Oxygen was for the first time open the scientist D. Priestley in 1774 at mercury oxide decomposition. Originally English chemist did not understand that he managed to allocate, and he called the received gas deflogistirovanny air. Later the scientist A. Lavoisier established that O2 is composition of the atmosphere and contains in many substances.
In industrial conditions oxygen is received generally by method of cryogenic ratification or in special membrane installations today. This gas in laboratories, medical institutions and on productions usually in tanks from steel is delivered with a pressure of 15 MPas.
Smell and other characteristics
With a usual atmospheric pressure oxygen represents gas without taste, color and a smell. In water and alcohol it is dissolved rather poorly, and in the melted liquid silver it is very good.
One of features of O2 is that it is very strong oxidizer. Oxygen forms oxides practically with all known elements. At the same time reactions of this kind are capable to accelerate when heating and always proceed with allocation of heat.
Smell and color in special states
At compression up to 50 atm and cooling in -119 °C oxygen turns into liquid state. With a usual atmospheric pressure for such transition of O2 it is necessary to cool up to -183 °C. At a temperature in — 220 °C oxygen hardens in snegoobrazny weight.
Liquid and solid oxygen, as well as gaseous, has no smell. O2 color can change considerably depending on its temperature. In liquid state oxygen differs in slightly bluish shade.
At further cooling O2 color becomes more and more saturated. Crystals of solid oxygen already have rich blue color. At increase in pressure they at first become pink, and then orange and dark red.
With a pressure of 96 GPa the crystals of oxygen get a metal shade. Strong cooling in this case causes also effect of superconductivity.
Ozone
Color, thus, has oxygen only in liquid and strong state. It has no smell any at all. A little in a different way the situation is with his closest relative — the ozone consisting of three molecules of molecular oxygen.
Unlike oxygen, ozone in gaseous state has bluish color. At this O3 and rather sharply smells. A smell at ozone pretty pleasant. We feel it, for example, after a rain.
During bad weather air contains usually 10% or slightly more ozone. The person cannot inhale clean O3. It will lead to division of cages and leak enzymes from them.