The discovery of oxygen stands as one of the most transformative milestones in the history of science. It not only reshaped humanity’s understanding of air and combustion but also marked a pivotal moment in the Scientific Revolution—a period that fundamentally changed the way people viewed the natural world. This article explores the events leading up to the discovery of oxygen, the scientists involved, and the wide-ranging effects this breakthrough had on chemistry, medicine, industry, and scientific thinking.
The Scientific Climate Before the Discovery
Before the 18th century, the dominant theory of combustion was known as the phlogiston theory, developed in the late 1600s. According to this idea, all combustible materials contained a substance called phlogiston, which was released during burning. A material that burned and left behind a residue was thought to have lost its phlogiston. While this theory attempted to explain phenomena like rusting and combustion, it faced growing inconsistencies that puzzled scientists.
Despite these shortcomings, phlogiston theory remained popular because it aligned with observations of the time. For instance, metals appeared to gain mass when they rusted—a contradiction, since losing phlogiston should theoretically make them lighter. However, without an understanding of gases and the composition of air, there was no solid framework to challenge this view effectively.
The stage was thus set for a major paradigm shift, one that would begin with the isolation and identification of a previously unknown component of air—oxygen.
Joseph Priestley and the Early Discovery
In 1774, English chemist and clergyman Joseph Priestley conducted a series of experiments in which he heated mercuric oxide (HgO) with sunlight using a magnifying glass. This process released a gas that made a candle burn brighter and allowed mice to live longer when placed in a closed container filled with it. Priestley had effectively isolated oxygen, though he referred to it as “dephlogisticated air” because he was still working within the framework of the phlogiston theory.
Priestley’s experiments were meticulous, and his findings quickly caught the attention of the European scientific community. Though he had discovered oxygen, he did not fully understand its chemical nature. Nonetheless, his work laid the groundwork for others to build upon. His methods demonstrated the importance of experimentation and provided a reproducible approach to gas collection and analysis.
Antoine Lavoisier and the Fall of Phlogiston Theory
While Priestley discovered oxygen, it was the French chemist Antoine Lavoisiers who gave it its name and correctly interpreted its role in combustion. After reading Priestley’s work and conducting his own experiments, Lavoisier concluded that burning was not the release of phlogiston but rather a chemical reaction involving oxygen.
Lavoisier demonstrated that when a substance burns, it combines with oxygen from the air to form a new compound. For example, when sulfur burns, it forms sulfur dioxide; when iron rusts, it forms iron oxide. This was a complete reversal of the phlogiston concept. In 1777, he proposed the term “oxygen,” derived from Greek words meaning “acid former,” because he incorrectly believed that all acids contained oxygen.
Perhaps more significantly, Lavoisier established a new approach to chemistry based on precise measurements and clear terminology. He helped create the modern system of chemical nomenclature and emphasized the importance of mass conservation in reactions, stating that matter is neither created nor destroyed. His book, Elementary Treatise of Chemistry (1789), is often considered the first modern chemistry textbook.
Impacts on Medicine and Physiology
The discovery of oxygen had profound effects beyond chemistry, particularly in the fields of medicine and physiology. Scientists began to understand that oxygen was essential for respiration. Early studies revealed that animals and humans take in oxygen and give off carbon dioxide—a realization that helped clarify how the lungs function and how energy is produced in living organisms.
This knowledge also led to practical applications in medical treatment. By the early 19th century, physicians began experimenting with oxygen therapy, using it to treat conditions like asthma, heart failure, and respiratory diseases. Though early treatments were rudimentary, they marked the beginning of respiratory medicine as a field.
Additionally, understanding the role of oxygen in cellular processes laid the foundation for modern biochemistry. Today, concepts like aerobic respiration, oxidative stress, and metabolism all stem from the original identification and study of oxygen.
Oxygen’s Industrial and Technological Legacy
Beyond the laboratory and clinic, the discovery of oxygen also catalyzed progress in industrial chemistry and manufacturing. The realization that combustion is a chemical reaction involving oxygen allowed for more efficient design of furnaces, engines, and chemical reactors.
One of the most immediate benefits was in the steel industry, where controlled oxygen flows improved smelting processes, enabling the mass production of high-quality steel. Oxygen also became integral in processes like the Bessemer and later the basic oxygen process, which revolutionized steelmaking in the 19th and 20th centuries.
In addition, oxygen was crucial in the development of rocket propulsion and space exploration in the 20th century. Liquid oxygen serves as a key oxidizer in rocket engines, making space travel possible. These applications show how a scientific discovery from the 18th century continues to shape modern engineering and technology.
A Catalyst for Scientific Method and Enlightenment Thinking
Finally, the discovery of oxygen contributed to a broader cultural and intellectual transformation. It helped usher in a new era of scientific inquiry grounded in empirical evidence, skepticism of authority, and collaborative research. The fall of the phlogiston theory is often cited as one of the earliest examples of a scientific revolution as defined by philosopher Thomas Kuhn—a fundamental shift in the basic concepts and experimental practices of a scientific discipline.
Lavoisier’s emphasis on precision, measurement, and terminology influenced generations of scientists and helped define the modern scientific method. The revolution in chemistry also mirrored the Enlightenment’s values of reason, progress, and the power of human understanding. Oxygen, in this sense, became not just a chemical element but a symbol of intellectual liberation.
