Discovered
Oxygen was discovered by the Swede Scheele and the Englishman Priestley independently of each other during the late 18th century. For most of the 18th century, it was considered that a volatile substance, phlogiston, was emitted during all combustion. When the French chemist Lavoisier showed that metals increased their weight during combustion, those who believed in the phlogiston theory were forced to assume that phlogiston had a negative weight. Reluctantly, the phlogiston theory was abandoned
Characteristics
Oxygen, O2, lacks color, odor and taste. Liquid oxygen has a pale blue color and is paramagnetic, which means that it is weakly attracted to a magnet. Ozone, O3, which can be formed by electrical discharges or by ultraviolet light on oxygen, is chemically very active. The ozone layer found in the upper part of the atmosphere is of great importance for life on earth because it prevents large parts of the dangerous ultraviolet radiation from reaching the earth’s surface. Ozone is very toxic. The limit value in air is 0.2 mg / m3. Liquid ozone is bluish and solid ozone is black-violet. Natural oxygen is a mixture of three isotopes. Nine isotopes are known.
Use
Part of hundreds of thousands of associations. Oxygen is important for plants and animals and for practically all combustion.
Presence
Oxygen is the most common element in the earth’s crust — about 49% by weight. In the sun, oxygen is the third substance after hydrogen and helium. The sun’s red and yellow-green aura comes from oxygen. About 2 thirds of our body and 90% of water is oxygen.
Production
The plants release almost all the oxygen on earth. In the laboratory, oxygen can be produced by electrolysis of water or by heating potassium chlorate with magnesium dioxide as catalyst.
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