The simplest of the elements, containing a single proton and electron each, of mass almost unity, is the first member of the periodic table. Data may vary from different sources; solid at 4.2 K (d 0.089), H has the atomic number (AN) 1, atomic weight (AW) 1.008 g, melting point (mp) —259.14°C, and boiling point (bp) —252.87°C (d 0.071 at 20.4 K). He has a AN 2, AW 4.0026 g, mp —272.2°C (20 atm), and bp —268.93°C (specific gravity 0.124).

Commercial consumption at present is mostly in synthetic fuels, say from coal, mineral oils, petroleum reformation (refineries), and iron and copper ore reductions. Hydrogen is very important because of the ver­satility of its physical, chemical, and biological properties. More impor­tantly for our purposes, is its potential as a source of energy. Hydrogen liquefies at 33.2 K, 12.8 atm, and 0.03 g/mL and occupies a negligible volume (22.4 times less), compared to its gaseous state. Solid hydrogen and helium are academic ideas. When hydrogen combines with oxygen in a volume ratio of 2:1, heat is generated and the product is water in a vapor state. The reaction in a vapor state occurs with a reduction of volume to 1/3 and water vapor to water 1/22, which means the reaction is favored at a higher pressure; alternatively, the change in volume is compensated by utilizing some of the heat that evolves. The calculations are already there. Hydrogen as a combustion fuel or as a material for a fuel cell is less attractive than the fusion reaction such as that which occurs in the sun. Taking it as a model, we may be able to harness huge amounts of thermal and traditional energies, but we should also learn how to manage and handle such enormous outbursts of energy. Two protons fuse to yield a deuterium, a positron, and a neutrino; the last one is the clue to the release of energy that is not yet fully understood by science;

2H1 ^ e+ + v + H2 H2 + H1 ^ H3 + v 2H3 ^ He4 + 2H1

Solar constant = 1.968 cal/(cm2 • min) = 3.86 X 1033 erg/s = 1.373 kW/m2; even at such a long distance, we are unable to use all the energies.

Hydrogen in absence of air or oxygen, or in vacuum, will not burn, but may have a kind of combustion to produce ammonia in air or nitrogen. Combustion of hydrogen in our atmosphere does not produce simple water vapor, but mixture of others, i. e., ammonia and NOxS (nitrogen and oxygen combine at the vicinity of high temperature generated).

Cryogenic and space research have taught us many more lessons. Liquid hydrogen can be stored in special containers (cylinders), or trans­ported through pipes, and is almost an ideal fuel for rockets and space­ships, perhaps next to azides. But at higher altitudes or in space, in the absence of atmosphere, optimal liquid oxygen is also needed to perform the dynamism or thrust. Water vapor is transformed into ice particles instantly due to the very low temperature in space. Liquid hydrogen for such research or experiment is generated at a very high cost, i. e., elec­trolytic splitting of water. The alternate resource of hydrogen is a by­product in the caustic soda plant. A similar minor and indirect source of hydrogen is water gas (C + H2O ^ CO + H2), almost obsolete for any large-scale production. None of these examples are renewable in nature, continue to be energy and labor intensive, and cannot stand as com­petitors as fuel or energy resources. Other commercial sources of hydro­gen are dependent on the existing limited supply of natural resources,

i. e., coal, naphtha, and natural gas, which are not renewable. The mate­rials are mainly based on fluidization or gasification of coal, and refor­mation by superheated steam or from steam-iron process (3Fe + 4H2O ^ F3O4 + 4H2); these processes can be broadly classified into (a) ther­mochemical or solar gasification and (b) fast pyrolysis or other novel gasification. These processes may be totally or partly catalytic. The basic chemical principles are mostly similar to those of classical water gas: C + H2O ^ CO + H2; CO + H2O ^ CO2 + H2. Major sources of hydro­gen at present are directly or indirectly natural gas; electrolysis; pyrolytic, thermal, and superheated steam; or geothermal, solar, ocean current, ocean thermal gradient, and nuclear reactors. Biomass as a source of hydrogen as well as energy has been discussed in Sec. 1.2.