Precipt with KCl



## lazersteve (Aug 21, 2011)

Here's where you can post your comments and questions on the newest Pt video I posted.

You can find the tutorial here:

Pt with KCl

Steve


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## qst42know (Aug 21, 2011)

How long does it take to settle?


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## lazersteve (Aug 21, 2011)

It settles in 20-30 minutes tops.

If you leave it longer it will compact itself a little, but I usually vacuum filter it within an hour or so of everything falling out of the solution. 

The purer the salt the quicker it seems to settle, much like gold.

Steve


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## rusty (Aug 21, 2011)

If the KCI is left to sit longer than 1 hour after the PT had precipitated will it also drag down iridium if it was also in the solution being treated.

Regards
Rusty


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## lazersteve (Aug 21, 2011)

Rusty,

Iridium contamination in the platinum salt is also possible via drag down if the iridium content of the solution is above 5% and the solution is very concentrated. 

Evidence of iridium contamination in the platinum salt is a brick red or maroon-flesh tone to the platinum salt as seen in this photo:







You can clean the brick red salt of iridium by reducing it with zinc, or many other methods and dissolving the resulting powder in dilute AR at or bleow 50C. The iridium will remain behind as a fine black powder. After filtering the solution the resulting Pt salt will be precipitated as the familar canary yellow color seen in the video above. 

There are other methods of removing the Ir involving using basic solutions and oxidizing the iridium to allow it to separate from the Pt.

Steve


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## skippy (Aug 22, 2011)

Steve, that seems pretty clean and easy. Are there advantages to KCl over ammonium chloride? 
The supernatant looks like it has dropped the vast majority of the values.


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## lazersteve (Aug 22, 2011)

This reaction works at the same speed as ammonum chloride. 

This was the third refining of the same sponge. Starting weight of the sponge was 61.4 g this time around, new weight of reduced sponge was 60.7 g. From this I assume less than 0.7 g to be left in the solution as the sponge shot 99.8% on XRF prior to dissolving.

Now all I need is a buyer.

Steve


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## rusty (Aug 22, 2011)

Steve do you think that if I had used KCl (potassium chloride) my platinum precipitate would have come down cleaner without the green snot.

Regards
Gill


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## lazersteve (Aug 23, 2011)

Gill,

The green snot is most likely a mixture of organics and base metal salts from the source material. Potassium chloride won't solve that problem. Reduce the dirty salt, heat the resulting black/gray powder to red heat, wash with boiling HCl, filter and digest the solids again in your favorite PGM solvent.

Steve


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## HAuCl4 (Aug 25, 2011)

Nice video Steve!. What are the pro's and con's of that KCl versus the classical NH4Cl precipitation?. How do other PGMs contaminants react to this KCl drop versus the classical drop?. :?: 8)


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## newt3947 (Dec 22, 2014)

Hey Steve. What did you use to rinse the salt as you were filtering it. Thanks.


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## lazersteve (Sep 17, 2017)

The two primary advantages of using potassium chloride over ammonium chloride are:

1) You will keep ammonia out of your processing and waste stream. Ammonia easily forms many explosive compounds which can unexpectedly ingnite and/or explode. Additionally, toxic ammonia gas is formed during the waste neutralization phase if it is used during the processing phase. Trust me, unforseen ammonia clouds are no fun.

2) Potassium salts are easier to wash due to their solubilty. I still use dilute potassium chloride and water to rinse the Pt salts.

The one disadvantage I can see to using Potassium chloride is that the potassium salt remains mixed in your refined Pt after calcining. Ammonia chloride will mostly go up in smoke. You can remove the KCl easily by boiling the refined Pt sponge in water or just melting the Pt and it will separate from the KCl leaving a purple white crust in your dish. KCl also forms a whitish vapor at the melting point of Pt.

Steve


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## Yggdrasil (Oct 10, 2017)

Just a question regarding this. 
Will any chloride salt precipitate the PGMs from solution ? 
Or is this valid for ammonia and potassium only?


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## Lino1406 (Oct 11, 2017)

CsCl, RbCl will do it


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## Yggdrasil (Oct 11, 2017)

In short, it is the chlorides of Ammonia and Potassium which is most accessible ;-)


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## Lou (Oct 11, 2017)

One fundamental difference from ammonium hexachloroplatinate is that K2PtCl6 precipitates more completely from aqua regia solutions than (NH4)2PtCl6 because there are no side reactions.

Remember all, ammonium hexachloroplatinate is soluble in aqua regia. In fact, one can take the yellow salt and redissolve it entirely in aqua regia; NOCl is a strong enough oxidant to oxidize ammonium cation to water and NOx.


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## Yggdrasil (Oct 11, 2017)

Thanks for the clarifications Lou.
How will the other PGMs react to KCl?
Will they too Precipitate or will the Palladium chloride behave like Hoke describes in page 108 
and need addition of Sodium chlorate to precipitate?


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