You can test gold, platinum, and palladium jewelry to determine if an unmarked piece you've acquired is genuine. There are easy ways to test jewelry yourself and thus eliminate the need for a professional appraisal. By using chemical agents, namely acids, it's simple to gauge a reaction for a particular precious metal. Always use protective, disposable latex gloves, or if allergic, non-latex gloves, in case of spills.
Examine your jewelry for any marks before testing. Use a regular magnifying glass or a professional eye magnifying tool to look your piece over. Ten-karat gold is marked 10k, 16, 417, or 10KP; 14-karat gold is marked 583, 585, or 14KP; 18-karat gold is marked 750 or 18KP; 22-karat gold is marked 916 or 917; and pure gold, 24 karat, is marked 999. Marked platinum will say 900 Plat, Plat 900, Pt900, or 900Pt. Modern palladium is usually marked Pd950. If you can't find a mark, you'll have to test the piece.
To test for gold, purchase nitric acid. You can obtain this solution, along with other acids for jewelry testing, from a jewelry-supply company (many can be found online).
Wearing disposable gloves, follow the directions on the test kit. Typically, you'll rub the gold onto a piece of stone, then apply the nitric acid to the stone over the rub mark. The acid will dissolve onto the stone and completely dissipate when it's not genuine gold. Any color change, though, indicates gold. The lighter the color change the higher the karat weight. A darker color change can indicate 14k gold or less.
To test for platinum, use a magnet. This is the simplest way to test platinum jewelry without causative acids. If the magnet sticks, there is iron in the piece, and the piece is not pure. Other tests for platinum are the scratch-test method (similar to the one for gold); a melting-point test that looks for tarnish when flame is applied to the metal; and a density test, which involves weighing the platinum. Both the melting-point test and the density test are best done by professionals with the proper equipment.
To test palladium, first make sure your piece is not platinum. Weigh the piece—this is the easiest way to determine that palladium is not platinum. Most palladium is lighter than platinum. Pure palladium is rare in vintage jewelry because it was used only as a filler metal for other jewelry. Modern palladium is 12 percent lighter than platinum and more durable. A professional density-weight test may be required for palladium.