Hydrogen Facts and Figures

I went out on a quest to gather bits and pieces of information I felt was relevant to Hydrogen Gas as produced during electrolysis of water. This is by no means a complete list, it is rather a collection of pertinent facts I felt were relevant to the electrolysis of water and the subsequent handling of the gas. As such this list will likely change as I gain knowledge on the subject.

Hydrogen Facts and Figures

Represented in the Periodic Table by the symbol H.

Has atomic weight of 1.

Has one proton and one electron.

Sometimes has one or two neutrons.

Atomic mass of 1.00974 amu

Is the lightest of elements, and the most common, comprising 75% of the mass of the known universe and 90% of all atoms.

Almost never found in its free state on Earth.

Largest industrial uses are fossil fuel upgrading also known as hydro-cracking among others and ammonia production for fertilizer.

Hydrogen is classified as a flammable gas and will react with any of a host of oxidizers. Notably, Air, Chlorine, Florine, Nitric Oxide, Nitrogen Dioxide, and Oxygen.

Hydrogen can violently and spontaneously react with Chlorine and Florine at room temperature.

Hydrogen will burn at approximately 4% concentration in air and the upper limit is approximately 75% concentration in air. EngineeringToolbox.com has a comparison of the different flammable gases.

Hydrogen will ignite at 560 degrees Celsius or 1040 degrees Fahrenheit. The hydrogen ignition temperature behaves on a curve where the ignition temperature actually is lower at lower concentrations and will ignite as low as 910F at 8-15% volume in air. At concentrations similar to those found in electrolysis, the heat ignition point is about 1080F.
See Hydrogen Leakage Detection & Safety, Jones, Pg 16

Hydrogen burns with oxygen in the ultraviolet range making the flame nearly invisible to the naked eye.

Hydrogen has two different types of diatomic molecules that are identified by the spin of their nuclei. The excited state orthohydrogen forms about 25 percent of hydrogen gas at standard temperature and pressure while parahydrogen makes up the rest.

Hydrogen has an adiabatic flame temperature in air of 3712.73 degrees Fahrenheit.

Hydrogen has a flame quenching distance of approximately .3mm and a mesh engineered to less than this distance will prevent flame propagation. This distance is equal to .01181 In or about 3/256th of an inch(.01172In). This is in the same range as the diameter of a human hair. Reference

According to testing done by Dr William Rhodes, the flame propagation rate of ducted Hydrogen-Oxygen gas is 8160 feet per second or approximately Mach 7.5.

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