Platinum solution

[jeweler1]

I have a very complicated Platinum solution to precipitate .It has Iron, Chromium, Nickel, and Platinum metals in it. It also contains Sodium Nitrate, Sodium metabisulphite, and HCL. I was going to first concentrate it to eliminate the Nitrate and than add Ammonium Chloride to create Ammonium hexachloroplatinate which I can filter out. I have done this with another solution but not one this complicated?
Could I use Zinc to drop the Platinum first without concentrating it? Than redissolve it to get purer metal without the other metals and chemicals present? Or would the Zinc also drop other metals?
When I concentrate it I will get a lot of crystals forming from the other chemicals present. This traps some of my Platinum before I can precipitate it.
I want the Platinum as pure as I can get it. Redissolving it several times is acceptable.
I use the Platinum video as my guide (thanks) but I am not a chemist.

 

[etack]

If you where to drop with Zn everything will come out. then you can rinse, heat to red , and wash with nitric to be rid of all of the other metals. Pt should be left.

Eric

 

[nickvc]

I'm thinking that cementing the values using copper would be the way to go as it would remove most of the other metals from your next dissolution, about which I agree with Eric, I'd use nitric first and then re refine the residues by the solvent of your choice.

 

[etack]

I'm thinking that cementing the values using copper would be the way to go as it would remove most of the other metals from your next dissolution, about which I agree with Eric, I'd use nitric first and then re refine the residues by the solvent of your choice.

I thought that Cu and PMGs had a harder time separating when cemented on Cu. This could just be Pd though I will have to read up on it.

Eric

 

[jeweler1]

Following Eric’s advice
“If you were to drop with Zn everything will come out. “
And following the Platinum video I added Washing Soda (Sodium carbonate) until I got a white precipitant than added Zn to drop the Pt. My new vacuum filter system works much better than Coffee filters did. I than redissolved the precipitant in AR (filters and all) (no waist) and refiltered. I went from 1 gal very dirty solution to 800-ml concentrated and clean solution. See picture
Thanks for the help.
This question is about the next gallon I have (4 in all) same stuff just more concentrated Pt in it.
About the pH level in the video it says to have a range from 3 to 5 yet in the video he only looks for white percipient. I have tested the solution with 2 different pH test strips one tests 1.0 and the other is 7.0 and I have no white precipitant after adding 11 spoons of Washing soda.
Any suggestions before I add Zn?

 

[butcher]

“I have tested the solution with 2 different pH test strips one tests 1.0 and the other is 7.0 and I have no white precipitant after adding 11 spoons of Washing soda.”



That is a very wide spread of pH, it should be easy to tell if solution is acid or neutral, do you have a vigorous reaction if you take a small sample and add a sprinkle of baking soda.

You may also be able to get an Idea of how acidic solution is by its reaction when you add a little zinc to it.

Zinc would dissolve into solution and cement even if solution was very acidic, but you would be using much more zinc, my guess for raising pH is to get same results without using so much zinc.

If pH was neutral pH7 the cementation process may slow or stop, thus you do want it to be at least slightly acidic.

 

[samuel-a]

Zinc would barely be able to replace Ni,Cr and Fe in dilute acidic solution.
It will however drop a bit more in a concentrated solution, though not quantitatively.

Also, keep in mind that Zinc wil eventually raise the pH on its own as it saturate the solution.
I have never raised pH before Zinc treatment and find it is not a needed step unless you have a lot of free acid.

From the points above, you can deduct that working with too high pH, may form hydroxide and/or cemetation of base metals which will follow your Pt powder in to the next treatment, as seen by the green solution in your picture.