Rhodium Electro-plated Metal All the jewelry which appear to be silver are made of a Rhodium-Plated Metal unless otherwise stated.
RHODIUM (Gr. rhodon, "rose"), a metallic element with the symbol Rh, is one of the transition elements in group 9 (or VIIIb) of the periodic table (see PERIODIC LAW); at.no. 45, at.wt. 102.906. Rhodium melts at about 1966° C (about 3571° F), boils at about 3727° C (about 6741° F), and has a sp.gr. of 12.4.
Rhodium was discovered in 1803 by the British chemist William Hyde Wollaston. Rhodium metal is a brilliant, silvery white, and is both hard and durable. It's insoluble in ordinary acids and is very difficult to fuse. It has a hardness rating of 4 on Moh's Hardness Scale, which maxes out at Diamond's rating of 10. The compounds of rhodium span oxidation states of 1 to 6. Aqueous solutions of many of its salts are rose colored, from which its name is derived. The metal occurs as an alloy in platinum ores, in osmiridium, and in gold-rhodium ores called rhodite. Of the elements in the crust of the earth, it ranks 81st in order of abundance.
Rhodium is used mostly as an alloy with platinum; the resulting alloy has the desirable properties of platinum and the hardness and durability of rhodium. Rhodium-platinum alloys are used in thermocouples to measure high temperatures. Pure rhodium is used as a mirror surface in searchlights and as a plating finish for jewelry and silverware. Rhodium black is a finely divided metal that contains some oxide and hydride. It is used both as a catalyst and as a black pigment for porcelain ware.
Sterling silver items with cubic zirconia are rhodium plated to prevent tarnishing, increase durability, and give it a beautiful white gold look.
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