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1.4.2 - Oxygen O2

Oxygen is a colourless, combustion promoting, odourless gas and is extraordinarily reactive in molecular form while forming compounds with nearly all elements. It is therefore, of biological importance. Oxygen forms an important nutritive substance and is essential for sustaining the life of the overwhelming majority of organisms. Only a few kinds of bacteria (anaerobes) can live entirely without oxygen. An adult human consumes daily, about 900g of oxygen, from the air. In addition, 225g must be taken up from nourishment in chemically combined form. The human lung can just about utilise oxygen poor mixtures with 8-9% oxygen, breathing in gas mixtures with only 7% oxygen causes loss of consciousness after some time and an even lower content leads to inevitable suffocation. In industry, oxygen is generated predominantly from liquid air through fractional distillation and condensation and is traded in blue coloured steel bottles at 200 bar. Oxygen is frequently used instead of air for combustion and oxidation processes, likewise in metallurgy and metal working, as well as for autogenous welding and cutting. Oxygen is also used for manufacturing sulphur and sulphuric acid in the chemical industry.