Testing a coin for silver

[daverino]

Given that there are a lot of silvery looking fakes out there I thought I would share a simple and non-destructive test for silver. It involves only a commercial 10K gold testing solution (dilute nitric acid) and a rubbing stone. This, a little table salt and a toothpick as well as a suspect coin are all you need (Pic 1)

I used the edge of my cracked Philip I antoninian (~30% silver) to make a light metal rubbing (pic #2) followed by one drop of the testing solution. Any metal but gold dissolves in a few seconds giving a colorless drop (pic3). The toothpick is wetted with the table salt solution and dipped in the droplet. If silver is present the droplet quickly turns milky white (pic#4)

Note 1) Duh, be careful of nitric acid. If it gets on your hands wash it off quickly or it will make your skin yellow for a while.

Note 2) The test is sensitive and you should be hardly be able to detect where you rubbed the coin. Only a very little metal is needed.

Note 3) This method is better than using a standard silver-testing solution which involves placing acid on the coin and is designed to mainly determine whether the silver is high-grade sterling or not.

[ickster]

An interesting take on an old steam engineering test. We used to take silver nitrate -which you get by adding the nitrate to the silver rubbing- then add a few drops of sample boiler water to it. If it turned milky, salt was present in the water and it couldn't be used (it would foam up when boiling).

In this case, if there is no silver, you don't get silver nitrate, and therefore no milky trace when the salt is added.