Between air and oxygen, the story of the discovery that developed the concepts of chemistry

Oxygen is one of the most important natural elements on which different types of living organisms depend for the purpose of breathing. Despite this importance, chemists did not discover this element until nearly 250 years ago.

Oxygen is a gas that has no taste, smell or color. It is the most available element on the planet after hydrogen and helium. It represents about 21% of the components of the atmosphere, and 89% of sea water.

The American Chemical Society believes that the English chemist Joseph Priestley was the first to discover oxygen in August of 1774, when he conducted an experiment that involved heating mercury oxide red in color, resulting in a colorless gas.

The Journey of Discovering the Element of Air

The ancient Greek philosophers contributed to clarifying the concept of the atom, and they established the belief that all things in the universe are divided into small units that they called elements (Elements), and Aristotle pointed out that all materials in the universe include one or more of those four elements: air, water, fire and earth. , which means that they treat "air" as a single element that does not contain a number of gases.

Later, the Greek scientist "Philo of Byzantine" conducted an important experiment that changed many concepts about the nature of "air." The steps of that experiment were described in Chapter Eight of the book (Pneumatica), a Latin word meaning "mechanical science", written by the Greek engineer and physicist Heron. Alexandria (Heron of Alexandria).

To conduct the experiment - which he called the burning candle experiment - "Philo" used a bowl, a candle, and a thin inverted glass jar, and fixed this candle inside the bowl, then filled it with water, lit the candle, and then covered it with the glass bowl that touches the surface of the water, and after some time The candle is extinguished and the water level inside the glass vessel rises. Philo explained this by the disappearance of air from the vessel as a result of the candle burning, and the water occupying the space from which the air was emptied.

Chemists arrive at the phlogiston theory

Experiments based on the Byzantine Philo theory continued to be carried out. The well-known painter and polymath Leonardo da Vinci noticed the consumption of part of "air" during respiration or burning, which was later confirmed by more researchers.

In 1669, the German chemist Johann Joachim Becker indicated that materials include 3 types of "earth", namely: verifiable, mercury, and combustible, and explained that burning materials leads to Production of the flammable earth element, an element that chemist George Ernst Stahl named: Phlogiston, a Greek word meaning "burned".

To clarify the theory, it can be said that wood material contains two components: phlogiston and ash, and burning wood releases phlogiston and only ash remains.

Discovery of oxygen gas

Joseph Priestley conducted his most famous experiment by using a lens with a diameter of about 30.5 centimeters and directing sunlight to a mass of mercuric oxide contained in an inverted glass container placed in a basin filled with mercury.

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That experiment resulted in the emission of a gas that Priestley described as “5 or 6 times better than conventional air.” And through some experiments, exposure to that gas increased the intensity of the flame’s combustion, and helped mice live 4 times longer than they were exposed to the same amount of conventional air. Priestley called that gas (Dephlogisticated air), or phlogiston-free air.

In the following October, Priestley traveled to several countries, including France, where he met the chemist Antoine Lavoisier, who told him about the results of his experiments. and breathing, and given its current name "oxygen".

Although Priestley had previously discovered oxygen, several sources indicate that the Swedish scientist Carl Wilhelm Shelley was able to separate oxygen through experiments similar to what Priestley conducted experiments that relied on burning some materials and observing the emissions resulting from those processes, and these experiments were conducted in 1771, but Its results were not published until 1777.

The discovery of oxygen and the identification of its properties contributed to several industrial developments related to the development of the concept of "combustion", which in turn helped in the development of steam engines and the emergence of the industrial revolution.