Platinum is a chemical element, its elemental known as platinum, belongs to the platinum element, its chemical symbol Pt, is one of the precious metals. Atomic weight 195.078, slightly less than the atomic weight of gold, atomic number 78, is a transition metal. Melting point 1772℃, boiling point 3827 ±100℃, density 21.45g/ mouth (20℃), soft, with good ductility, heat conduction and electrical conductivity. Sponge platinum is a gray spongy substance with a large specific surface area and a strong absorption capacity to gases (especially hydrogen, oxygen and carbon monoxide). The powdered platinum black absorbs a lot of hydrogen. Platinum is chemically inactive and stable in air and humidity. When heated below 450℃, the surface forms a platinum oxide film, which can react with sulfur, phosphorus and halogen at high temperature. Platinum is insoluble in hydrochloric acid, sulfuric acid, nitric acid and alkali solutions, but soluble in royal water and molten alkali. Platinum has an oxidation state of +2, +3, +4, +5, +6. Easy to form the coordination compound, such as [Pt (NH3)2] Cl2, K (Pt (NH3) Cl.
Platinum mineral containing impurities such as iron, iridium, palladium, etc., silver white or dark gray, belongs to the equiaxial crystal system, is an irregular granular or scaly aggregate with a density of 13.35~19g/cm, and is malleable. Chemical composition: Pt crystal is a natural element mineral of the isometric system. Also known as platinum, but Chinese ancient books in the so-called platinum, refers to silver, not platinum. In addition to Pt, natural platinum often contains iron and is called crude platinum ore when it reaches 9-11%. Higher is called iron and platinum ore, up to 28%. Also often contain nickel, gold, copper, palladium, iridium and rhodium, the highest palladium content can reach 21.8~30.0%, iridium 27.79~29.0.
The binary alloy containing silver based on platinum had an peritectic reaction at 1185℃ and 45%Ag. The alloy has high strength, good elasticity and low elastic aftereffect, low resistivity, low thermoelectric potential, heat resistance, corrosion resistance, no magnetism and stable performance. The smelting and processing of platinum and silver alloy are very difficult. Generally, hydrogen is used to protect the smelting in high-frequency induction heating furnace.
