Hydrogen (H2) the lightest element, has a gaseous specific gravity of 0.0695 and a boiling point of -423 F (-252.8 C) at atmospheric pressure. It is a colorless, odorless, tasteless, flammable gas found at concentrations of about 0.0001 % in air. Hydrogen is produced by several methods, including steam/methane reforming, dissociation of ammonia, and recovery from by-product streams from chemical manufacturing and petroleum reforming. Hydrogen can be stored and transported as either a gas a cryogenic liquid.
In the welding industry, hydrogen is used as a fuel in underwater oxy-hydrogen torches, and for metal welding and brazing. Hydrogen is widely used in petroleum refining processes such as hydrotreating, catalytic reforming, and hydro-cracking. It is used in the food industry for turning inedible grease into soaps and animal feeds. It is a raw material for innumerable chemical processes ranging from the manufacturing of high-density polyethylene and polypropylene resins to the hydrogenation of food-grade oils. Hydrogen is also used as a reducing gas in metals processing operations. Applications in the electronics industry are found in the manufacture of silicon wafers and computer chips. Rocket engine fuel is another major use for hydrogen since weight and energy considerations are paramount to its success.
DOT Name: Hydrogen
DOT Hazard Class: Flammable Gas
DOT Label: Flammable Gas
DOT ID No.: UN1049
CAS No.: 1333-74-0
Valve Outlet: CGA 350, LB-CGA 110/170
Physical State in High Pressure Cylinder: Gas
Fire Potential: Flammable
Physical Properties of Oxygen
Molecular Weight: 2.016 lb/mol
Specific Volume at 70°F and 1 atm: 192.0 ft3/lb (11.99 m3/kg)
Specific Heat: 6.87 BTU/lbmol-deg F@ 70 deg. F
Specific Gravity: 0.069
Gas Density: 0.005210 lb/ ft3 @ 70 deg. F. 14.7 PSIA
Boiling Point: Temperature: -423.0 deg. F (-252.8 deg. C)
Liquid Density: 4.43 lb./ft3
Latent Heat: 95.0 BTU/lb.
Critical Point : Temperature: -400.3 deg. F
Pressure: 187.51 PSIA
Melting Point: Temperature: -434.8 deg. F
Pressure: 1.021 PSIA
Discovered in 1766, the hydrogen atom is the simplest atom that can possibly exist. The most common isotope is composed of a single proton and an electron. There is relatively little hydrogen gas in the earth’s atmosphere, but there are plenty of hydrogen atoms in compounds like water. Consider that every molecule of water in all the seas, lakes and streams contains two hydrogen atoms; hydrogen is one of the ten most abundant elements on the earth.
Hydrogen is a light colorless gas, which has no smell or taste when pure. It burns explosively in air or oxygen to form water, H2O. It combines directly with nonmetals to form compounds. With reactive metals such as lithium, sodium, and calcium, hydrogen forms metal hydrides. These decompose in water and liberate hydrogen gas. The cation H+, is characteristic of acids in aqueous solution.
The principal industrial sources of hydrogen are:
- Electrolysis of aqueous solutions of sodium chloride, table salt.
- reaction of carbon with water to form carbon monoxide and hydrogen gas,
- cracking processes in oil refineries, and
- Reaction of methane, CH4 (in natural gas), or other simple hydrocarbons with steam.
There are three isotopes of hydrogen:
1. 1H, occurs in nature at 99.9985% abundance,
2. 2H, or D, also known as deuterium or heavy hydrogen occurs in nature at 0.015% abundance, and
3. 3H, or T, also known as tritium, are found only in trace amounts.
The most common compound is deuterium oxide, D2O, or heavy water. This name is appropriate because the deuterium atom is twice as heavy as 1H. Since deuterium occurs naturally, in every 7000 molecules of ordinary H2O, there is one D2O. Heavy water can be prepared by prolonged electrolysis of ordinary water. Approximately 100,000 gallons of water have to be carefully electrolyzed to produce a single gallon of pure heavy water. Considering the cost of the electrical energy involved in such a process, heavy water is generally regarded as a scarce commodity. Heavy water is a suitable and convenient moderator in nuclear reactors.
Tritium, 3H, is extremely rare in nature. It occurs in ordinary water, but only in portions of one atom for every 1018atoms of 1H. Tritium is more effectively produced by nuclear reactions than by separations from water by electrolysis.