Hydrogen A colorless, odorless, flammable gas which is compressed to high pressure.
High pressure leaks frequently ignite spontaneously and burn with a colorless flame.
Hydrogen is widely used for the hydrogenation of vegetable and animal oils and fats. Hydrogen also finds wide use in the metallurgy field because of its ability to reduce metal oxides and prevent oxidation of metals in heat treating certain metals and alloys. Hydrogen finds some usage in the welding and cutting of metals. Hydrogen is extensively used in the synthesis of ammonia and in petroleum refining operations. Liquefied hydrogen has been used as a primary rocket fuel for combustion with oxygen or fluorine, and as a propellant for nuclear powered rockets and space vehicles.