Buying Sterling? Yes, No, Maybe?

Oh, OK. Something more like a "spot test" then. Yes, those have their uses but accuracy of analysis usually is not one of them.



What, no pocket model Atomic Absorption Spectrophotometer?



Yes, that is a valid point. Another valid point is that "sterling silver" is defined as being 92.5% silver, so anything that assays as less than that in silver content can still be silver but it cannot be sterling silver.

The problem with the spot tests is that they are decent at telling you WHAT is there but not very good at telling you HOW MUCH is there.

There are optical tests wherein either a color or a turbidity is developed by the test. In those cases, a comparator (small box with 2 viewing holes and a movable disk containing reference windows of a specific color or darkness). A control is put in one tube while a test sample goes in the other. The disk is then rotated until the control and test windows look the same. These aren't too bad, actually, but they usually require that a small sample be removed from the material to be tested. If often doesn't have to be very much but most sellers do not want even small chunks of material removed from whatever it is that they are selling. Maybe what we need is a good / cheap tricorder?

That would be good. There is a good manufacturing practices set of standards called "ISO 9000". Any company that manufactures and wants to export or sell to a company that exports is well advised to meet whatever ISO 9000 standards apply to their industry. Very tight product purity specs are one of the requirements for meeting these standards. Some companies proudly declare their ISO 9000 compatibility on their web site home page and in their product literature. It has become quite a competitive issue in some industries. Don't know how the PM business relates to this but it would be good if they were standardized as to product descriptions and purity.

I don't have the exact information in front of me but here's what I do have. The FTC, which I'm assuming is the federal trade commission, regulates gold & silver purity. It's my understanding that purity is now supposed to be within 4 parts per thousand, with 10 parts per thousand variance allowed if the item has been soldered. Prior to when this legislation came out variances were allowed to be greater. On a side note, in the US it has to be at least 10k to be called gold, while in some other countries they use 8k or 9k in some jewelry.

If you have 14k that tests as 12k one of a number of things could be happening. Your test equipment could be off. The item could have been made prior to the newest regulations. The manufacturer could have cheated. Do a web search for under karated gold....there are several articles out there by various jewelers groups with examples of sellers of underkarated gold. I use an electronic gold tester & have run across items that were underkarated.

Here's a link:

http://www.ftc.gov/bcp/guides/jewel-gd.shtm