Molybdenum disulfide (or moly) is an inorganic compound composed of molybdenum and sulfur. These elements include vanadium, manganese, iron, cobalt, copper, zinc, selenium, strontium and molybdenum. Chromium, vanadium, molybdenum, and tungsten increase strength by forming second-phase carbides. Nitriding alloys are alloy steels with nitride-forming elements such as aluminum, chromium, molybdenum and titanium. The principal ores of copper, zinc, nickel, cobalt, molybdenum, and other metals are sulfides. However, during tempering, elements like chromium, vanadium, and molybdenum precipitate with the carbon. CVD for molybdenum, tantalum, titanium, nickel is widely used. Natural resources of the republic include iron ore, diamonds, vanadium, molybdenum, and others. These enzymes contain iron, often with a second metal, usually molybdenum but sometimes vanadium. Some widely used promoters are zinc, molybdenum and chromium. The hydrodesulfurization of petroleum uses a catalyst derived from cobalt and molybdenum. The anode is usually made out of tungsten or molybdenum. Commercial catalysts are often based on molybdenum and ruthenium. Gold, silver, molybdenum, and sulphuric acid are all removed from copper ore during processing. Usual grid materials are copper, molybdenum, gold or platinum.