PRODUCTS

E949 HYDROGEN

E949 Hydrogen is used to make other chemicals and in oxyHydrogen welding and cutting.
E949 Hydrogen is used mixtures N2-H2 or Ar-H2 for cutting and welding of stainless steel.
E949 Hydrogen is used pure hydrogen or mixtures N2-H2 or Ar-H2 for heat treatment in a controlled atmosphere, blank glowing, soldering in the oven.

CAS number: 1333-74-0
EC number: 215-605-7
Molecular formula: h₂
Molecular weight: 2.016 g/mol

SYNONYMS:
Hydrogen, Molecular hydrogen, Dihydrogen, 1333-74-0, Protium, hydrogen-1, DTXSID9029643, 7YNJ3PO35Z, CHEBI:18276, Hydrogen atoms, RefChem:389053, DTXCID00196437, 215-605-7, H, Atomic hydrogen, Hydrogen gas, H2, Hydrogen in Steel, 1g/piece, 1-Butanol, titanium(4+) salt, monohydrate, homopolymer (9CI), Hydrogen, atomic, H in Stainless Steel, 1g Balls of O 6.35 mm, hidrogeno, hydrogene, Wasserstoff, o-Hydrogen, p-Hydrogen, hydrogen molecule, monoatomic hydrogen, HYDROGEN [HSDB], HYDROGEN [MI], T101 Monoclonal Antibody, HYDROGEN [WHO-DD], Hydrogen in stainless steel, Hydrogen, >=99.99%, Hydrogen, >=99.999%, SCHEMBL29349524, SCHEMBL29357126, CHEBI:18140, CHEBI:33251, YZCKVEUIGOORGS-UHFFFAOYSA-N, NSC356464, AKOS016038407, Hydrogen in Steel, 1g/ball, 20 pcs, NSC-356464, UN 1049, UN 1966, E949, Hydrogen, Messer(R) CANgas, 99.999%, E 949, E-949, NS00080750, C00282, H in Stainless Steel, 1g Stick of O 3.8x12 mm, H in Stainless Steel, 1g Stick of O 4.1x10 mm, Q3027893, Hydrogen in Aluminum, 10 rods 0.5" diameter x 24", 12184-90-6, 1H, H-H, Hydrogen, Molecular Hydrogen, Dihydrogen, Hydrogen Gas, Gaseous Hydrogen, H₂, Compressed Hydrogen, Refrigerated Liquid Hydrogen, Atomic Hydrogen, Elemental Hydrogen, Fuel Hydrogen, Industrial Hydrogen, Food Grade Hydrogen, Ultra Pure Hydrogen, Hydrogen Molecule

E949 Hydrogen is a colorless, odorless gas.
E949 Hydrogen is easily ignited.
Once ignited E949 Hydrogen burns with a pale blue, almost invisible flame.

The vapors of E949 Hydrogen are lighter than air.
E949 Hydrogen is not toxic but is a simple asphyxiate by the displacement of oxygen in the air.
E949 Hydrogen, refrigerated liquid (cryogenic liquid) appears as a colorless very cold liquid shipped in special heavily insulated containers.

E949 Hydrogen boils at -442 °F.
E949 Hydrogen gas at normal temperatures is lighter than air but until vapors boiling off from the liquid warm up they are heavier than air.
E949 Hydrogen is very easily ignited.

E949 Hydrogenurns with a pale blue, almost invisible flame.
E949 Hydrogen is a leak could be either a vapor or a liquid leak.
The container of E949 Hydrogen is designed to vent the vapor as it is boils off.

DiHydrogen is an elemental molecule consisting of two E949 Hydrogens joined by a single bond.
E949 Hydrogen has a role as an electron donor, an antioxidant, a fuel, a human metabolite and a member of food packaging gas.
It is a gas molecular entity, an elemental molecule and an elemental E949 Hydrogen.

E949 Hydrogen is the lightest and simplest gas, used in the food industry mainly as a protective packaging.
Thanks to its unique properties, such as the absence of color, taste and odor, E949 Hydrogen can effectively extend the shelf life of food products without affecting their sensory quality.

The use of E949 Hydrogen in packaging technology helps prevent oxidation and spoilage processes, which is key to preserving the freshness and nutritional value of food.
E949 Hydrogen is a very low-density gas, which makes lightweight protective packaging possible.

Its negligible chemical reactivity under typical conditions makes it safe for food contact, provided it is properly used and safety standards are followed.
Dihydrogen is an elemental molecule consisting of two E949 Hydrogens joined by a single bond.
E949 Hydrogen has a role as an electron donor, an antioxidant, a fuel, a human metabolite and a member of food packaging gas.

It is a gas molecular entity, an elemental molecule and an elemental E949 Hydrogen.
E949 Hydrogen is under investigation in clinical trial NCT02830854 (Molecular E949 Hydrogen for Cognitive Function and Performance in Elderly).
E949 Hydrogen is the first chemical element in the periodic table with atomic symbol H, and atomic number 1.
Protium (atomic weight 1) is by far the most common E949 Hydrogen isotope.

E949 Hydrogen also exists as the stable isotope DEUTERIUM (atomic weight 2) and the radioactive isotope TRITIUM (atomic weight 3).
E949 Hydrogen forms into a diatomic molecule at room temperature and appears as a highly flammable colorless and odorless gas.

The food additive E949, known as E949 Hydrogen, is an odorless, colorless, and highly flammable gas used primarily as a propellant and packaging gas in the food industry.
Its origin is inorganic and E949 Hydrogen is industrially obtained through water electrolysis, natural gas reforming, or biomass gasification.

E949 Hydrogen is the lightest and most abundant element in the universe, but on Earth it is mainly found combined in compounds such as water.
E949 Hydrogen's physicochemical properties include very low density (0.0899 g/L at 0°C), boiling point of -252.9°C, and very low solubility in water.

As a propellant, E949 Hydrogen is used to create modified atmospheres in packaging, preventing oxidation and microbial growth, and as a propellant in food aerosols.
The history of E949 Hydrogen as an additive dates back to its approval in the European Union, where it was evaluated by EFSA (European Food Safety Authority) and WHO (World Health Organization).

The overall safety assessment is very high, and it must be labeled as "E949 Hydrogen" or "E949" in the ingredient list.
It is important to note that E949 Hydrogen is not metabolized in the human body and is eliminated unchanged, contributing to its safety profile.
E949 Hydrogen is a colourless and odourless gas.

The gas is highly flammable and explosive.
Also the hardening (E949 Hydrogenation) of vegetable and animal oils and fats is carried out with E949 Hydrogen.
E949 Hydrogen belongs to the class of inorganic compounds known as other non-metal hydrides.
These are inorganic compounds in which the heaviest atom bonded to an E949 Hydrogen atom belongs to the class of 'other non-metals'.

E949 Hydrogen, typically nonmetallic except under extreme pressure, readily forms covalent bonds with most nonmetals, contributing to the formation of compounds like water and various organic substances.
E949 Hydrogen's role is crucial in acid–base reactions, which mainly involve proton exchange among soluble molecules.
In ionic compounds, E949 Hydrogen can take the form of either a negatively-charged anion, where it is known as hydride, or as a positively charged cation, H+, hydron.

Although tightly bonded to water molecules, hydrons strongly affect the behavior of aqueous solutions, as reflected in the importance of pH.
Hydride, on the other hand, is rarely observed because it tends to deprotonate solvents, yielding E949 Hydrogen.

In the early universe, neutral E949 Hydrogen atoms formed about 370,000 years after the Big Bang as the universe expanded and plasma had cooled enough for electrons to remain bound to protons.
After stars began to form, most of the E949 Hydrogen in the intergalactic medium was re-ionized.

Nearly all E949 Hydrogen production is done by transforming fossil fuels, particularly steam reforming of natural gas.
E949 Hydrogen can also be produced from water or saline by electrolysis, but this process is more expensive.
E949 Hydrogen's main industrial uses include fossil fuel processing and ammonia production for fertilizer.
Emerging uses for E949 Hydrogen include the use of fuel cells to generate electricity.

USES and APPLICATIONS of E949 HYDROGEN:
E949 Hydrogen is used to make other chemicals and in oxyHydrogen welding and cutting.
E949 Hydrogen is used mixtures N2-H2 or Ar-H2 for cutting and welding of stainless steel.
E949 Hydrogen is used pure hydrogen or mixtures N2-H2 or Ar-H2 for heat treatment in a controlled atmosphere, blank glowing, soldering in the oven.

E949 Hydrogen is used powder metallurgy, sintering, manufacture of pseudo alloys.
E949 Hydrogen is used fuel cells, Hardening of oils and fats, Manufacture of semi-conductors and precious stones, Carrier gas for analysis equipment, Cutting and melting of glass objects, Hydro-oxygen cutting of thick steel, Under water cutting with hydro-oxygen burner.

E949 Hydrogen is used to reducing gas for the protection of welds on steel, stainless steel, copper...
E949 Hydrogen is used welding of lead, Filling gas for alternators, Reducing gas in the chemistry and metallurgy, Gas detection equipment, Soldering of precious metals and non-ferro alloys.

E949 Hydrogen is used in the packaging of a variety of food products, including fatty fish, meats, and some types of cheese, where it helps preserve product quality by preventing fat oxidation.
E949 Hydrogen is also used in the production of certain types of beverages, where it acts as a reducing agent.

Uses of E949 Hydrogen: Hydrogenation of oils like soybean, corn and cottonseed
Other Uses of E949 Hydrogen: Production of sorbitol used in cosmetics
E949 Hydrogen is produced in chemical plants and is used for the heat treatment and protection against oxidation of metal.

E949 Hydrogen is a food additive used as a packaging gas.
E949 Hydrogen has the basis of the gas H2.
E949 Hydrogen is used for technological effect rather than nutritional value.

E949 Hydrogen is rarely used and only in special technological cases.
In production, E949 Hydrogen helps manage appearance, sweetness, aroma, foaming, texture, packaging environment, or dough behavior.

In home cooking, such tasks are often unnecessary: E949 Hydrogen can be eaten fresh, prepared in small portions, or made with simple ingredients.
In industrial food, E949 Hydrogen helps withstand storage, transportation, and achieve consistent results.

-Petrochemical industry uses of E949 Hydrogen:
Large quantities of E949 Hydrogen are used in the "upgrading" of fossil fuels.
Key consumers of E949 Hydrogen include hydrodesulfurization and hydrocracking.
Many of these reactions can be classified as E949 Hydrogenolysis, i.e., the cleavage of bonds by E949 Hydrogen.
Illustrative is the separation of sulfur from liquid fossil fuels:
R2S + 2 H2 → H2S + 2 RH

-Hydrogenation uses of E949 Hydrogen:
Hydrogenation, the addition of E949 Hydrogen to various substrates, is done on a large scale.
Hydrogenation of N2 produces ammonia by the Haber process:
N2 + 3 H2 → 2 NH3

This process consumes a few percent of the energy budget in the entire industry and is the biggest consumer of E949 Hydrogen.
The resulting ammonia is used extensively in fertilizer production.
These fertilizers have become essential feedstocks in modern agriculture.

Hydrogenation is also used to convert unsaturated fats and oils to saturated fats and oils.
The major application is the production of margarine.
Methanol is produced by E949 Hydrogenation of carbon dioxide.

The mixture of E949 Hydrogen and carbon dioxide used for this process is known as syngas.
It is similarly the source of E949 Hydrogen in the manufacture of hydrochloric acid.
E949 Hydrogen is also used as a reducing agent for the conversion of some ores to the metals.

-Fuel uses of E949 Hydrogen:
The potential for using E949 Hydrogen (H2) as a fuel has been widely discussed.
E949 Hydrogen can be used in fuel cells to produce electricity, or burned to generate heat.
When E949 Hydrogen is consumed in fuel cells, the only emission at the point of use is water vapor.

When burned, E949 Hydrogen produces relatively little pollution at the point of combustion, but can lead to thermal formation of harmful nitrogen oxides.
If E949 Hydrogen is produced with low or zero greenhouse gas emissions (green E949 Hydrogen), it can play a significant role in decarbonizing energy systems where there are challenges and limitations to replacing fossil fuels with direct use of electricity.

E949 Hydrogen fuel can produce the intense heat required for industrial production of steel, cement, glass, and chemicals, thus contributing to the decarbonization of industry alongside other technologies, such as electric arc furnaces for steelmaking.
However, it is likely to play a larger role in providing industrial feedstock for cleaner production of ammonia and organic chemicals.

For example, in steelmaking, E949 Hydrogen could function as a clean fuel and also as a low-carbon catalyst, replacing coal-derived coke (carbon):
2FeO + C → 2Fe + CO2
vs
FeO + H2 → Fe + H2O

E949 Hydrogen used to decarbonize transportation is likely to find its largest applications in shipping, aviation and, to a lesser extent, heavy goods vehicles, through the use of E949 Hydrogen-derived synthetic fuels such as ammonia and methanol and fuel cell technology.

For light-duty vehicles including cars, E949 Hydrogen is far behind other alternative fuel vehicles, especially compared with the rate of adoption of battery electric vehicles, and may not play a significant role in future.
Liquid E949 Hydrogen and liquid oxygen together serve as cryogenic propellants in liquid-propellant rockets, as in the Space Shuttle main engines.

NASA has investigated the use of rocket propellant made from atomic E949 Hydrogen, boron or carbon that is frozen into solid molecular E949 Hydrogen particles suspended in liquid helium.
Upon warming, the mixture vaporizes to allow the atomic species to recombine, heating the mixture to high temperature.
E949 Hydrogen produced when there is a surplus of variable renewable electricity could in principle be stored and later used to generate heat or to re-generate electricity.

It can be further transformed into synthetic fuels such as ammonia and methanol.
Disadvantages of E949 Hydrogen fuel include high costs of storage and distribution due to E949 Hydrogen's explosivity, its large volume compared to other fuels, and its tendency to embrittle materials.

-Nickel–E949 Hydrogen battery uses:
The very long-lived, rechargeable nickel–E949 Hydrogen battery developed for satellite power systems uses pressurized gaseous H2.
The International Space Station, Mars Odyssey and the Mars Global Surveyor are equipped with nickel-E949 Hydrogen batteries.
In the dark part of its orbit, the Hubble Space Telescope is also powered by nickel-E949 Hydrogen batteries, which were finally replaced in May 2009, more than 19 years after launch and 13 years beyond their design life.

-Semiconductor industry uses of E949 Hydrogen:
E949 Hydrogen is employed in semiconductor manufacturing to saturate broken ("dangling") bonds of amorphous silicon and amorphous carbon, which helps in stabilizing the materials' properties.
E949 Hydrogen, introduced as an unintended side-effect of production, acts as a shallow electron donor leading to n-type conductivity in ZnO, with important uses in transducers and phosphors.
Detailed analysis of ZnO and of MgO shows evidence of four and six-fold E949 Hydrogen multicentre bonds.
The doping behavior of E949 Hydrogen varies with material

-Niche and evolving uses of E949 Hydrogen:
Beyond than the uses mentioned above, E949 Hydrogen is used in smaller scales in the following applications:
Shielding gas:
E949 Hydrogen is used as a shielding gas in welding methods such as atomic E949 Hydrogen welding.

Coolant:
E949 Hydrogen is used as a coolant in large electrical generators due to its high thermal conductivity and low density.
The first E949 Hydrogen-cooled turbogenerator went into service using gaseous E949 Hydrogen as a coolant in the rotor and the stator in 1937 in Dayton, Ohio.

Cryogenic research:
Liquid H2 is used in cryogenic research, including superconductivity studies.

Food industry:
E949 Hydrogen is an authorized food additive (E949) that is used as a packaging gas, and also has antioxidant properties.

Leak detection:
Pure or mixed with nitrogen (sometimes called forming gas), E949 Hydrogen is a tracer gas for detection of minute leaks.
Applications can be found in the automotive, chemical, power generation, aerospace, and telecommunications industries; it also allows for leak testing in food packaging.

Neutron moderation:
Deuterium (E949 Hydrogen-2) is used in nuclear fission applications as a moderator to slow neutrons.

Nuclear fusion fuel:
Deuterium is used in nuclear fusion reactions.

Isotopic labeling:
Deuterium compounds have applications in chemistry and biology in studies of isotope effects on reaction rates.

Tritium uses:
Tritium (E949 Hydrogen-3), produced in nuclear reactors, is used in the production of E949 Hydrogen bombs, as an isotopic label in the biosciences, and as a source of beta radiation in radioluminescent paint for instrument dials and emergency signage

PROPERTIES of E949 HYDROGEN:
Atomic E949 Hydrogen
Electron energy levels
The ground state energy level of the electron in a E949 Hydrogen atom is −13.6 electronvolts (eV), equivalent to an ultraviolet photon of roughly 91 nanometers wavelength.
The energy levels of E949 Hydrogen are referred to by consecutive quantum numbers, with n=1 being the ground state.

The E949 Hydrogen spectral series corresponds to emission of light due to transitions from higher to lower energy levels.
Each energy level is further split by spin interactions between the electron and proton into four hyperfine levels.
High-precision values for the E949 Hydrogen atom energy levels are required for definitions of physical constants.

Quantum calculations have identified nine contributions to the energy levels.
The eigenvalue from the Dirac equation is the largest contribution.
Other terms include relativistic recoil, the self-energy, and the vacuum polarization terms.

NOMENCLATURE of E949 HYDROGEN:
The standards organization for chemical names, IUPAC, gives general names when the context assumes natural isotope abundance or ignores the isotope.
These general names are E949 Hydrogen for the neutral atom, hydron for the cation, H+, hydride for the anion, and H-.
The name proton is often used for the positively charged cation, but this is strictly correct only for the cation of the dominant isotope 1H.

SOURCE of E949 HYDROGEN:
E949 Hydrogen is an inorganic chemical element — it is not derived from any animal, plant, or biological source.
For industrial and food-grade applications, E949 Hydrogen is typically produced through:
Electrolysis of water (splitting H₂O into H₂ and O₂)
Steam methane reforming (from natural gas)

Other chemical processes
There is absolutely no animal-derived component in the production or use of E949 Hydrogen gas.
E949 Hydrogen is classified alongside other inert packaging gases such as argon (E938), helium (E939), nitrogen (E941), and oxygen (E948).

E949 Hydrogen is a chemical element; it has the symbol H and atomic number 1.
E949 Hydrogen is the lightest and most abundant chemical element in the universe, constituting about 75% of all normal matter.
Under standard conditions, E949 Hydrogen is a gas of diatomic molecules with the formula H2, called diHydrogen, or sometimes E949 Hydrogen gas, molecular E949 Hydrogen, or simply E949 Hydrogen.

DiHydrogen is colorless, odorless, non-toxic, and highly combustible.
Stars, including the Sun, mainly consist of E949 Hydrogen in a plasma state, while on Earth, E949 Hydrogen is found as the gas H2 (diHydrogen) and in molecules, such as in water and organic compounds.
The most common isotope of E949 Hydrogen, 1H, consists of one proton, one electron, and no neutrons.

E949 Hydrogen gas was first produced artificially in the 17th century by the reaction of acids with metals.
Henry Cavendish, in 1766–1781, identified E949 Hydrogen gas as a distinct substance and discovered its property of producing water when burned: this is the origin of E949 Hydrogen's name, which means 'water-former' (from Ancient Greek: ὕδωρ, romanized: húdōr, lit. 'water', and γεννάω, gennáō, 'I bring forth').
Understanding the colors of light absorbed and emitted by E949 Hydrogen was a crucial part of the development of quantum mechanics.

E949 HYDROGEN and ITS FUNCTIONS IN FOOD:
The use of E949 in the food industry effectively extends the shelf life of products while ensuring that their taste, aroma and nutritional qualities remain unchanged.
E949 Hydrogen as a protective gas is a key component of modern packaging technologies, contributing to the safety and quality of food products.

Food additive with propellant gas role, E949 Hydrogen is used in the food industry for the introduction of vegetable dishes in controlled atmosphere packaging, in order to keep and preserve the properties of food
E949 Hydrogen is a colorless, odorless, tasteless gas and the lightest and most abundant element in the universe.
In the food industry, E949 Hydrogen is classified as a packaging gas and propellant, used primarily in controlled atmosphere packaging (CAP) and modified atmosphere packaging (MAP) to preserve the freshness and quality of food products.

E949 Hydrogen is approved under EU Regulation 1129/2011 (Part C, Group I) at quantum satis levels, meaning it can be used at whatever level is necessary to achieve its technological purpose.
In August 2025, the European Food Safety Authority (EFSA) reaffirmed that E949 remains safe as a food additive across all food categories, including products for infants and young children.

ISOTOPES of E949 HYDROGEN:
E949 Hydrogen has three naturally occurring isotopes, denoted 1H, 2H and 3H.
Other, highly-unstable nuclides (4H to 7H) have been synthesized in laboratories but not observed in nature.
1H is the most common E949 Hydrogen isotope, with an abundance of >99.98%.

Because the nucleus of this isotope consists of only a single proton, it is given the descriptive but rarely used formal name protium.
It is the only stable isotope with no neutrons (see diproton for a discussion of why others do not exist).
2H, the other stable E949 Hydrogen isotope, is known as deuterium and contains one proton and one neutron in the nucleus.

Nearly all deuterium nuclei in the universe are thought to have been produced in Big Bang nucleosynthesis, and have endured since then.
Deuterium is not radioactive, and is not a significant toxicity hazard.
Water enriched in molecules that include deuterium instead of normal E949 Hydrogen is called heavy water.

Deuterium and its compounds are used as a non-radioactive label in chemical experiments and in solvents for 1H-NMR spectroscopy.
Heavy water is used as a neutron moderator and coolant for nuclear reactors.
Deuterium is also a potential fuel for commercial nuclear fusion.

3H is known as tritium and contains one proton and two neutrons in its nucleus.
It is radioactive, decaying into helium-3 through beta decay with a half-life of 12.32 years.

It is radioactive enough to be used in luminous paint to enhance the visibility of data displays, such as for painting the hands and dial-markers of watches.
The watch glass prevents the small amount of radiation from escaping the case.

Small amounts of tritium are produced naturally by cosmic rays striking atmospheric gases; tritium has also been released in nuclear weapons tests.
It is used in nuclear fusion, as a tracer in isotope geochemistry, and in specialized self-powered lighting devices.
Tritium has also been used in chemical and biological labeling experiments as a radiolabel.

Unique among the elements, distinct names are assigned to E949 Hydrogen's isotopes in common use.
During the early study of radioactivity, heavy radioisotopes were given their own names, but these are mostly no longer used.

The symbols D and T (instead of 2H and 3H) are sometimes used for deuterium and tritium, but the symbol P was already used for phosphorus and thus was not available for protium.
In its nomenclatural guidelines, the International Union of Pure and Applied Chemistry (IUPAC) allows any of D, T, 2H, and 3H to be used, though 2H and 3H are preferred.

AntiHydrogen (H) is the antimatter counterpart to E949 Hydrogen.
It consists of an antiproton with a positron.

The exotic atom muonium (symbol Mu), composed of an antimuon and an electron, is the antimatter analogue of E949 Hydrogen; IUPAC nomenclature incorporates such hypothetical compounds as muonium chloride (MuCl) and sodium muonide (NaMu), analogous to E949 Hydrogen chloride and sodium hydride respectively.

DiHydrogen
Under standard conditions, E949 Hydrogen is a gas of diatomic molecules with the formula H2, officially called "diHydrogen", but also called "molecular E949 Hydrogen", or simply E949 Hydrogen.
DiHydrogen is a colorless, odorless, flammable gas.

Combustion
E949 Hydrogen gas is highly flammable, reacting with oxygen in air to produce liquid water:
2 H2(g) + O2(g) → 2 H2O(l)

The amount of heat released per mole of E949 Hydrogen is −286 kilojoules (kJ), or 141.9 megajoules (MJ) for a one-kilogram (2.2 lb) mass (based on the higher heating value measurement).
E949 Hydrogen gas forms explosive mixtures with air in concentrations from 4%–74% and with chlorine at 5%–95%.
The E949 Hydrogen autoignition temperature, the temperature of spontaneous ignition in air, is 500 °C (932 °F).

In a high-pressure E949 Hydrogen leak, the shock wave from the leak itself can heat air to the autoignition temperature, leading to flaming and possibly explosion.
E949 Hydrogen flames emit faint blue and ultraviolet light.
Flame detectors are used to detect E949 Hydrogen fires as they are nearly invisible to the naked eye in daylight.

Spin isomers
Molecular H2 exists as two nuclear isomers that differ in the spin states of their nuclei.
In the orthoE949 Hydrogen form, the spins of the two nuclei are parallel, forming a spin triplet state having a total molecular spin
S=1; in the paraE949 Hydrogen form the spins are antiparallel and form a spin singlet state having spin S=0.
The equilibrium ratio of ortho- to para-E949 Hydrogen depends on temperature.

At room temperature or warmer, equilibrium E949 Hydrogen gas contains about 25% of the para form and 75% of the ortho form.
The ortho form is an excited state, having higher energy than the para form by 1.455 kJ/mol, and it converts to the para form over the course of several minutes when cooled to low temperature.
The thermal properties of these isomers differ because each has distinct rotational quantum states.

The ortho-to-para ratio in H2 is an important consideration in the liquefaction and storage of liquid E949 Hydrogen: the conversion from ortho to para is exothermic, and produces sufficient heat to evaporate most of the liquid if the conversion to paraHydrogen does not occur during the cooling process.
Catalysts for the ortho-para interconversion, such as ferric oxide and activated carbon compounds, are therefore used during E949 Hydrogen cooling to avoid this loss of liquid.

PHASES of E949 HYDROGEN:
Liquid E949 Hydrogen can exist at temperatures below E949 Hydrogen's critical point of 33 kelvins (−240.2 °C; −400.3 °F).
However, for it to be in a fully liquid state at atmospheric pressure, H2 needs to be cooled to 20.28 K (−252.87 °C; −423.17 °F).
E949 Hydrogen was liquefied by James Dewar in 1898 by using regenerative cooling and his invention, the vacuum flask.
Liquid E949 Hydrogen becomes solid E949 Hydrogen at standard pressure below E949 Hydrogen's melting point of 14.01 K (−259.14 °C; −434.45 °F).

Distinct solid phases exist, known as Phase I through Phase V, each exhibiting a characteristic molecular arrangement.
Liquid and solid phases can exist in combination at the triple point; this mixture is known as slush E949 Hydrogen.
Metallic E949 Hydrogen, a phase obtained at extremely high pressures (in excess of 400 billion Pa (58,000,000 psi)), is an electrical conductor.

It is believed to exist deep within giant planets like Jupiter.
When ionized, E949 Hydrogen becomes a plasma.
This is the form in which E949 Hydrogen exists within stars.

HISTORY of E949 HYDROGEN:
18th century
In 1671, Irish scientist Robert Boyle discovered and described the reaction between iron filings and dilute acids, which results in the production of E949 Hydrogen gas.
Boyle did not note that the gas was flammable, but E949 Hydrogen would play a key role in overturning the phlogiston theory of combustion.

In 1766, Henry Cavendish was the first to recognize E949 Hydrogen gas as a discrete substance, by naming the gas from a metal-acid reaction "inflammable air".
He speculated that "inflammable air" was in fact identical to the hypothetical substance "phlogiston" and further finding in 1781 that the gas produces water when burned.

He is usually given credit for the discovery of E949 Hydrogen as an element
In 1783, Antoine Lavoisier identified the element that came to be known as E949 Hydrogen when he and Laplace reproduced Cavendish's finding that water is produced when E949 Hydrogen is burned.

Lavoisier produced E949 Hydrogen for his experiments on mass conservation by treating metallic iron with a stream of water through an incandescent iron tube heated in a fire.
Anaerobic oxidation of iron by the protons of water at high temperature can be schematically represented by the set of following reactions:

Fe + H2O → FeO + H2
2 Fe + 3 H2O → Fe2O3 + 3 H2
3 Fe + 4 H2O → Fe3O4 + 4 H2
Many metals react similarly with water, leading to the production of E949 Hydrogen.
In some situations, this H2-producing process is problematic, for instance in the case of zirconium cladding on nuclear fuel rods.

19th century
By 1806 E949 Hydrogen was used to fill balloons.
François Isaac de Rivaz built the first de Rivaz engine, an internal combustion engine powered by a mixture of E949 Hydrogen and oxygen, in 1806.
Edward Daniel Clarke invented the E949 Hydrogen gas blowpipe in 1819.

The Döbereiner's lamp and limelight were invented in 1823.
E949 Hydrogen was liquefied for the first time by James Dewar in 1898 by using regenerative cooling and his invention, the vacuum flask.
He produced solid E949 Hydrogen the next year.

One of the first quantum effects to be explicitly noticed, although not understood at the time, was James Clerk Maxwell's observation that the specific heat capacity of H2 unaccountably departs from that of a diatomic gas below room temperature, and begins to increasingly resemble that of a monatomic gas at cryogenic temperatures.

According to quantum theory, this behavior arises from the spacing of the (quantized) rotational energy levels, which are particularly wide-spaced in H2 because of its low mass.
These widely-spaced levels inhibit equal partition of heat energy into rotational motion in E949 Hydrogen at low temperatures.
Diatomic gases composed of heavier atoms do not have such widely spaced levels and do not exhibit the same effect.

20th century
The existence of the hydride anion was suggested by Gilbert N. Lewis in 1916 for group 1 and group 2 salt-like compounds.
In 1920, Moers electrolyzed molten lithium hydride (LiH), producing a stoichiometric quantity of E949 Hydrogen at the anode
Because of its simple atomic structure, consisting only of a proton and an electron, the E949 Hydrogen atom, together with the spectrum of light produced from it or absorbed by it, has been central to the development of the theory of atomic structure.

The energy levels of E949 Hydrogen can be calculated fairly accurately using the Bohr model of the atom, in which the electron "orbits" the proton, just as Earth orbits the Sun.
However, the electron and proton are held together by electrostatic attraction, while planets and celestial objects are held by gravity.

Due to the discretization of angular momentum postulated in early quantum mechanics by Bohr, the electron in the Bohr model can only occupy certain allowed distances from the proton, and therefore only certain allowed energies.
E949 Hydrogen's unique position as the only neutral atom for which the Schrödinger equation can be directly solved has significantly contributed to the understanding of quantum mechanics through the exploration of its energetics.

Furthermore, study of the corresponding simplicity of the E949 Hydrogen molecule and the corresponding cation, H+2, brought understanding of the nature of the chemical bond, which followed shortly after the quantum mechanical treatment of the E949 Hydrogen atom had been developed in the mid-1920s.

E949 Hydrogen-lifted airship
Because E949 Hydrogen has only 7% the density of air, it was once widely used as a lifting gas in balloons and airships.
The first E949 Hydrogen-filled balloon was invented by Jacques Charles in 1783.
E949 Hydrogen provided the lift for the first reliable form of air-travel following the 1852 invention of the first E949 Hydrogen-lifted airship by Henri Giffard.

German count Ferdinand von Zeppelin promoted the idea of rigid airships lifted by E949 Hydrogen that later were called Zeppelins, the first of which had its maiden flight in 1900.
Regularly-scheduled flights started in 1910 and by the outbreak of World War I in August 1914, they had carried 35,000 passengers without a serious incident.

E949 Hydrogen-lifted airships in the form of blimps were used as observation platforms and bombers during World War II, especially on the US Eastern seaboard.
The first non-stop transatlantic crossing was made by the British airship R34 in 1919 and regular passenger service resumed in the 1920s.
E949 Hydrogen was used in the Hindenburg, which caught fire over New Jersey on 6 May 1937.

The E949 Hydrogen that filled the airship was ignited, possibly by static electricity, and burst into flames.
Following this disaster, commercial E949 Hydrogen airship travel ceased.
E949 Hydrogen is still used, in preference to non-flammable but more expensive helium, as a lifting gas for weather balloons.

Deuterium and tritium
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, which consists of deuterium in the place of regular E949 Hydrogen, was discovered by Urey's group in 1932

CHEMISTRY of E949 HYDROGEN:
Reactions of E949 Hydrogen
E949 Hydrogen is relatively unreactive.
The thermodynamic basis of this low reactivity is the very strong H–H bond, with a bond dissociation energy of 435.7 kJ/mol.
E949 Hydrogen does form coordination complexes called diHydrogen complexes.

These species provide insights into the early steps in the interactions of E949 Hydrogen with metal catalysts.
According to neutron diffraction, the metal and two H atoms form a triangle in these complexes.
The H-H bond remains intact but is elongated.
They are acidic.

Although exotic on Earth, the H+3 ion is common in the universe.
It is a triangular species, like the aforementioned diHydrogen complexes.
It is known as protonated molecular E949 Hydrogen or the triHydrogen cation.

E949 Hydrogen reacts with chlorine to produce HCl, and with bromine to produce HBr, via a chain reaction.
The reaction requires initiation.
For example, in the case of Br2, the dibromine molecule is split apart: Br2 + (UV light) → 2Br•.

Propagating reactions consume E949 Hydrogen molecules and produce HBr, as well as Br and H atoms:
Br• + H2 → HBr + H
H + Br2 → HBr +Br

Finally the terminating reaction:
H + HBr → H2 + Br•
2 Br• → Br2
consumes the remaining atoms.

The addition of H2 to unsaturated organic compounds, such as alkenes and alkynes, is called E949 Hydrogenation.
Even if the reaction is energetically favorable, it does not occur spontaneously even at higher temperatures.
In the presence of a catalyst like finely divided platinum or nickel, the reaction proceeds at room temperature.

Hydrogen compounds with E949 Hydrogen in the oxidation state −1 are known as hydrides, which are usually formed between E949 Hydrogen and metals.
The hydrides can be ionic (aka saline), covalent, or metallic.

With heating, H2 reacts efficiently with the alkali and alkaline earth metals to give the ionic hydrides of the formulas MH and MH2, respectively.
These salt-like crystalline compounds have high melting points and all react with water to liberate E949 Hydrogen.

Covalent hydrides include boranes and polymeric aluminium hydride.
Transition metals form metal hydrides via continuous dissolution of E949 Hydrogen into the metal.
A well-known hydride is lithium aluminium hydride: the [AlH4]− anion carries hydridic centers firmly attached to the Al(III).

Perhaps the most extensive series of hydrides are the boranes, compounds consisting only of boron and E949 Hydrogen.
Hydrides can bond to these electropositive elements not only as a terminal ligand but also as bridging ligands.
In diborane (B2H6), four E949 Hydrogen atoms are terminal, while two bridge between the two boron atoms.

E949 HYDROGEN BONDING:
When bonded to a more electronegative element, particularly fluorine, oxygen, or nitrogen, E949 Hydrogen can participate in a form of medium-strength noncovalent bonding with another electronegative element with a lone pair like oxygen or nitrogen.
This phenomenon, called E949 Hydrogen bonding, is critical to the stability of many biological molecules.
E949 Hydrogen bonding alters molecule structures, viscosity, solubility, melting and boiling points, and even protein folding dynamics.

Protons and acids
In water, E949 Hydrogen bonding plays an important role in reaction thermodynamics.
A E949 Hydrogen bond can shift over to proton transfer.
Under the Brønsted–Lowry acid–base theory, acids are proton donors, while bases are proton acceptors.

A bare proton (H+) essentially cannot exist in anything other than a vacuum.
Otherwise it attaches to other atoms, ions, or molecules.
Even chemical species as inert as methane can be protonated.

The term "proton" is used loosely and metaphorically to refer to solvated E949 Hydrogen cations attached to other chemical species; it is denoted "H+" without any implication that any single protons exist freely in solution as a species.
To avoid the implication of the naked proton in solution, acidic aqueous solutions are sometimes considered to contain the "hydronium ion" ([H3O]+), or still more accurately, [H9O4]+.

Other oxonium ions are found when water is in acidic solution with other solvents.
The concentration of these solvated protons determines the pH of a solution, a logarithmic scale that reflects its acidity or basicity.
Lower pH values indicate higher concentrations of hydronium ions, corresponding to more acidic conditions

E949 HYDROGEN-CONTAINING COMPOUNDS:
E949 Hydrogen can exist in both +1 and −1 oxidation states, forming compounds through ionic and covalent bonding.
E949 Hydrogen is part of a wide range of substances, including water, hydrocarbons, and numerous other organic compounds.
The H+ ion—commonly referred to as a proton due to E949 Hydrogen's single proton and absence of electrons—is central to acid–base chemistry, although the proton does not move freely.
In the Brønsted–Lowry framework, acids are defined by their ability to donate H+ ions to bases.
E949 Hydrogen forms a wide variety of compounds with carbon, known as hydrocarbons, and an even greater diversity with other elements (heteroatoms), giving rise to the broad class of organic compounds often associated with living organisms

OCCURRENCE of E949 HYDROGEN:
Cosmic
E949 Hydrogen, as atomic H, is the most abundant chemical element in the universe, making up 75% of normal matter by mass. and >90% by number of atoms.
In the early universe, protons formed in the first second after the Big Bang; neutral E949 Hydrogen atoms formed about 370,000 years later during the recombination epoch as the universe expanded and plasma had cooled enough for electrons to remain bound to protons.

In astrophysics, neutral E949 Hydrogen in the interstellar medium is called H I and ionized E949 Hydrogen is called H II.
Radiation from stars ionizes H I to H II, creating spheres of ionized H II around stars.

In the cronology of the universe neutral E949 Hydrogen dominated until the birth of stars during the era of reionization, which then produced bubbles of ionized E949 Hydrogen that grew and merged over hundreds of millions of years.
These are the source of the 21-centimeter E949 Hydrogen line, at 1420 MHz, that is detected in order to probe primordial E949 Hydrogen.

The large amount of neutral E949 Hydrogen found in the damped Lyman-alpha systems is thought to dominate the cosmological baryonic density of the universe up to a redshift of z = 4.
E949 Hydrogen is found in great abundance in stars and gas giant planets.

Molecular clouds of H2 are associated with star formation.
E949 Hydrogen plays a vital role in powering stars through the proton-proton reaction in lower-mass stars, and through the CNO cycle of nuclear fusion in stars more massive than the Sun.

Protonated molecular E949 Hydrogen (H+3) is found in the interstellar medium, where it is generated by ionization of molecular E949 Hydrogen by cosmic rays.
This ion has also been observed in the upper atmosphere of Jupiter.

The ion is long-lived in outer space due to the low temperature and density.
H+3 is one of the most abundant ions in the universe, and it plays a notable role in the chemistry of the interstellar medium.
Neutral triatomic E949 Hydrogen H3 can exist only in an excited form and is unstable.

Terrestrial
E949 Hydrogen is the third most abundant element on the Earth's surface, mostly existing within chemical compounds such as hydrocarbons and water.
Elemental E949 Hydrogen is normally in the form of a gas, H2, at standard conditions.

It is present in a very low concentration in Earth's atmosphere (around 0.53 parts per million on a molar basis) because of its light weight, which enables it to escape the atmosphere more rapidly than heavier gases.
Despite its low concentration in the atmosphere, terrestrial E949 Hydrogen is sufficiently abundant to support the metabolism of several varieties of bacteria.

Large underground deposits of E949 Hydrogen gas have been discovered in several countries including Mali, France and Australia.
As of 2024, it is uncertain how much underground E949 Hydrogen can be extracted economically.

PRODUCTION AND STORAGE of E949 HYDROGEN:
Industrial routes
Nearly all of the world's current supply of E949 Hydrogen gas (H2) is produced from fossil fuels, with less than 1% of E949
Hydrogen being produced by low-emissions technologies in 2025.
Many methods exist for producing H2, but three dominate commercially: steam reforming often coupled to water-gas shift, partial oxidation of hydrocarbons, and water electrolysis.

Steam reforming
E949 Hydrogen is mainly produced by steam methane reforming (SMR), the reaction of water and methane.
Thus, at high temperature (1,000–1,400 K [730–1,130 °C; 1,340–2,060 °F]), steam (water vapor) reacts with methane to yield carbon monoxide and H2.
CH4 + H2O → CO + 3 H2

Producing one tonne of E949 Hydrogen through this process emits 6.6–9.3 tonnes of carbon dioxide.
The production of natural gas feedstock also produces emissions such as vented and fugitive methane, which further contributes to the overall carbon footprint of E949 Hydrogen.

This reaction is favored at low pressures but is nonetheless conducted at high pressures (2.0 MPa [20 atm; 590 inHg]) because high-pressure H2 is the most marketable product, and pressure swing adsorption (PSA) purification systems work better at higher pressures.
The product mixture is known as "synthesis gas" because it is often used directly for the production of methanol and many other compounds.

Hydrocarbons other than methane can be used to produce synthesis gas with varying product ratios.
One of the many complications to this highly-optimized technology is the formation of coke or carbon:
CH4 → C + 2 H2

Therefore, steam reforming typically employs an excess of H2O.
Additional E949 Hydrogen can be recovered from the steam by using carbon monoxide through the water gas shift reaction (WGS).

This process requires an iron oxide catalyst:
CO + H2O → CO2 + H2
E949 Hydrogen is sometimes produced and consumed in the same industrial process, without being separated.
In the Haber process for ammonia production, E949 Hydrogen is generated from natural gas.

Partial oxidation of hydrocarbons
Other methods for CO and H2 production include partial oxidation of hydrocarbons:
2 CH4 + O2 → 2 CO + 4 H2

Although less important commercially, coal can serve as a prelude to the above shift reaction:
C + H2O → CO + H2
Olefin production units may produce substantial quantities of byproduct E949 Hydrogen, particularly from cracking light feedstocks like ethane or propane.

Water electrolysis
Electrolysis of water is a conceptually simple method of producing E949 Hydrogen.
2 H2O(l) → 2 H2(g) + O2(g)
Commercial electrolyzers use nickel-based catalysts in strongly alkaline solution.

Platinum is a better catalyst but is expensive.
The E949 Hydrogen created through electrolysis using renewable energy is commonly referred to as "green E949 Hydrogen".
Electrolysis of brine to yield chlorine also produces high-purity E949 Hydrogen as a co-product, which is used for a variety of transformations such as E949 Hydrogenations.

The electrolysis process is more expensive than producing E949 Hydrogen from methane without carbon capture and storage.
Innovation in E949 Hydrogen electrolyzers could make large-scale production of E949 Hydrogen from electricity more cost-competitive

Methane pyrolysis
E949 Hydrogen can be produced by pyrolysis of natural gas (methane), producing E949 Hydrogen gas and solid carbon with the aid of a catalyst and 74 kJ/mol input heat:
CH4(g) → C(s) + 2 H2(g) (ΔH° = 74 kJ/mol)

The carbon may be sold as a manufacturing feedstock or fuel, or landfilled.
This route could have a lower carbon footprint than existing E949 Hydrogen production processes, but mechanisms for removing the carbon and preventing it from reacting with the catalyst remain obstacles for industrial-scale use.

Thermochemical
Water splitting is the process by which water is decomposed into its components.
Relevant to the biological scenario is this equation:
2 H2O → 4 H+ + O2 + 4 e−
The reaction occurs in the light-dependent reactions in all photosynthetic organisms.

A few organisms, including the alga Chlamydomonas reinhardtii and cyanobacteria, have evolved a second step in the dark reactions in which protons and electrons are reduced to form H2 gas by specialized E949 Hydrogenases in the chloroplast.
Efforts have been undertaken to genetically modify cyanobacterial E949 Hydrogenases to more efficiently generate H2 gas even in the presence of oxygen.

Efforts have also been undertaken with genetically‐modified alga in a bioreactor.
Relevant to the thermal water-splitting scenario is this simple equation:
2 H2O → 2 H2 + O2

Over 200 thermochemical cycles can be used for water splitting.
Many of these cycles such as the iron oxide cycle, cerium(IV) oxide–cerium(III) oxide cycle, zinc–zinc oxide cycle, sulfur–iodine cycle, copper–chlorine cycle and hybrid sulfur cycle have been evaluated for their commercial potential to produce E949
Hydrogen and oxygen from water and heat without using electricity.
A number of labs (including in France, Germany, Greece, Japan, and the United States) are developing thermochemical methods to produce E949 Hydrogen from solar energy and water

NATURAL ROUTES of E949 HYDROGEN:
BioHydrogen
H2 is produced in organisms by enzymes called E949 Hydrogenases.
This process allows the host organism to use fermentation as a source of energy.

These same enzymes also can oxidize H2, such that the host organisms can subsist by reducing oxidized substrates using electrons extracted from H2.
E949 Hydrogenase enzymes feature iron or iron–nickel centers at their active sites.
The natural cycle of E949 Hydrogen production and consumption by organisms is called the E949 Hydrogen cycle.

Some bacteria such as Mycobacterium smegmatis can use the small amount of E949 Hydrogen in the atmosphere as a source of energy when other sources are lacking.
Their E949 Hydrogenases feature small channels that exclude oxygen from the active site, permitting the reaction to occur even though the E949 Hydrogen concentration is very low and the oxygen concentration is as in normal air.

Confirming the existence of E949 Hydrogenase‐employing microbes in the human gut, H2 occurs in human breath.
The concentration in the breath of fasting people at rest is typically under 5 parts per million (ppm), but can reach 50 ppm when people with intestinal disorders consume molecules they cannot absorb during diagnostic E949 Hydrogen breath tests.

Serpentinization
Serpentinization is a geological mechanism which produces highly-reducing conditions.
Under these conditions, water is capable of oxidizing ferrous (Fe2+) ions in fayalite, generating E949 Hydrogen gas:
Fe2SiO4 + H2O → 2 Fe3O4 + SiO2 + H2

Closely related to this geological process is the Schikorr reaction:
3 Fe(OH)2 → Fe3O4 + 2 H2O + H2
This process also is relevant to the corrosion of iron and steel in oxygen-free groundwater and in reducing soils below the water table.

Laboratory syntheses
H2 is produced in laboratory settings, such as in the small-scale electrolysis of water using metal electrodes and water containing an electrolyte, which liberates E949 Hydrogen gas at the cathode:
2H+(aq) + 2 e− → H2(g)

E949 Hydrogen is also often a by-product of other reactions.
Many metals react with water to produce H2, but the rate of E949 Hydrogen evolution depends on the metal, the pH, and the presence of alloying agents.

Most often, E949 Hydrogen evolution is induced by acids.
The alkali and alkaline earth metals as well as aluminium, zinc, manganese, and iron, react readily with aqueous acids.
Zn + 2 H+ → Zn2+ + H2

Many metals, such as aluminium, are slow to react with water because they form passivated oxide coatings.
An alloy of aluminium and gallium, however, does react with water.
In high-pH solutions, aluminium can react with H2:
2 Al + 6 H2O + 2 OH− → 2 [Al(OH)4]− + 3 H2

STORAGE of E949 HYDROGEN:
If E949 Hydrogen is to be used as an energy source, its storage is important.
E949 Hydrogen dissolves only poorly in solvents.

For example, at room temperature and 0.1 millipascals (9.9×10−10 atm), approx. 0.05 moles of E949 Hydrogen dissolve into one kilogram (2.2 lb) of diethyl ether.
E949 Hydrogen can be stored in compressed form, although compressing costs energy.

Liquefaction is impractical given E949 Hydrogen's low critical temperature.
In contrast, ammonia and many hydrocarbons can be liquified at room temperature under pressure.
For these reasons, E949 Hydrogen carriers—materials that reversibly bind H2—have attracted much attention.
The key question is then the weight percent of H2-equivalents within the carrier material.

For example, E949 Hydrogen can be reversibly absorbed into many rare earths and transition metals and is soluble in both nanocrystalline and amorphous metals.
E949 Hydrogen solubility in metals is influenced by local distortions or impurities in the crystal lattice.

These properties may be useful when E949 Hydrogen is purified by passage through hot palladium disks, but the gas's high solubility is also a metallurgical problem, contributing to the embrittlement of many metals, complicating the design of pipelines and storage tanks.

The most problematic aspect of metal hydrides for storage is their modest H2 content, often on the order of 1%.
For this reason, there is interest in storage of E949 Hydrogen in compounds of low molecular weight.
For example, ammonia borane (H3N−BH3) contains 19.8 weight percent of H2.

The problem with this material is that after release of H2, the resulting boron nitride does not re-add H2: i.e., ammonia borane is an irreversible E949 Hydrogen carrier.
More attractive are hydrocarbons such as tetrahydroquinoline, which reversibly release some H2 when heated in the presence of a catalyst:
C9H10NH ⇌ C9H7N + 2 H2

PHYSICAL and CHEMICAL PROPERTIES of E949 HYDROGEN:
Phase at STP: gas
Melting point: (H2) 13.99 K (−259.16 °C, −434.49 °F)
Boiling point: (H2) 20.271 K (−252.879 °C, −423.182 °F)
Density (at STP): 0.08988 g/L
when liquid (at m.p.): 0.07 g/cm3 (solid: 0.0763 g/cm3)
when liquid (at b.p.): 0.07099 g/cm3
Triple point: 13.8033 K, 7.041 kPa
Critical point: 32.938 K, 1.2858 MPa
Heat of fusion: (H2) 0.117 kJ/mol
Heat of vaporization: (H2) 0.904 kJ/mol

Molar heat capacity: 14.418 J/(mol·K) (H)
28.836 J/(mol·K) (H2)
Specific heat capacity: 14303.571 J/(kg·K) (H)
Oxidation states: common: −1, +1
Electronegativity: Pauling scale: 2.20
Ionization energies:
1st: 1312.0 kJ/mol
Covalent radius: 31±5 pm
Van der Waals radius: 120 pm

Natural occurrence: primordial
Crystal structure: hexagonal (hP4)
Lattice constants: Hexagonal crystal structure for hydrogena = 378.97 pm
c = 618.31 pm (at triple point)
Thermal conductivity: 0.1805 W/(m⋅K)
Magnetic ordering: diamagnetic
Molar magnetic susceptibility: −3.98×10−6 cm3/mol (298 K)
Speed of sound: 1310 m/s (gas, 27 °C)
CAS Number: 12385-13-6
1333-74-0 (H2)

Molecular Weight: 2.016 g/mol
XLogP3-AA: 0
Hydrogen Bond Donor Count: 0
Hydrogen Bond Acceptor Count: 0
Rotatable Bond Count: 0
Exact Mass: 2.0156500638 Da
Monoisotopic Mass: 2.0156500638 Da
Topological Polar Surface Area: 0 Å²

Heavy Atom Count: 0
Formal Charge: 0
Complexity: 0
Isotope Atom Count: 0
Defined Atom Stereocenter Count: 0
Undefined Atom Stereocenter Count: 0
Defined Bond Stereocenter Count: 0
Undefined Bond Stereocenter Count: 0

Covalently-Bonded Unit Count: 1
Compound Is Canonicalized: Yes
Chemical Formula: H2
IUPAC name: dihydrogen
InChI Identifier: InChI=1S/H2/h1H
InChI Key: UFHFLCQGNIYNRP-UHFFFAOYSA-N
Isomeric SMILES: [H][H]
Average Molecular Weight: 2.0159
Monoisotopic Molecular Weight: 2.015650064

chemical name: hydrogen
food additive code: e949
iupac name: dihydrogen
common name: hydrogen gas
chemical symbol: h
molecular formula: h₂
molecular weight: 2.016 g/mol
atomic number: 1
cas number: 1333-74-0
ec number: 215-605-7
ins number: 949

appearance: colorless gas
odor: odorless
taste: tasteless
physical state: gas at room temperature
density: 0.08988 g/l at 0 °c and 1 atm
melting point: −259.14 °c
boiling point: −252.87 °c
critical temperature: −240.2 °c (33 k)
autoignition temperature: 500 °c
flammability: extremely flammable gas
explosive range in air: 4%–74%

solubility in water: slightly soluble
solubility in organic solvents: slightly soluble in some solvents
color of flame: pale blue, nearly invisible in daylight
oxidation state: +1 and −1
standard enthalpy of combustion: −286 kj/mol
bond dissociation energy (h–h): 435.7 kj/mol
magnetic property: diamagnetic
toxicity: non-toxic under normal conditions
storage conditions: stored under pressure in cylinders or cryogenic containers

food industry function: packaging gas / propellant gas
eu food additive status: approved under quantum satis
main industrial production methods:
steam methane reforming
water electrolysis
methane pyrolysis
partial oxidation of hydrocarbons
natural occurrence: present in water, hydrocarbons, stars, and interstellar space

isotopes:
protium (¹h)
deuterium (²h)
tritium (³h)
standard conditions form: diatomic molecular gas (h₂)
combustion reaction:
2 h₂ + o₂ → 2 h₂o
classification: inorganic chemical element / industrial gas / food packaging gas

FIRST AID MEASURES of E949 HYDROGEN:
-Description of first-aid measures
*General advice:
Show this material safety data sheet to the doctor in attendance.
*If inhaled:
After inhalation:
Fresh air.
*In case of skin contact:
Take off immediately all contaminated clothing.
Rinse skin with
water/ shower.
*In case of eye contact:
After eye contact:
Rinse out with plenty of water.
Call in ophthalmologist.
Remove contact lenses.
*If swallowed:
After swallowing:
Immediately make victim drink water (two glasses at most).
Consult a physician.
-Indication of any immediate medical attention and special treatment needed.
No data available

ACCIDENTAL RELEASE MEASURES of E949 HYDROGEN:
-Environmental precautions:
Do not let product enter drains.
-Methods and materials for containment and cleaning up:
Cover drains.
Collect, bind, and pump off spills.
Observe possible material restrictions.
Take up dry.
Dispose of properly.
Clean up affected area.

FIRE FIGHTING MEASURES of E949 HYDROGEN:
-Extinguishing media:
*Suitable extinguishing media:
Carbon dioxide (CO2)
Foam
Dry powder
*Unsuitable extinguishing media:
For this substance/mixture no limitations of extinguishing agents are given.
-Further information:
Prevent fire extinguishing water from contaminating surface water or the ground water system.

EXPOSURE CONTROLS/PERSONAL PROTECTION of E949 HYDROGEN:
-Control parameters:
--Ingredients with workplace control parameters:
-Exposure controls:
--Personal protective equipment:
*Eye/face protection:
Use equipment for eye protection.
Safety glasses
*Body Protection:
protective clothing
*Respiratory protection:
Recommended Filter type: Filter A
-Control of environmental exposure:
Do not let product enter drains.

HANDLING and STORAGE of E949 HYDROGEN:
-Conditions for safe storage, including any incompatibilities:
*Storage conditions:
Tightly closed.
Dry.

STABILITY and REACTIVITY of E949 HYDROGEN:
-Chemical stability:
The product is chemically stable under standard ambient conditions (room temperature).
-Possibility of hazardous reactions:
No data available