It is believed that Joseph Priestly discovered oxygen on August 1, 1774. There are two more scientists associated with this event in the world of chemistry: Lavoisier and Scheele. When they discovered oxygen, they had no idea that it was the number one most common substance on the Earth. How did the scientists manage to discover something that, under normal conditions, has no taste, color, or smell?

Oxygen is a chemically active nonmetal; it has atomic number “8” in the periodic table of D.I. Mendeleev. In 1774, Joseph Priestley conducted an experiment that required mercury oxide in a hermetically sealed vessel and a powerful lens. He directed sunlight through the lens at the mercury compound, which resulted in a gas that he called “deflogged air” and rushed to report his discovery to the French chemist, Antoine Lavoisier. The very next year Lavoisier established that the discovery was nothing but “oxygen,” an independent element, and gave it a new name. Another scientist of this trio, Karl Scheele, had actually discovered oxygen earlier than anyone else, back in 1771. But he did not publish a description of the resulting substance in his book until 1777, so Priestley is officially considered to be the first to discover it.

There are three states of oxygen: gaseous (colorless), liquid (light blue) and solid (light blue crystals). It interacts practically with all substances: it has a high ability to oxidation, provides the basis for combustion of all types of fuel, so it has a wide application in industry, in explosive works, in rocket launches. Oxygen also finds its application in medicine. It is used to enrich gas mixtures for respiratory disorders, for asthma treatment, for prevention of hypoxia. Air cylinders containing mixtures of gases of different concentrations, depending on their purpose, are used in climbing to avoid altitude sickness caused by oxygen starvation; oxygen cylinders are also used for deep diving; they are used by firemen to prevent carbon monoxide poisoning.

Even in this century, scientists keep revealing some interesting properties of oxygen. For example, in 2015, it has come to our knowledge that a simple increase in the amount of oxygen in the air activates immune system cells that kill cancer cells. This research was also confirmed in 2021. Lomonosov Moscow State University biologists, together with their foreign colleagues, revealed that most tumors develop when the body is hypoxic, i.e., does not receive enough oxygen. Human cells need oxygen for oxidative reactions and energy production in mitochondria. If there is too little oxygen in the mitochondria, these processes are disrupted.

Based on open-source materials.