Pl atinum i s a chemical element, the chemical symbol Pt, is one of the precious metals, its element is commonly known as platinum, belonging to the platinum group element, the atomic weight of 195.078, slightly less than the atomic weight of gold, atomic number 78, belongs to transition metals. The melting point is 1772°C, the boiling point is 3827°C, and the density is 21.45g/cm3 (20°C). It is relatively soft and has good ductility, thermal conductivity and electrical conductivity. Sponge platinum is a gray sponge-like substance with a large specific surface area and strong absorption capacity for gases (especially hydrogen, oxygen and carbon monoxide). Powdered platinum black can absorb a large amount of hydrogen. The chemical properties of platinum are inactive and stable in air and humid environments. When heated below 450 °C, a platinum dioxide film is formed on the surface, which can react with sulfur, phosphorus and halogen at high temperatures. Platinum is insoluble in hydrochloric acid, sulfuric acid, nitric acid and alkali solutions, but soluble in aqua regia and molten alkali.
