Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. The water-gas shift reaction (WGS/Dussan Reaction) is a chemical reaction in which carbon monoxide reacts with water vapor to form carbon dioxide and hydrogen: CO + H2O CO2 + H2. The water-gas shift reaction is an important industrial reaction. It is often used in conjunction with steam reforming of methane or other hydrocarbons, which is important for the production of high purity hydrogen for use in ammonia synthesis. The water-gas shift reaction was discovered by Italian physicist Felice Fontana in 1780. The reaction is slightly exothermic, yielding 42 kJ (10 kcal) per mole.