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Shielding gas: Hydrogen is used as a shielding gas in welding methods such as atomic hydrogen welding. [167] [168] Cryogenic research: Liquid H 2 is used in cryogenic research, including superconductivity studies. [169] Leak detection: Pure or mixed with nitrogen (sometimes called forming gas), hydrogen is a tracer gas for detection of minute
Hydrogen gas is produced by several industrial methods. [1] Nearly all of the world's current supply of hydrogen is created from fossil fuels. [2] [3] Most hydrogen is gray hydrogen made through steam methane reforming. In this process, hydrogen is produced from a chemical reaction between steam and methane, the main component of natural gas.
For hydrogenation, the obvious source of hydrogen is H 2 gas itself, which is typically available commercially within the storage medium of a pressurized cylinder. The hydrogenation process often uses greater than 1 atmosphere of H 2 , usually conveyed from the cylinders and sometimes augmented by "booster pumps".
Natural hydrogen is generated from various sources. Many hydrogen emergences have been identified on mid-ocean ridges. [22] Serpentinisation occurs frequently in the oceanic crust; many targets for exploration include portions of oceanic crust which have been obducted and incorporated into continental crust.
1809 – Gay-Lussac's law, a gas law relating temperature and pressure. 1811 – Avogadro's law, a gas law relating volume and amount of substance. 1819 – Edward Daniel Clarke invents the hydrogen gas blowpipe. 1820 – W. Cecil writes a letter, "On the application of hydrogen gas to produce a moving power in machinery". [6] [7]
Compressed hydrogen is a storage form whereby hydrogen gas is kept under pressures to increase the storage density. Compressed hydrogen in hydrogen tanks at 350 bar (5,000 psi) and 700 bar (10,000 psi) are used for hydrogen tank systems in vehicles, based on type IV carbon-composite technology.
Forming gas is a mixture of hydrogen (mole fraction varies) [1] and nitrogen. It is sometimes called a "dissociated ammonia atmosphere" due to the reaction which generates it: 2 NH 3 → 3 H 2 + N 2. It can also be manufactured by thermal cracking of ammonia, in an ammonia cracker or forming gas generator. [2]
Hydrogen is a common and easy to find element, given that each molecule of water has two atoms of hydrogen for every oxygen atom present. [10] Hydrogen can be separated from water via several means, including steam reforming (normally involving the use of fossil fuels) and electrolysis (which requires large amounts of electricity and is less commonly used).