platinum +silver

[HAuCl4]

I've used sodium, potassium, and ammonium formate for in situ reductions of Pt (II) and Pt(IV) when doing organic chemistry as a researcher in college.

A curious thing to note is the shift to a sickly green hue as Pt(IV) --> Pt(II) --> Pt(0).

Lou

I plan to attempt this one sometime in the future. Thanks for the clarification.

 

[samuel-a]

Lou,

Since you first posted about the 'sickly green' reaction in a previous thread, I have tried using zinc to reduce my ammonium chloride PGM salts and found that it works just as you described. It was really no surprise that it worked, it's just amazed me that it worked so well!

The four times I've used zinc and dilute HCl to reduce my PGM salts I was initially worried that I did not see a noticeable reaction with the PGM salt as I added the zinc and it began to dissolve. I stirred and added more zinc as needed and then all at once the color shifted to the drab green color and the PGM salt quickly converted to a nice gray mass.

Here's a snapshot of the final precipitate:

I like this method way better than calcining. The one thing I noticed is that when I melted the resulting metal I got a distinct blue residue on the surrounding firebrick. Do you know what this blue may have been from? I washed the precipitated PGM with dilute HCl to remove any excess zinc, so I'm at a loss as to where the blue came from. The PGM in question was Platinum, and the source scrap was Pt/Ir 90/10.

Here's a shot of the firebrick that was over the top of the crucible showing the blue color in question:

I have not seen this color before when melting Pt metal when the Pt salt is calcined, so I assume it's likely residual zinc. What do you think? I did not see any 'zinc cobwebs' when melting the sponge.

Steve

Steve, would you care to elaborate what exactly have you done from the moment that you dropped the ammonium chloroplatinate all the way to metal state reducing?

will the same process work for palladium ammonium chloride ?

Thanks, Sam

 

[lazersteve]

Samuel,

Here it is:

1. Precipitate the PGM salt and vacuum filter it free of solution, rinsing with dilute ammonium chloride solution as typical with PGM precipitations. For Pd salts redissolve in aqua ammonia, filter, and precipitate with HCl before proceeding. This will remove most of the Pt, Ir, and base metals from the Pd salt.

2. Rinse the PGM salt into a large beaker with a spray bottle.

3. Mix up a solution of HCl and water (3 volumes of water to 1 volume of 31% HCl) in a separate beaker and stir.

4. Add the HCl solution to beaker containing the PGM salt.

5. Slowly add in small amounts of zinc turnings (too much will cause a foam over) to the solution with the PGM salt in it. You should see a vigous reaction with the evolution of hydrogen bubbles as the zinc begins to dissolve.

6. Stir the reaction to mix the PGM salt with the dissolving zinc.

7. If the reaction subsides and all of the zinc is gone, add a little more zinc to get it going again.

8. If the reaction subsides and the zinc has not fully dissolved or the PGM salt has not fully converted to a heavy gray powder add a few millliters more of straight HCl to get the reaction going again.

9. Keep stirring.

10. When the zinc level gets to the right point, the PGM salt will begin to change to a 'sickly green' (light olive drab) color.

11. When the color of the PGM salt changes to the green color the reaction is almost complete. From here on out, go very easy on the zinc/HCl additions.

12. Repeat steps 5 through 9 until the sickly green PGM salt is all converted to a heavy gray powder as seen in the above photo.

13. Let the solution settle until the liquid clears.

14. Siphon off the liquid, test with stannous, and add to your zinc wastes when barren. If the stannous test is positive add more zinc to precipitate any dissolved PGMs.

15. Mix up enough dilute HCl (see step 3) to cover the gray powder and soak until no more fizzing occurs. Rinse, Repeat. Stirring periodically helps expose the left over zinc to the acid. Look for tiny streams of bubbles coming up out of the gray sponge.

16. Rinse the gray powder with hot water and stirring, vacuum filter.

17. Melt the gray powder.

Steve

 

[samuel-a]

Good instructions steve, i have a small Pt batch that i couldn't calcine in full and sitting on the shelf for ages, so i guess i'm gonna try that way...

Thanks,
Sam

 

[goldenchild]

Good instructions steve, i have a small Pt batch that i couldn't calcine in full and sitting on the shelf for ages, so i guess i'm gonna try that way...

Thanks,
Sam

Let us know if this method works for you if you have say, some cat beads laying around or something I have probably 50+ pounds of beads and crushed honeycombs that I plan on refining once it gets warm again.

 

[samuel-a]

Let us know if this method works for you if you have say, some cat beads laying around or something I have probably 50+ pounds of beads and crushed honeycombs that I plan on refining once it gets warm again.

lol
:mrgreen:

This is my next project article.