Table of Contents
- Introduction
- Before Oxygen: The Age of Phlogiston
- Who Was Carl Wilhelm Scheele?
- The 1774 Discovery in Sweden
- How Scheele Found “Fire Air”
- Joseph Priestley and the Parallel Discovery
- Lavoisier and the Final Naming
- Why Was Oxygen So Important?
- The End of Phlogiston Theory
- The Birth of Modern Chemistry
- Oxygen in Combustion and Respiration
- Immediate Scientific Impacts
- Industrial and Technological Uses
- Scheele’s Legacy and Tragedy
- Conclusion
- External Resource
- Internal Link
1. Introduction
We breathe it every second without thinking. It powers fire, fuels our cells, and supports almost all life on Earth. But for most of human history, oxygen was a complete mystery.
It wasn’t until August 1, 1774, in a modest Swedish laboratory, that Carl Wilhelm Scheele conducted an experiment that would forever change how we understood air, fire, and life itself.
While the discovery of oxygen is often associated with multiple names, Scheele’s role remains a vital—and often overlooked—chapter in the story of modern chemistry.
2. Before Oxygen: The Age of Phlogiston
Before oxygen, scientists believed in the phlogiston theory. This odd hypothesis suggested that everything that could burn contained an invisible substance called phlogiston. When something burned, it released this substance into the air.
In retrospect, it sounds bizarre—but at the time, it fit the available evidence. That is, until the discovery of oxygen completely dismantled it.
3. Who Was Carl Wilhelm Scheele?
Scheele was a Swedish-German pharmacist and chemist, born in 1742. Largely self-taught, he worked in pharmacies where he would conduct groundbreaking experiments after hours.
Scheele’s curiosity and perseverance were legendary. He discovered or isolated several substances before many better-known scientists, including chlorine, manganese, glycerol, hydrogen fluoride, and more.
But his most important discovery? A strange type of air that made candles burn brighter.
4. The 1774 Discovery in Sweden
In Köping, Sweden, on August 1, 1774, Scheele heated mercuric oxide and a few other compounds. He noticed that the resulting gas could sustain combustion better than normal air.
He called this new substance “fire air” because flames roared to life in its presence. Unlike phlogiston theory, this gas seemed to be adding something to the fire—not taking something away.
He had just identified oxygen, though he didn’t know the name yet.
5. How Scheele Found “Fire Air”
Scheele’s process involved heating materials that released gases. By carefully capturing and observing how those gases interacted with flames and living things, he noted several crucial facts:
- Mice survived longer in fire air.
- Candles burned brighter.
- Metals calcinated more effectively.
He wrote all this down in his manuscript “Chemical Treatise on Air and Fire”, but publication delays would cost him priority.
6. Joseph Priestley and the Parallel Discovery
Just days after Scheele’s experiments, Joseph Priestley, an English theologian and chemist, independently performed a similar experiment.
Priestley also heated mercuric oxide, capturing the same gas. He published his findings quickly and is often credited with the discovery of oxygen.
Ironically, Scheele discovered it first, but Priestley beat him to publication.
7. Lavoisier and the Final Naming
Enter Antoine Lavoisier, a brilliant French chemist. He read Priestley’s work, repeated the experiments, and realized the phlogiston theory made no sense.
Lavoisier named the gas “oxygène” from the Greek oxys (acid) and genes (producer), believing incorrectly that oxygen was present in all acids.
Though Lavoisier didn’t discover oxygen, his refutation of phlogiston and establishment of modern chemical nomenclature sealed oxygen’s place in science.
8. Why Was Oxygen So Important?
Oxygen changed everything in chemistry:
- It disproved the phlogiston theory
- It helped define elemental reactions
- It introduced the idea of conservation of mass in reactions
- It led to the development of stoichiometry and molecular theory
This wasn’t just another element. It was the key to unlocking how matter interacts.
9. The End of Phlogiston Theory
With oxygen’s discovery and proper identification, the phlogiston theory crumbled. It simply couldn’t explain the behavior of combustion or respiration in the presence of oxygen.
For the first time, scientists began to understand that burning involved combining with oxygen, not releasing an imaginary substance.
This moment marks the end of mystical alchemy and the birth of rational chemical science.
10. The Birth of Modern Chemistry
The oxygen breakthrough ushered in a new era. Chemistry transformed from qualitative guesswork into a quantitative science. Lavoisier’s work, combined with Scheele and Priestley’s discoveries, laid the groundwork for:
- Chemical equations
- Atomic theory
- Molecular bonding
These advances would eventually lead to organic chemistry, pharmaceuticals, and even biochemistry.
11. Oxygen in Combustion and Respiration
Further studies proved that oxygen was essential not just for burning wood—but for human life.
- In combustion, it reacts with carbon to produce CO₂ and heat.
- In respiration, it enables cells to convert glucose into energy.
- In industry, it accelerates metal smelting, rocket propulsion, and medical therapies.
Suddenly, air was no longer empty—it was alive with function.
12. Immediate Scientific Impacts
Scheele’s oxygen led to rapid developments:
- Safer mining using flame lamps in oxygen-rich environments
- Medical oxygen therapy
- Use in glassmaking, metallurgy, and chemicals
- Fundamental advances in biology and anatomy
Every aspect of science—from geology to neuroscience—now leaned on this invisible, odorless gas.
13. Industrial and Technological Uses
In the modern world, oxygen is used in:
- Welding and metal cutting
- Rocket engines (as a propellant oxidizer)
- Ventilators and anesthesia machines
- Steel production
- Aquaculture and water treatment
From ICUs to outer space, Scheele’s discovery fuels progress.
14. Scheele’s Legacy and Tragedy
Scheele’s brilliance came at a cost. He worked without protective gear, inhaling and ingesting many chemicals. He died young, at 43, possibly from exposure to toxic compounds.
Though he never got the fame of Lavoisier or Priestley, many scientists revere Scheele as one of chemistry’s true unsung heroes.
His oxygen discovery remains one of the most important in all of science.
15. Conclusion
On August 1, 1774, Carl Wilhelm Scheele peered into a retort and discovered a gas that would disprove centuries of faulty science and give birth to a new age of chemistry.
The discovery of oxygen not only reshaped science—it reshaped our understanding of life itself. Every breath we take is a reminder of that quiet moment in a Swedish lab when the world began to truly understand air.
16. External Resource
Wikipedia – Carl Wilhelm Scheele
