The ruthenium is one of the platinum group metals and is silver white. The melting point is 2310°C and it is a refractory metal. The density is 12.2 g/cm3.钌 At moderate temperatures, the chemical properties are stable, but when the temperature rises above 450°C in air, helium will slowly oxidize to generate volatile yttrium oxide, which is the same toxic substance as yttrium oxide. The aqua regia, sulfuric acid, hydrochloric acid, and phosphoric acid at 100°C do not erode helium, but at the same temperature, potassium cyanide solution and mercuric chloride solution can significantly erode helium. At 300°C, fluorine reacts with hydrazine to form RuF5. Hard and brittle, it is difficult to process. The use of niobium and its alloys are mainly used as catalysts in the petrochemical industry. Anode coatings are available in the electrical and electronics industry. Titanium anodes coated with platinum and platinum have replaced graphite anodes in electrolytic cells, increasing efficiency and extending electrode life. Antimony can be used to make wear-resistant hard alloys. The platinum-iridium alloy can be used to color the spark plug of an aircraft engine, and can be used as a container lining for manufacturing optical glass.