Optimal Ag ratio when parting prills containing ruthenium

[Platz]

Hi, has anyone much expereince in parting fire assay prills which contain substantial amounts of ruthenium? I have had recent issues in determination of Au, Pt and Pd following a lead fire assay. The prill contains ruthenium which hinders the dissolution of the the prill with parting strength nitric acid. My typical ratio of Ag to precious metal is between 6 and 20 and even at the latter sometimes the silver does not dissolve fully resulting in cupelling again with more silver. Any advice would be much appreciated.

 

[Lou]

If there is that much ruthenium, there is also other PGM associated besides Pt and Pd if it is geologic and not an intentional concentrate from secondary man-made material. Unless the gold is high, we would switch to NiS collection as the Pb isn't even the best collector of the Ru and if there's Ru there's usually Ir and if there's Ir, you'll be stuck weighing Ir and thinking it's gold.

You should try and quantify the Ru and it seems that recupelling to lose the Ru to the slag might be the only option. You can try adding nitre at the risk of mobilizing the Pt and Pd. Ru will go first.