Palladium is one of the rarest precious metals in the world, and the element symbol Pd is one of the platinum group elements. Palladium has high purity, similar appearance to platinum, silvery white metallic luster in natural state and never fades. Palladium has high temperature resistance, corrosion resistance, wear resistance and ductility. In terms of purity, rarity and durability, platinum can be used instead, which is an ideal material for making jewelry and inlaid gems. Palladium, together with platinum, gold and silver, is one of the international precious metal spot and futures trading varieties, which was once higher than platinum in history.
In addition, palladium is also a widely used catalyst, from petrochemical industry to automobiles to watches.
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1803, British chemist wollaston discovered a new element from platinum ore. He dissolved the natural platinum ore in aqua regia, removed the acid, and added the solution of mercury cyanide (Hg(CN)2) dropwise to obtain a yellow precipitate. Sulfur, borax and this precipitate are heated together to obtain bright metal particles. He called it palladium (palladium), and the symbol of the element was Pd. The name comes from 1802, a newly discovered solar asteroid, ParaAthena, in memory of Athena, the goddess of wisdom in ancient Greek mythology.
Palladium is rare on the earth, and it is difficult to mine and smelt, which belongs to the series of rare and precious metals. The content of palladium in the earth's crust is about11×109, even only platinum 1/6, and the total annual output is less than 8% of gold. And only a few countries in the world, such as North America, Russia and South Africa, produce it. Palladium is often dispersed in various minerals (such as primary platinum ore, nickel-copper sulfide ore, nickel pyrite and so on). ) exists in alluvial deposits and placer deposits together with other platinum group elements.
Palladium is often associated with platinum, and its output is less than platinum. In mineral classification, platinum group elements belong to natural platinum subgroup, including natural element minerals such as iridium, rhodium, palladium and platinum. There is a wide range of isomorphic substitution between them, thus forming a series of isomorphic mixed crystals. These elements have great similarities in physical and chemical properties. Especially palladium and platinum, two precious metals, are very much like brothers. The metallurgical properties of these two metals are very similar, because they are also rare and have similar uses, and they often replace each other in various applications.