In 1803 rhodium was discovered by William Hyde Wollaston in a South American piece of platinum ore.
He chose the name rhodium after the Greek rhodeos (rose red) because many compounds with rhodium showed this colouring. The new metal was subsequently used in 1820 as the tip of pens in a rhodium-tin alloy. Rhodium is one of the rarest non-radioactive metals in the earth's crust. It is found in Goodnews Bay in Alaska and in Stillwater, Montana. It is found in their ores together with platinum and gold, among others. Rhodium extraction, like the extraction of platinum metals in general, is extremely costly. Due to their great similarity, they are very difficult to extract from one another. In addition to the most important area of application, the production of catalysts, rhodium is also used in the jewellery industry to refine surfaces. Here, it takes on the task of tarnish protection, especially for silver and white gold alloys.
What is rhodium?
Rhodium is a silvery-white, rare precious metal from the platinum group. It is particularly hard, lustrous and corrosion resistant, which is why it is often used in the jewelry and watch industries for gold plating jewelry and watches. Rhodium also has applications in the automotive industry as a catalyst carrier, in the electronics industry, and in the chemical industry as a catalyst for the production of chemical products. It is one of the most expensive metals and is usually extracted as a companion product in the mining of platinum and palladium.
How is rhodium extracted?
Rhodium is mostly extracted as a by-product in the mining of platinum and palladium. Smelting of the ore results in the separation of the various metals, including rhodium. It can also be recovered from spent catalysts, which are removed after use in the automotive and petrochemical industries. There are also smaller deposits of rhodium that can be mined directly. The extraction of rhodium requires a high level of expertise and specialized equipment.
What are the special properties of rhodium?
Rhodium has the following special properties:
- Highly reflective: Rhodium has very high reflectivity, which makes it attractive for applications in optics.
- Corrosion Resistant: Rhodium is extremely corrosion resistant and withstands aggressive acid and base contact.
- High Temperature Resistant: Rhodium can withstand high temperatures, making it suitable for electrical engineering applications.
- Difficult to Melt: Rhodium has a high melting point, making it difficult to machine.
- Rare: Rhodium is one of the rarest elements and has a high value, making it a valuable raw material for many applications.
What role does rhodium play in the jewelry industry?
Rhodium is popular in the jewelry industry because of its hardness, luster and corrosion resistance. It is often applied to jewelry to increase its durability and longevity and protect it from wear and tear. In addition, rhodium is a very white metal that imparts a particularly bright luster, so it is often applied to jewelry made of white gold to enhance its color. It is a sought-after plating for rings, earrings, necklaces and other jewelry.
How is this rhodium applied to jewelry? Does it not wear off quickly?
Rhodium is applied to jewelry by electroplating. In this process, the jewelry is immersed in a solution containing rhodium and electrically charged. This results in the deposition of rhodium on the surface of the jewelry.
Rhodium has high corrosion resistance and good resistance to wear, so it usually does not wear off quickly. However, it can wear off under certain conditions and through frequent contact with other materials and substances such as lotions, perfumes, or chemicals. For this reason, jewelry plated with rhodium must occasionally be re-plated to maintain its original beauty and brightness.
