Help with a Burmese Silver Bowl

I picked up a Burmese Silver Bowl with repousse decoration of figures in landscape with buildings and the base with three fish, 16.5cm diameter, 360g / 11.59oz .
Just under £100 so not to bad,It tested for silver but had quite a lot of copper so I took it to be about 800 silver.
It had several very large cracks in it that had been repaired with lead solder.so would not have been a candidate for resale.
So I digested it and got about 300g of silver and rather a lot of rusty red goop in the bottom of my reaction chamber.
I am running the silver through my silver cell at the moment so I will not have any idea as to what was taken up with the silver for a week or two.
But the goop has given a very strong solution when processed with A.R.
I dropped the first strong batch and got a very fine black precipitate with S.M.B..so fine in fact that it ran through equiv. Whatman GF/D filter paper like it was a sieve.
Stanton test was black before dropping with a yellowish/orange hint around the sides and clean after.
So I have just had to let it settle and decant the excess fluid and put it back into A.R. to see if it will drop in a nice form when I drop it again.
But the gunk is still giving up metals into A.R. after 24hrs.(heated for four hours left over night flushed and re run-with fresh heated A.R.).
It closely resembles the silver cell slime I have been saving for later when dropped so I may just have to put them all together to pass on to some one better equipped for sorting out a jumble of platinum group metals.
Should every thing drop out of solution with S.M.B.?
It was as if I had used Ammonium Chloride instead of S.M.B The same very fine black precipitate.I was hoping to get a better separation ,I.E. positive Stanton test for P.G.M.'s after S.M.B..
Well got my gourd working ..Any ideas??

It isn't uncommon for palladium to co-precipitate with gold, and they can be difficult to separate from one another. Palladium yields a very dark brown solution (in volume), so if your solution is quite dark, you'd be well served to make a test with DMG, to determine if, perhaps, that's part of the black slimes you're reporting. That's not to say that you may not have other of the platinum group present.

When you precipitate gold from solutions that contain palladium, the gold generally comes down very dark brown, which I attributed to the co-precipitation of palladium.

Interesting piece of work, and even more interesting contents.

When you dissolved the silver, what color was the solution (before recovering the silver with copper)?

Harold

Dear Harold
The solution was quite a dark green after digestion and then went to the normal blue after dropping with copper.Having now seen your post's on Palladium contamination of silver cell's I am quite supprised at how much Palladium I may be looking at.Thanks for the hint.
And the yellow of the A.R. was much darker than I am use to seeing and not the red of a concentrated solution now you mention it.
I had not managed to get any D.M.G. yet as I only need a gram or two and I could only find it in kilo's at a time in the U.K.
I had not expected to need it yet.So have just ordered some all the way from the U.S. again.Thank Guya for cheep shipping.
I may have to back off until it arrives.this is a nice supprise and I am now looking for some other similar items to see if it is endemic of low teck third world production's
Thank you very much for your input.
Justin

While you wait for your DMG, you have other options.

Here's the deal.
When you have gold present, the reaction you get with stannous chloride for the platinum group is generally overwhelmed by the gold. So then, if you eliminate the gold, you can then test the solution with stannous, so you can, hopefully, determine what else is present. You can do that by placing a single drop of your solution in a spot plate cavity, to which you then introduce a small bit of ferrous sulfate. The ferrous sulfate must be pale green in color, not brown, otherwise it will not work. Stir the drop, ensuring that the crystal of ferrous sulfate dissolves. In the process, you should see gold forming around the crystal. When it has all been precipitated, your solution will now be a different color, although if you have an abundance of palladium in solution, that may or may not be obvious.

When you are comfortable that you have precipitated all of the gold, you can then test the solution, now free of gold chloride, for the platinum group. If the solution is quite yellow/orange in color, you may have just platinum, but if it is colored darker (leaning towards brown), palladium may overwhelm the test, so it won't be conclusive.

The description you provided of your solution speaks volumes about the possibility of the presence of both platinum and palladium. You could have tested for both once you started making a recovery of the silver, using copper, as each is slow to come down, often not happening until all of the silver is cemented. Also, when you have an abundance of these metals in solution with silver, the resulting silver cement will be off colored. The cemented platinum/palladium color the silver dark gray, so it's obvious they are present.

Do keep in mind--if you melt silver with platinum included, both will go in to solution in nitric acid, so you can expect to find them mixed. That was pretty routine for me, as I processed a lot of dental gold in my operation.

Harold

Yes I did read about testing after clearing the Au with ferrous sulfate.
but as I have only being targeting Gold and Silver I have only had the chance to do one little experiment with some silver cell slime.So I am not yet fully familiar with the procedures.
I got a nice sample after dropping with Ammonium Chloride but had not read about pressing it into a pill before melting so lost it in the flux of the bowl lining.
In fact now I have seen the symptoms I may have inadvertently destroyed a nice little Palladium chain from the second world war some time ago.
It was in with ten or fifteen silver chains and I thought it must have been stainless when it did not dissolve fully in nitric got the same dark green tho,and only slowly in A.R..
That may explain why I have not been able to get that lot of wast to form a nice single piece when I tried to smelt with flux and cast in a cone mold.I thought it was all silver chloride.
I may have to add more low melting metal to bring alloy poring point down.
Much thanks
Justin

Justin
The slimes from a silver cell are usually mainly silver and my advice is to collect them until you have at least 500 grams. If you have started messing with the slimes you will realise how much trouble they can be as they have such small particle size they stick to just about everything and anything.
Personnaly I'd leave messing with them or any PGMs they contain to a much later date as refining the PGM group is not easy and in my opinion not worth the effort unless you do it for the interest. Here in the UK we have access to cheap fast assays a reliable Pt Pd assay costs around £50-60 so save your slimes and do a recovery when volume makes it worthwhile, recover and refine any gold they contain and cement the PGMs and simply melt, add copper if you don't have a good torch or furnace, and assay and sell the resulting button, obviously the more of them you have makes the cost more worthwhile, view them as a pension pot and just keep saving them, here in the UK many 18ct white alloys contain Pd between 10-15% again many old stone set rings have Pt claws and shoulders so your hidden PGM values will slowly build to make the recovery a very pleasant and profitable process.
If you want cheap quick assays contact my friends at Guardian Laboratories who are nice lads and very helpful and not over priced.

Harold's advice is good as always so if you decide to try refining the PGMs I'd follow it the same applies if you simply want to test for their presence.

Edited for clarity..

Dear Nick
Thank you,I am doing as you say and saving all my cell slime for latter and had a feeling it might not be feasible for me to process to a good standard..
My one little test showed me just how fine and hard to handle the precipitate is.
I had thought from the rust color of the sludge left over from the Bowl that it would be mostly Au which was why I tried to process it.
from my reading I had hoped that the PGM's would have been all with the silver.I realize that was wishful thinking now.
Yet again the mental model I constructed failed to accurately mirror the real world.
Absolutely fascinating!!!And I am quite chuffed at the results a most excellent learning opportunity. I feel very privileged to have run across it.
If you could pass me the contact detail's of your friends who do reasonable priced Assay's that would be very helpful.
I will try to drop a more selective sample of Au and see if I can get any PGM separation if I can.
But I realist that any Au will have to be put in with my next Inquartation where hopefully it will be diluted enough to give a clean separation.
And hopefully add the rest to my PGM jar.But i would like to try to work out what the PGM impurity's where and how much there was as it may make for interesting item to target.
Thanks for the extra advice I had not realized that settings could differ in alloy composition that greatly,I will keep an eye out for them.
Justin

Justin the phone number and details I have posted many times but if you google the name it comes straight up but to help the phone number is 0121 359 8233.
Ask for Austin and tell him what you need and he will give you a price and any details you need to get an assay you can trust.

Aha! There's the details in the mail I lost Nick! Thanks 8)

Third Full digestion with A.R.
Recovered solution a much darker yellow than I have had before going well into orange now , Starting to get towards the brown Harold described.
The left over goop from my original silver digestion has lost it's distinctive rusty color and is now almost a white powder,it no longer reacts in cold A.R. but you get a vigorous reaction to fresh hot A.R. after 40c, I am running it at 80c at the moment and it is still going strong.
I cant wait to see how much silver cell slime I get from this batch of silver as it was very dark ,again exactly as Harold kindly described.
But am taking every step slowly as this is all new territory for me.
Thanks for all your help I would have been in quite a mess again with out your guidance.

The color I see leads me to think you have platinum, although traces of palladium could be present. If there's much palladium, the color will shift dramatically towards brown. The solution should respond quite nicely to a test with ferrous sulfate, followed by a test with stannous chloride.

Harold

Think the bowl could have been pt plated?

The Schwerter test solution went straight to work with out having filed a space.
If it had had a plating I do not think that would have been such a fast reaction.
Also the amount of impurity's I am seeing is much more than I would expect from a plated item.
I am just squeezing all the goodness I can from the sample before I go to testing.
I keep adding fresh A.R. wash to the main body of solution so will wait until I have it all reduced and nitric free before moving forward.
I was hopping that using S.M.B. would have a more selective removal of Au than ferrous sulfate for testing purposes but that was not the case at my last attempt.
I am looking forward to being able to run a number of different testing method's along side one and other when the batch is ready so will post the results to make sure I interpret them properly.
Much thanks
Justin.

300g silver from 360g initially... the suspense of what that remaining almost 2 troy ounces hold... good post, thanks for sharing!

Earlier in the thread I wondered if a specific gravity water measure, determine the density/mass of alloy, would/could have helped guide the process - and if automatically sampling a certain weight (1 ozt) to layout the remaining process would be a thrifty way dealing with unknowns, or would that just make busy work or expend more chemicals?

I am not sure what a specific gravity test would have shown,I have an idea that most of the 60g that was not silver was copper.
It is looking like I will get several grams of what ever metals are still coming out of the left over goop.
I knew that P.G.M. where meant to take longer than Au but I did not realize it could take Day's Longer.
I have been looking for the fabled Silver impurity's for some time and this is the first time I have actually found a substantial amount and not just read about it.
Earlier in the year I did have a discussion where | postulated that P.G.M.'s could be left behind after acid digestion and not be fully taken up with the silver.
Look's like it is a real possibility ,so will have to pay special attention to all my silver chloride wast as I have a feeling I have missed enough P.G.M.'s to alter the melting temperature of every thing I saved so far .

Well The left over goop is still digesting in hot fresh A.R I have a felling the A.R. is denaturing before it can full digest the metallic element.
I have stopped adding the new digestion to the the main body of fluid so I can work out if I am actually still digesting metal or making a mistake.
The test for what has all ready come off is in but are not as straight forward as I had hopped.
The test was preformed right to left.
The two far right spot test's are the recovered solution,the top one two drops of Stannous Chloride,the bottom one drop.
The bright purple in the middle is a control test with a known Au solution.
The far left starting at the top is recovered solution with Ferrous Sulphate and Stannous Chloride.
The next down is S.M.B. with Stannous Chloride.
The lowest one is a second test replicating the top most test with recovered solution ,half the amount of Ferrous Sulphate and Stannous Chloride.
So some hint's that I may have some thing other than Au but it still seems to be dropping completely with the Au.
I may have a slight Green tint to test so will wait for the D.M.G. to come and test further.

Dow.Am I a little slow or what.
I have Ruthenium.
There may be some small traces of Au,Pt,Pd, but the majority is Ru.
I will wait until the D.M.G. arrives and check buy I was not expecting any thing exotic so did not take into account the Ru goggling the other results.
Platdigger was quite correct the bowl must have had a very thick ruff platting of Ru.Looking at the pictures I can see it now ,but I questioned the piece and no other dealer would touched it as it look off .The Schwerter test was preformed on the inside of the bowl and I did not take into account the out side may have been plated so thickly,As I thought who ever has sold it had polished it up for sale and they where the same alloy.
Obviously I will not try to do much with it but I will try to get the other nicer elements out.
A quick weak A.R. instead of day's of digestion should give me a fairly good separation.
Once I have added the Ru to my P.G.M. pot seeing as it should be mostly Ag I was toying with the idea of making an anode and running it through the silver cell again.Just to try to concentrate it a bit.
Would that be a good idea or seeing as I am dealing with some elements that could produce some noctusue compounds should I just leave the hole mess for some one ells to sort out??

Justin,

Are you sure it's Ruthenium? Might it be Rhodium instead? Rhodium is often used in plating, but ruthenium doesn't seem like a good idea. If a ruthenium plated item was heated, the fumes would be highly toxic.

If you have ruthenium there, be very careful with it.

Dave

Dear Dave
Yes you have coughs yet an other world famous example of my Dyslexia.
Red result on stannous Chloride,Will not dissolve in Nitric acid and takes a disproportionately long A.R. digestion is Rh,
But my being the dippy individual I superimposed the two elements over each outer.
I do use several coping mechanisms but I still make silly errors every day and it is frustrating.But nought I can do about it.believe me I have tried but nothing short of a P.A. is effective.
Still What Gaia take's away she give's in other aria's in buckets.
Much thanks for helping me to see where I went wrong.
Last year I sold My sole to Santa and bought a very large ware house because I was horny.It is the little spelling mistakes that hurt the most.
J

Well after much messing around and making large mistake's.
I took the Gold and Rhodium mix which I had recovered and gave it a quick half strength A.R. digestion.
This yielded 0.34g of Au.
I then digested the remainder and after dropping I have 2.487 of a black powder that I believe is Rhodium.
The process took me much longer than my normal metal's as I could not filter or decant it effectively in any way.
The Au was not a problem but the Rh was so fine I had to leave it for day's to settle in the bottom of a beaker and pipette out the clear liquid from above the settled Rh.
even a small shake would disturb every thing and I would have to put it back on the shelf for an other day.
Now I have two problems is the 0.34 of Au clean enough to put in my next run as it is,I am considering cleaning it up again but it is a lot of fuss for a .3..
And now that I actually have a beaker with Rh stuck to the bottom of it what should I do with it??
I was considering trying to plate some part's for my retort stand's so they would be corrosion resistant but the only thing I have ever plated was Phone cover's so that may be a bit much for me to chew.
Has any one else got a good use for my dirty little beaker??
The weight was a ruff return as I had to zero my scales with an identical beaker to get a weight of the Rh as it is so messy to handle I have to leave it where it is.
It is such a light powder I do not think I can get it into a melting dish but I could sacrifice the beaker and use the small HO torch but that may just be a Frank Spencer Moment..