Graphite is an allotrope of carbon. It is a gray-black, opaque solid with stable chemical properties and corrosion resistance. It is not easy to react with acid, alkali and other agents. Natural graphite comes from graphite deposits, and can also be made from petroleum coke, asphalt coke and other raw materials through a series of processes. Graphite burns in oxygen to generate carbon dioxide, which can be oxidized by strong oxidants such as concentrated nitric acid and potassium permanganate. It can be used as antiwear agent and lubricant, and high-purity graphite can be used as neutron retarder in atomic reactors. It can also be used to manufacture crucibles, electrodes, brushes, dry batteries, graphite fibers, heat exchangers, coolers, electric arc furnaces, arc lamps, pencil refills, etc.