# undesolved metalic solids after nitric acid disolution?



## Ragnor (May 21, 2017)

Hello, I dissolved some natural nuggets of unknown material in nitric acid today. One of the batches was of bright silver nuggets with a yellow/copper tint. After completely dissolving the material I had a solution which I decanted, but I also had some residue left in the bottom of the beaker. 

At the first it appeared black. But after sitting for some time I now have a deep purple colored liquid and a significant amount of shiny silver metal. 

These nuggets were collected from an area reported to have platinum present.
Is it a safe assumption the shiny silver white metal is a platinum group element?


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## kurtak (May 21, 2017)

Ragnor said:


> Hello, I dissolved some natural nuggets of unknown material in nitric acid today. One of the batches was of bright silver nuggets with a yellow/copper tint. After completely dissolving the material I had a solution which I decanted, but I also had some residue left in the bottom of the beaker.
> 
> At the first it appeared black. But after sitting for some time I now have a deep purple colored liquid and a significant amount of shiny silver metal.
> 
> ...



Per the under lined - it is NEVER "safe" to assume

Test it :!: 

By that I mean after decanting &/or filtering your solution (be "sure" you have washed out ALL the old solution - if you don't it may cause some problems in the next step)

Now take your "washed" undissolved powders & cover them with HCl depending on the amount of undissolved powder add a drop or 2 of nitric (to make AR) - apply heat - when it stops reacting take a drop of the solution & test it with stannous chloride

Stannous chloride is used to test for gold, platinum & palladium 

The other PGMs do not dissolve with AR - the exception being rhodium which is only "slightly" soluble in AR & then only if it is VERY finely divided in which case some "may" go into solution

So if it does not all dissolve with AR - it "may" be an "indication" of PGMs other then Pt or Pd - but it is still NOT "safe" to assume so - you NEED to send it out for assay to a lab qualified to test for PGMs

Kurt


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## Ragnor (May 21, 2017)

Thank you Kurt


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## Stibnut (Jun 4, 2017)

I'm having largely the same problem. Does anyone know of a reliable, cheap assayer who deals with extremely small quantities (a few g) of platinum-group metals, so that I might determine the actual composition of the insoluble residue?


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