CHARACTERISTIC OF HYDROGEN

Hydrogen is colourless, tasteless, and odourless gas. Due to its high reactivity and boiling point the use of odorants is limited. Hydrogen flame is almost invisible in daylight. It diffuses quickly even through seemingly high-density materials (some metals and plastic). It is lighter than air and, in the atmosphere, rises at the speed of 20 m per second. If expanding rapidly it can self-ignite.

It has very low ignition energy and can be initiated with energy of only 0.02 J. The critical temperature of hydrogen is -239.96 °C. It cannot occur in a liquid state above this temperature. That is why storing hydrogen in a liquid state is energetically and economically demanding. Hydrogen also causes so-called hydrogen embrittlement and hydrogen corrosion. These processes occur mainly where the materiel is under mechanical stress and their initial phases is not visible to an eye as they happen inside the material. In case of temperature rises faster than 20 K per hour, hydrogen is trapped in the cracks, accumulates in the cavities (so called "hydrogen traps") and causes the expansion of the cracks. [1]

Isotopes of Hydrogen

A hydrogen atom consists of one proton. It is the simplest isotope in the universe. The isotopes are differentiated by the number of neutrons they contain. Hydrogen has three known isotopes that occur naturally on Earth. The most abundant isotope is protium (₁H), consisting of one proton and no neutron. The next isotope is deuterium (₂H), consisting of one proton and one neutron. In chemical formulas, it can be found under the symbol D. The third isotope is tritium (₃H), consisting of one proton and two neutrons. Deuterium Oxide D₂O (Heavy Water) is present in water. Its concentration grows during water electrolysis. Its melting point (3.79 °C) and boiling point (101.4 °C) are higher than for H₂O. Tritium is a radioactive gas with weak β radiation, and unlike deuterium, it is unstable and has a half-life of 12,3 years. In chemical formulas, it can be found under the symbol T. It is produced in nuclear reactors during the production of plutonium from natural uranium. It is used in hydrogen bombs, fluorescent colours, or luminous clock hands.[2]