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How to Determine if Metal Is Rhodium

Rhodium is a member of the precious metals, the most valuable of all metals used for the fabrication of jewelry and other implements. Identifying rhodium from the other metals of similar appearance is a combination of how it is used and some of the physical and chemical properties. Among the properties of rhodium that distinguish it from other metals is its ability to withstand extremely high temperatures and oxidation. Some of the major industrial uses of rhodium include the formation of alloys with palladium and indium. It finds application in the production of resistant wires, electrical contacts, electrodes and furnace windings.

Things You'll Need

1 cubic millimeter of all the precious metals (Au, Ag, Pt, Pd, Ir and Rh)
Scale
Variety of concentrated acids

Instructions

- 1
  Place 1 cubic millimeter of each of the metals on the scale and record their weight to weigh the same volume of each one. Rhodium is the lightest of the six precious metals. They increase weight in the order from lightest to heaviest beginning with rhodium, palladium, silver, iridium, platinum and gold.
- 2
  Drop the metal sample in a small beaker containing a small volume of concentrated acid to test it. Arrange a series of beakers with 10 ml of concentrated acid. Use the acids commonly used to dissolve metals, namely hydrochloric acid, nitric acid, sulfuric acid, aqua regia (mixture of hydrochloric and nitric acids) and hydrofluoric acid. Place the metal in each of the beakers and watch for any reaction. Of all the precious metals, rhodium is the only one that does not react with any of the acids. All of the other metals will react with at least one of the acids.
- 3
  Determine how the metal is used, particularly in making jewelry. Common silver colored metals used for jewelry are white gold, platinum and silver. Plating rhodium over these metals provides a surface that is brilliant and lustrous but does not tarnish due to its high resistance to oxidation.

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