Palladium is chemically stable, insoluble in hydrofluoric acid and resistant to phosphoric acid, perchloric acid, hydrochloric acid and cold sulfuric acid. Sodium hydroxide, sodium carbonate and sodium peroxide dissolved in aqua regia, hot concentrated sulfuric acid and concentrated nitric acid have corrosive effects on palladium. Palladium is not easy to oxidize and lose its luster at room temperature. When the temperature is about 400℃, oxides will be produced on the surface. When heated to 800℃ in room temperature air and humid environment, palladium oxide film will be formed on the surface of palladium.
Palladium has a natural pure white luster like platinum, and its color is bright. It also looks like platinum, but compared with platinum, the price of palladium is lower. Because palladium has some unique physical and chemical characteristics, it is more difficult to process jewelry than platinum, and the requirements for all links are very high.
The source of palladium
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.
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.