I bought a silver bar the other day to dissolve to make tollens reagent. I wanted to silver some glass. I made my own hno3 by using sulfuric acid and kn03. I poured a bit of the sludge and some water on the bar hoping there would be a reaction. there was none except for a dark discoloration on the bar. I don't think this is silver becuase salt would have precipitated agcl and fall to the bottom when there was no white at all in the liquid. I bought this bar on 47th street in nyc,