Archive for May, 2015

Oxygen is the most Earth crust pervasive chemical element. In a loose condition it occurs in the air, in the bound state it is a part of water, minerals and all the substances that form the plants and animals organisms. The Earth crust oxygen aggregate quantity is almost a half of its mass (about 47% by weight). The natural oxygen consists of three stable isotopes with rough atomic weights of 16 (99.76%), 17 (0.04%) and 18 (0.2%).
In a pure form oxygen was first obtained in 1771 by Joseph Priestley (1733-1804), who threw it out of mercuric oxide. “Just as the candle burns away faster in a dephlogisticated air than usual (so he called oxygen), and we, probably, would have got through one’s own life too fast … in the pure air,” Joseph Priestley wrote in his book in 1774, p.228. In the same book, the author tells of his experiences during inhalation of oxygen and predicts this gas an important medical value.