We tried to analyze a few silver items (800/1000 fineness) using a hand-held ED-XRF spectrometer, which is normally used for analyzing industrial alloys etc. The operating element range of the device was Mg-U.
The most surprising result of the experiment was a very high reported content of potassium, often higher than silver. For example, one of results (listing just elements with content >= 1%):
| element | content |
|-----------------------------------|---------|
| K | 36.0% |
| Ag | 27.5% |
| (sum of elements lighter than Mg) | 24.7% |
| Cu | 5.0% |
| Sn | 4.5% |
Such high potassium content was pretty consistent across all our silver samples, but not present in others (like stainless steel)
Clearly it's not possible that the alloy could contain that much potassium. Where could this result come from? Can potassium be somehow bound to the molecules at the thin surface layer? Or is there some explanation for this phenomenon?