# Classic Hoke Platinum and Palladium Refining



## kadriver (Jul 30, 2013)

In a previous thread, I tried my first platinum refining and gained much knowledge and experience.

In that thread I used sodium chlorate to try and precipitate some palladium salt after extracting the platinum salt with ammonium chloride.

None of it came out too good and the palladium was very black - but I saved it on a filter paper.

I took the filter paper out of storage and put the black powder from the filter into a beaker and dissolved it with aqua regia.

Here is what the material looked like;

Edited one time to change a word for clarification


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## kadriver (Jul 30, 2013)

Here is what it looked like after adding a few ml of AR and some heat - it took a while but it finally all dissolved and turned a burgundy color.


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## kadriver (Jul 30, 2013)

A stannous test showed the presence of Palladium and some platinum (as far as I could tell).


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## kadriver (Jul 30, 2013)

I am going to use Hoke's book as a guide to try and get a rough separation of the two metals according to the directions given in her book.

I'll evaporate this down several times and hydrate with HCl to drive off excess nitric acid until no more brown fumes are given off, then procede with getting the orange powder Pt and the red powder Pd.

If successful, I'll save these rough samples until I get an ounce or two of each, then try a bromate hydrolysis experiment to see if I can get the Pt.

kadriver


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## solar_plasma (Jul 31, 2013)

I love those commented pictures of stannous tests. I understand the yellow ring is palladium and the brown spot is platinum (please correct, if I got that wrong). Did the brown colour occur immediately? I've read somewhere people waited to the next day for the brown colour.


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## NobleMetalWorks (Jul 31, 2013)

Kadriver makes some of the best posts. 

Kadriver, I can not only appreciate how clean your work area is, and the equipment you use, but also the fact you spend so much time taking the pictures, and then on top of that you put so much time, effort and energy into posting them on this forum.

It's much appreciated!

Scott


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## kadriver (Jul 31, 2013)

Glad these photos are appreciated.

With respect to the stannous test, the brown is the palladium, and the bright orange is platinum.

The liquid I tested from the beaker was orange in color to begin with.

After adding a drop of SnCl, the brown appeared immediately with the orange color forming a jagged ring around the brown.

If the Pd is highly concentrated, then the it will turn green.

kadriver


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## kadriver (Jul 31, 2013)

For this thread I used the process in Hoke's book out of chapter XIII entitled "The Stock Pot"

I began on page 147 under the heading "The Dilute Aqua Regia Solution - Platinum, Palladium, Gold".

In her book, she has collected the PMs from the stock pot with zinc shavings.

Instead of PMs from the stock pot collected with zinc shavings, I got my material from a previous refining in the form of some mixed platinum and palladium salts and I dissolved these salts in aqua regia.

So we both (Hoke and I) have platinum and palladium dissolved in aqua regia (hers from mixed blacks cemented on zinc and mine from Pt & Pd salts from a previous refining), so the process from this point forward should be identical.

I began this morning with the evaporation to a syrupy state of the solution then added some hydrochloric acid to rehydrate and drive off the excess nitric acid.

In the photo, you can see the brown fumes that formed after I added the HCl. I put the cover on before adding the HCl so I could detect the fumes - with the cover off the fumes would not have been visible - After the rehydration and after the fumes were gone, I removed the cover to continue the evaporation.

I repeated this process four times, on the last hydration with the cover on there were no fumes produced upon adding the HCl. I took this lack of fume production as an indication that all the nitric acid had been driven from the solution.

I then concentrated the solution by evaporation again in preparation for adding the NH4Cl to precipitate out any platinum in the form of the "orange powder" spoken of in Hoke's book - I estimated that there was about 3 grams of PMs (just an educated guess) and that is what I based my calculations on for the concentration of the solution.

I reviewed the book at this point and realized that I skipped a step - adding a few drops of sulfuric acid to "throw down any lead and facilitate the expulsion of the excess nitric acid". I wont forget next time


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## kadriver (Jul 31, 2013)

Next I prepared two solutions;

The first is a concentrated solution containing 37.2g of ammonium chloride dissolved in 100ml of distilled water - I multiplied these numbers by .25 as I knew I would not need 100ml, so I ended up using 9.3g NH4Cl and 25ml distilled water. I zapped in the microwave for 10 seconds to get it to dissolve faster.

The second solution was some 15% NH4Cl for rinsing and washing the precipitated platinum salts - plain distilled water will dissolve the Pt salt but 15% will not (or not much anyway).

I added about half the concentrated ammonium chloride solution to the warn concentrated PGM solution and there was an immediate reaction as the solution turned cloudy. Then I could clearly see the orange powder precipitating and falling to the bottom of the container.


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## kadriver (Jul 31, 2013)

Next I poured the solution through a fluted filter paper to get the precipitated orange powder.

I removed it from the funnel and spread it out to dry.


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## kadriver (Jul 31, 2013)

I then went back to the filtrate which contained the palladium.

To this I added a few crystals of sodium chlorate and again there was an immediate reaction - the red palladium salt began to form.

There was much more palladium than there was platinum. Watching the red powder form was the highlight of the day for me.

Hoke said to heat the solution to almost boiling before adding the sodium chlorate crystals, but I accidentally skipped this step and just added the chlorate to the luke warm solution. When I left the shop tonight there was still chlorine gas being produced (I probably added too much chlorate) and the supernatant over the red powder was nearly clear of color.

I am very pleased with the results of this experiment so far and have declared (to myself) that it has been a success.

I plan to repurify the red Pd powder by dissolving it in ammonia and then precipitating the pure yellow Pd salt by re-acidifying with hydrochloric acid.

More to follow.

kadriver


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## Smack (Aug 1, 2013)

Cool, nice work from you as always.


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## butcher (Aug 1, 2013)

kadriver, 
This (tutorial) is like a breath of fresh air, we needed on the forum, thank you for sharing.


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## niteliteone (Aug 1, 2013)

Thanks Kad...
Again you are giving world class instructions that even I can learn from.
Keep up the great work.


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## kadriver (Aug 1, 2013)

Thanks for the kind words.

I took the info from Hoke and turned it into pictures (except I missed a couple of steps).

They say a picture is worth a thousand words - I agree.

Butcher, I would hesitate to call this a tutorial since its my first time, but I guess that's what it is.

When I became a member of the forum I would have loved to stumble across a post like this, but there were none.

Just trying to give back to the forum what the forum has taught me.

kadriver


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## freechemist (Aug 1, 2013)

Kadriver, again, thanks for sharing.

I have read the previous thread, you mention, but did not comment on it. Now, I am quite sure, that you are dealing with significant amounts of iridium, too. This is well documented with some of your pictures, what I try to show you in the attached pdf-file.
View attachment Iridium_in_Classic_Hoke_Platinum_and_Palladium_Refining.pdf


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## kadriver (Aug 2, 2013)

freechemist said:


> Kadriver, again, thanks for sharing.
> 
> I have read the previous thread, you mention, but did not comment on it. Now, I am quite sure, that you are dealing with significant amounts of iridium, too. This is well documented with some of your pictures, what I try to show you in the attached pdf-file.



This is great, I was wondering why the material turned black way back last year.

The sight of that black material in the filter paper really dampened my enthusiasm for PGM refining - I thought I had done something wrong and ruined the batch.

I think it was lou who pointed out to me to go ahead and dissolve it in aqua regia.

This time It came together a little better and things made a little more sense, until now.

The iridium is like a new fly in the ointment - but I guess I had better get busy and try to figure out what to do.

Thank you for that PDF file.

kadriver


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## kadriver (Aug 2, 2013)

When I arrived at my shop the next day this is what the container looked like.

The red powder was settled out and the liquid was a light pinkish color.


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## kadriver (Aug 2, 2013)

I set up a fluted filter paper and gravity filtered the red powder from the liquid.

Hoke said to add a crystal of sodium chlorate to the filter - so I did.

I used 15% ammonium chloride solution to rinse the red powder from the beaker into the funnel.


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## kadriver (Aug 2, 2013)

After rinsing the red powder with a minimal amount of ammonium chloride, I removed the filter and spread it out to dry on paper.


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## kadriver (Aug 2, 2013)

I rinsed the beaker with water to dissolve all the traces of red powder and added that to the filtrate.

Then I rinsed it all into a 3 liter glass jar and covered it with paper towel to keep trash out and allow the solution to evaporate and concentrate.

This 3 liter jar will be my PGM stock pot for now.


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## Lou (Aug 3, 2013)

Looks more like rhodium aqua cation than iridium in the last filtrate.


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## kadriver (Aug 3, 2013)

The source of this material was catalytic converters leached in HCl/Cl cemented with zinc shavings.

Is there iridium in catalytic converters?

Thanks for the help.

kadriver


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## lazersteve (Aug 3, 2013)

Kevin,

Have you performed the stannous test for Rhodium?

Steve


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## kadriver (Aug 3, 2013)

Steve,

You posted that test in a previous thread that I started during my first attempt to do a PGM refining.

I'll go back and find it, then see if I can do the test.


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## lazersteve (Aug 4, 2013)

Kevin,

You can find it quickly in the Guided Tour Link--> Reaction List.

Steve


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