Hydrogen

IUPAC Name: Molecular hydrogen
Molecular Weight: 2.01588 [g/mol]  
Molecular Formula: H₂ 
Product Categories: refrigerants; Inorganics; Chemical Synthesis; Compressed and Liquefied GasesMicro / Nanoelectronics; Electronic Chemicals; Gases; Synthetic Reagents; Compressed and Liquefied Gases; HU - HZGas Standards; Alphabetic; H; Pure Gases; SCOTTY Gases; Hydrogen; Hydrogen; Hydrogen; Hydrogen
Stability: Stable. Highly flammable. Readily forms explosive mixtures with air. Upper (U.K.) composition limit for use of a nitrogen/hydrogen mixture in the open lab is 5.7% hydrogen.
vapor density: 0.07 (21 °C, vs air)
Water Solubility: 0.00017 g/100 mL
EINECS: 215-605-7
Color: colorless
Phase: gas
Density: 0.08988 g/L (0 °C, 101.325 kPa)
Melting point: -259.14 °C
Boiling point: -252.87 °C
Triple point: 259 °C
Critical point: 32.97 K, 1.293 MPa
Heat of fusion: (H₂) 0.117 kJ/mol
Heat of vaporization: (H₂) 0.904 kJ/mol
Specific heat capacity of Hydrogen (CAS NO.1333-74-0): (25 °C) (H₂) 28.836 J/mol/K

Hydrogen gas, H₂, was first artificially produced and formally described by T. Von Hohenheim (also known as Paracelsus, 1493–1541) via the mixing of metals with strong acids.
 In 1671, Robert Boyle rediscovered and described the reaction between iron filings and dilute acids, which results in the production of hydrogen gas. In 1766, Henry Cavendish was the first to recognize hydrogen gas as a discrete substance, by identifying the gas from a metal-acid reaction as "flammable air" and further finding in 1781 that the gas produces water when burned. In 1783, Antoine Lavoisier gave the element the name hydrogen when he and Laplace reproduced Cavendish's finding that water is produced when hydrogen is burned.
In 1898, hydrogen was liquefied for the first time by James Dewar by using regenerative cooling and his invention, the vacuum flask. He produced solid hydrogen the next year. Deuterium was discovered in December 1931 by Harold Urey, and tritium was prepared in 1934 by Ernest Rutherford, Mark Oliphant, and Paul Harteck. Heavy water was discovered by Urey's group in 1932. Fran?ois Isaac de Rivaz built the first internal combustion engine powered by a mixture of hydrogen and oxygen in 1806. Edward Daniel Clarke invented the hydrogen gas blowpipe in 1819. The D?bereiner's lamp and limelight were invented in 1823.
The first hydrogen-filled balloon was invented by Jacques Charles in 1783.
 Hydrogen provided the lift for the first reliable form of air-travel following the 1852 invention of the first hydrogen-lifted airship by Henri Giffard German count Ferdinand von Zeppelin promoted the idea of rigid airships lifted by hydrogen that later were called Zeppelins; the first of which had its maiden flight in 1900.
The first non-stop transatlantic crossing was made by the British airship R34 in 1919.
The nickel hydrogen battery was used for the first time in 1977 aboard the U.S. Navy's Navigation technology satellite-2 (NTS-2).

  Hydrogen (CAS NO.1333-74-0) is used to make other chemicals and in oxyHydrogen welding and cutting. Apart from its use as a reactant, H₂ has wide applications in physics and engineering. It is used as a shielding gas in welding methods such as atomic hydrogen welding. H₂ is used as the rotor coolant in electrical generators at power stations, because it has the highest thermal conductivity of any gas. Liquid H₂ is used in cryogenic research, including superconductivity studies.

 Hydrogen (CAS NO.1333-74-0) is primarily manufactured by steam-reforming natural gas (CH₄) or hydrocarbons (C_nH_2n+2).
 A variety of low-molecular-weight hydrocarbons can be used as feed-stock in the steam-reforming process. The reaction occurs in two separate steps: reforming and shift conversion.
 Methane:
        CH₄ + H₂O → CO + 3H₂ (reforming)
       CO + H₂O → CO₂ + H₂ (shift conversion)
 Propane:
       C₃H₈ + 3O₂ → 3CO₂ + 7H₂ (reforming)
     3CO + 3H₂O → 3CO₂ + 3H₂ (shiftconversion)
The reforming step makes a hydrogen-carbon monoxide mixture(synthesis gas) that is used to produce a variety of other chemicals.
 In the steam-reforming process, the hydrocarbon feedstock is first desulfurized by heating to 370 °C in the presence of a metallic oxide catalyst that converts the organosulfur compounds to hydrogen sulfide. Elemental sulfur can also be removed with activated carbon absorption. A caustic soda scrubber removes the hydrogen sulfide by salt formation in the basic aqueous solution.
           H₂S + 2NaO → Na₂S + 2H₂O
 Steam is added and the mixture is heated in the furnace at 760 to 980 °C and 600 psi over a nickel catalyst. When higher-molecular-weight hydrocarbons are the feedstock, potassium oxide is used along with nickel to avoid larger amounts of carbon formation.
 There are primary and secondary furnaces in some plants. Air can be added to the secondary reformers. Oxygen reacts with some of the hydrocarbon feedstock to keep the temperature high. The nitrogen or the air is utilized when it, along with the hydrogen formed, reacts in the ammonia synthesizer. More steam is added and the mixture enters the shift converter, where iron or chromic oxide catalysts at 425 °C further react the gas to hydrogen and carbon dioxide.
 Some shift converters have high- and low-temperature sections, the high-temperature section converting most of the carbon monoxide to carbon dioxide. Cooling to 38 °C is followed by carbon dioxide absorption with monoethanolamine (HOCH₂CH₂NH₂). The carbon dioxide(an important by-product) is desorbed by heating the monoethanolamine and reversing this reaction.
   HOCH₂CH₂NH₂ + CO₂ + H₂O → HOCH₂CH₂NH₃⁺HCO₃^-
Alternatively, hot carbonate solutions can replace the monoethanolamine. A methanator converts the last traces of carbon dioxide to methane, a less interfering contaminant in hydrogen used for ammonia manufacture.
 Hydrogen is also produced by an electrolytic process that produces high-purity hydrogen and consists of passing direct current through an aqueous solution of alkali, and decomposing the water.
               2H₂O → 2H₂ + O₂
A typical commercial cell electrolyzes a 15% sodium hydroxide (NaOH) solution, uses an iron cathode and a nickel-plated-iron anode, has an asbestos diaphragm separating the electrode compartments, and oper-ates at temperatures from 60 to 70 °C. The nickel plating of the anode reduces the oxygen overvoltage.
 Partial oxidation processes rank next to steam-hydrocarbon processes in the amount of hydrogen made. They can use natural gas, refinery gas, or other hydrocarbon gas mixtures as feedstocks, but their chief advantage is that they can also accept liquid hydrocarbon feedstocks such as gas oil, diesel oil, and even heavy fuel oil. All processes employ noncatalytic par-tial combustion of the hydrocarbon feed with oxygen in the presence of steam in a combustion chamber at flame temperatures between 1300 and 1500 °C. For example, with methane as the principal component of the feedstock:
           CH₄ + 2O₂ → CO₂ + 2H₂O
            CH₄ + CO₂ → 2CO + 2H₂
            CH₄ + H₂O → CO + 3H₂
The overall process is a net producer of heat; for efficient operation, heat recovery (using waste heat boilers) is important.
 Most of the hydrogen is generated on site for use by various industries, particularly the petroleum industry. Other uses include ammonia production, metallurgical industries to reduce the oxides of metals to the free metals, methanol production, and hydrogen chloride manufacture.

Reported in EPA TSCA Inventory.

Practically no toxicity except that it may asphyxiate. Highly dangerous fire and severe explosion hazard when exposed to heat, flame, or oxidizers. Flammable or explosive when mixed with air, O₂, chlorine. To fight fire, stop flow of gas.
Explodes on contact with bromine trifluoride; chlorine trifluoride; fluorine; hydrogen peroxide + catalysts; acetylene + ethylene. Explodes when heated with calcium carbonate + magnesium; 3,4-dichloronitrobenzene + catalysts; vegetable oils + catalysts; ethylene + nickel catalysts; difluorodiazene (above 90°C); 2-nitroanisole (above 250°C/34 bar + 12% catalyst); copper(II) oxide; nitryl fluoride (above 200°C); polycarbon monofluoride (above 500°C).
Forms sensitive explosive mixtures with bromine; chlorine; iodine heptafluoride (heat- or spark-sensitive); chlorine dioxide; dichlorine oxide; iodine heptafluoride (heat- or spark-sensitive); dinitrogen oxide; dinitrogen tetraoxide; oxygen (gas); 1,1,1-trisazidomethylethane + palladium catalyst. Mixtures with liquid nitrogen react with heat to form an explosive product.
Violent reaction or ignition with air + catalysts (platinum and similar metals containing adsorbed oxygen or hydrogen); bromine; iodine; dioxane + nickel; lithium; nitrogen trifluoride; oxygen difluoride; palladium + isopropyl alcohol; 3-methyl-2-penten-4-yn-1-ol; lead trifluoride; bromine fluoride (ignition on contact); nickel + oxygen; fluorine perchlorate (ignition on contact); xenon hexafluoride (violent reaction); nitrogen oxide + oxygen (ignition above 360°C); palladium powder + 2-propanol + air (spontaneous ignition); platinum catalyst; polycarbon monofluoride (ignition above 400°C).
Vigorous exothermic reaction with benzene + Raney nickel catalyst; metals (e.g., lithium; calcium; barium; strontium; sodium; potassium; above 300°C); palladium(II) oxide; palladium trifluoride; 1,1,1-tris(hydroxymethyl)nitromethane + nickel catalyst.
Hazard Codes: F+
Risk Statements: 12 
R12:Extremely flammable.
Safety Statements: 9-16-33 
S9:Keep container in a well-ventilated place. 
S16:Keep away from sources of ignition. 
S33:Take precautionary measures against static discharges.
RIDADR: UN 1950 2.1
RTECS: MW8900000
F: 4.5-31
HazardClass: 2.1

DOT Classification:  2.1; Label: Flammable Gas

  Hydrogen (CAS NO.1333-74-0), its Synonyms are Hydrogen atoms ; Molecular hydrogen ; Protium ; H . Hydrogen is a colorless, odorless gas. Hydrogen is easily ignited. Once ignited Hydrogen burns with a pale blue, almost invisible flame. The vapors are lighter than air. Hydrogen is flammable over a wide range of vapor / air concentrations. Hydrogen is not toxic but is a simple asphyxiate by the displacement of oxygen in the air. Under prolonged exposure to fire or intense heat the containers may rupture violently and rocket.