Newbie experience with Pd

Hi all, recently I purchased a small parcel of 627 grams of supposedly silver shot from another home refiner here in Australia. I do not know the source but I was quoted an xrf reading on the metal as .3% Au, .3% Pd with the remainder as Ag, then he said he can't actually remember. After receiving the shot in the post it had a very satin appearance, not the look of shot I am used to.
Yesterday I digested into nitric under heat with DI water approx 750 ml DI, 560ml Nitric total addition to digest. I ended up adding 1oz silver coin to help consume remaining acid.

About 1 hr into digestion, I had no blue/green colour of solution which would be the norm I expect, I checked the silver shot and noted black oxides which I did not anticipate as well as the solution taking a brownish yellow appearance. About 3 hrs into digestion I took 2 samples, tested one on paper with stannous, with brown result, tested the other in a TTube with DMG and the whole sample turned to yellow goo, by the time the shot digestion was completed there was still no separation in the test tube of Pd salts and solution.

I think I have taken a wrong turn in dealing with this batch.
Should I have dropped the silver in solution with Hcl first then proceeded to DMG?
I filtered the residues, noted some chunky pieces of gold and some other White metal in the solids along with black oxides.
I added approx 7g of DMG and dissolved in 600ml of DI water, added maybe 15 pills of Sodium Hydroxide to achieve total dissolution. I started with around 1.7 litres of solution after vessel rinses added to initial shot digest solution, then added DMG approx 300 ml solution, then came the yellow goo precipitate, thinking this DMG addition was not sufficient I added the remainder 300ml DMG solution, I got a dark green instant reaction precipitate, really gluggy, I stirred the solution which now changed from yellow to an off yellow green colour, I left the solution to hopefully settle overnight, this morning still with no separation as in Pd salts rising or sinking leaving me now with 2.5 litres of goo in a 5000ml beaker.
What is the off colour of the Pd salts from? I was under the impression DMG was selective for Pd only?
Do I add more DMG?
I am leaning toward filtering what I have then retest for Pd with DMG on filtrate.
After Pd salts removal can I cement out silver or am I restricted to Silver chloride separation?
I seem to have inadvertently found myself dealing with more Pd than I was prepared for, I wish now I had just cemented the lot out on copper, or dropped the silver with Hcl.
Besides a kick in the bum for not adequately thinking through the steps on this batch, any advice on treating this goo?and following steps?

0.3% Au does not cover all your expenditures and efforts

it was not bought for Au or Pd, in any case I made no mention of the parcel price for 627g which was $370 aud, which was based on Ag content alone.
Thanks for your enlightening observation and help in the further processing of this material Lino.

What was your original intent? Were you trying to cleanup/purify the silver you purchased? If you were and haven't already added DMG to the entire dissolved batch of silver, then after filtering the Ag/Pd solution to separate any residuals and Au, you could drop the silver with a chloride, filter (save solution), rinse well (add to saved solution) and use your method of choice for reducing the AgCl into Ag. Then you could use a copper bar to drop the pd out of the saved solution.

or

you could use the silver nitrate/Pd nitrate solution in a small silver cell and clean up the silver that way. Again, it all depends on what your end goal was.

I have been concentrating on silver for the last 12 months and stockpiling scrap gold ready for inquarting when I am ready, and silver scrap, recovered cement and refined crystal but i and am not used to this amount of Pd.
My first step was going to be to add the shot directly into the silver cell, now I am glad I at least I did not do that, due to the amount of Pd present, if the addition of DMG is anything to go by the volume of salts produced. I had decided to go with the PD first, which I feel now was the wrong step and should have dropped the silver out as chloride first, then dealt with the Pd after the remaining gold solids were separated at filtration stage before the chloride step.

My main concern presently is whether I should add more DMG now, and hope for a better separation, or proceed and filter, then hit with DMG gain, at this stage the solution still tests pos for more dissolved Pd.
Another of my concerns is the discolouration after the last addition, going from canary yellow to darker orange yellow.

I have researched the forum and my resources and am familiarising myself with the refining of Pd salts, but my inexperience with Pd salts in this amount and concentration has caught me.

Below is the solution as it stands after 15hrs rest. I am not panicking as my metals are all still there, only I have more work in front of me now due to the overwhelming amount of Pd, it far exceeds my expectation. Up until now below in the shot of the silver cell electrolyte is the worst I have had to deal with, I am being drawn into the gravitational pull of refining, you start and keep it simple but inevitably one metal then concerns another and on it goes surprising the uninitiated with those metal types and processes, Just when you think you have it nutted out you get a surprise.

Too much Pd, poor guy... :wink:

I have limited experience with Pd and DMG, the only thing I have noticed is that it will compact over time, weeks or months, not just hours.
I would probably continue with the DMG treatment, but that's just me. I've tested several ways to separate silver and palladium but so far I don't have a solid plan or preferred method.

You could always add more water if the solution gets too thick.

The "black oxides" are probably fine gold or palladium cementing back onto the silver.

Göran

Went for it Goran and added another 8g of DMG, gave a really good stir and let it sit for an hour. I am into filtration now through Whatman no 5, bit over 2 litres to go and the filtrate is running clear, will retest again with stannous and DMG to be sure when done and try a small sample with copper plate to cement, failing that I will regretfully go to Chloride process.

Thanks to those with helpful suggestions and comments , from my perspective I tend to tread very carefully when approaching the unknown.

Edit: Filtration complete, Stannous test neg, DMG test Neg, Positive for silver, chloride formation from (Hcl)stannous test, proceeding with silver recovery.

Great!

A perfect ending on a week.

Göran

Recovery update:

611g Ag cement recovered by copper precip.
12.68g of dried DMG Pd salts.
Au is unknown and in the filter, estimate under 1g recovery, saving for AR extraction.

I am pretty happy this being my first experience with DMG and Pd salts recovery.

Well, if the salt is truly dry, you should be able to expect a little less than 4 grams pd.
Nice little bonus to your silver.