ar with formic acid

[arthur kierski]

after eliminating base metals with nitric acid,i am left with a powder containing gold and pd-----just to avoid questions that the nitric dissolves pd,i tell you all, that pd is dissolved in the nitric but not totally---this powder (au+pd) is dissolved in ar and precipitated with formic acid at ph6----the result is a beautiful mix of gold +pd-------
when i redissolve this mix with ar (for the second time) one should expect total dissolution,but a grey powder stays in the botton of the becker-----what could be this grey metal powder? ag?pdo?-------thanks for coments
Arthur

 

[jimdoc]

What was it you started with?

 

[arthur kierski]

i started with black chips ,solder ,smds----------before what i wrote in the previous thread,i eliminated the tin and lead with hcl boil for hours and with boiling water to eliminate the lead chloride------

 

[samuel-a]

that's a long shot, but, might be ruthenium

 

[4metals]

quite possibly it is PdO which does not dissolve in Aqua regia. However it does decompose at 750 C so roasting it will convert it to Pd metal. Now if it dissolves in Nitric you can limit the possibilities. A quick test with DMG will identify it for sure when it's in solution.