A positive, non-destructive test for Platinotypes - by Mike Ware.
Place a tiny drop of hydrogen peroxide solution on a dark region of the print.
(The hydrogen peroxide should be the ordinary domestic variety, so-called
'10-' or '20-volume', i.e. 3% to 6%.)
If the print contains a significant amount of platinum, the clear drop will
turn white within a few seconds with minute bubbles of gas (oxygen) and may
even effervesce ('fizz'). The platinum is unaffected, because this is a
catalytic decomposition of hydrogen peroxide:
2H2O2 -> O2 + 2H2O
The only products are harmless to the print - oxygen and water. Mop up the
liquid with a cotton bud, and there will be no trace. The test can be
conducted on a very small scale if you use a lens.
With palladium nothing happens, so you can identify all those palladium
prints lurking out there, that are masquerading as platinotypes.
With pure silver prints there is also no reaction; but if the print
contains iron(III) impurity then you may get effervescence *and bleaching*
of the silver. A drop of H2O2 placed in a clear, highlight region may also
effervesce if much iron(III) is present.
Although this test is 'non-destructive' to pure platinum, palladium and
silver prints, I cannot guarantee what might happen with more exotic
processes, e.g. gum-platinum, but these should be obvious anyway. Don't try
it out on your Stieglitz's just yet.
Mike
PS. I will be away for a week, before I can field any responses to this.