ericrm,
Can we see the picture of the silver cement?
That picture looks like a bucket of mud, or one of my waste buckets, it looks like maybe some copper in there from the green oxidation, the edge of the bucket looks like some rust, the brown looks nothing like cemented silver.
Check the solution this came from you may test for values like gold in it,as depending on the source of contacts from relays gold and PGM are also a possibility, also you may have formed silver chloride, did you have powders that did not dissolve or in your filters, if the points had gold plating or PGM's the filters may have value in the powders left in them, this really depends on the source of the silver contacts though small relays possibility’s
There may be other methods to get better silver from your mud, but here is what I would try.
Here is what I think, since you had chlorides and nitric you had a form of aqua regia, this could dissolve some values, but also can cement some chlorides with the silver when you cemented with the copper, for this reason I would mix a solution of NaOH with water, do not make the caustic solution too strong.
The reason I do this is to try and make salts out of any chlorides to wash them from the silver, because silver or gold is volatile with chloride at the incinerating temperatures of these metals, my hope is to form NaCl which is water soluble, the Sodium hydroxide can also help to form oxides of some of the reactive metals at the same time.
I would do this washing with heat, to wash the mud you have, I would do this in the casserole dish with heat, lower heat and let mud settle, the liquid should clear like water and decant the salt water with a suction tool, this should help to remove salt formed from sodium hydroxide and the chlorides add water and boil lower heat decant again, leave heat on low dry powders when almost dry crush to powders again, slowly raise heat to get dry when burner on high and no more steam or smoke from powders and powders are crushed fine use your torch and incinerate them, get glowing red hot, keeping the powders stirred to get plenty of air, let them cool, now you can try it again I would wet the powders in the casserole dish with some water wash down powder from the side of the dish, before adding the diluted nitric acid to dissolve the base metals, and silver, (this time keep chlorides out of solution, use distilled water if you have city water), use heat to dissolve, let powders that do not dissolve in nitric settle well before using the suction tool to decant liquid, filtering this liquid to a clean jar, leave it to settle covered overnight (you may have powders carried over or salts settle, decant to clean jar and cement silver, if you dissolved palladium it should cement after the silver, also I would look for a thicker piece of copper, the tubing would work but with this much silver to cement you may end up adding copper metal from the pipe as it dissolves into solution.
Any powders that did not dissolve in the nitric (if enough was used to remove all of the silver), I would check for values.
