Oxygen

Who had discovered Oxygen? 

Oxygen was discovered by the English chemist Joseph Priestley in 1774.

One other scientist Carl Wilhelm Scheele had also discovered oxygen in 1773. But Priestley is often given priority because his work was published first.

Earlier theory of combustion 

In the mid-18th century, the prevailing theory for burning a flame or breathing was that flammable materials contained a substance called “phlogiston” (from the Greek word for burn) that was released during combustion. The flame would burn as long as there was phlogiston in the material which was burning.

The same “phlogiston” theory prevailed for breathing. It went like as long as there was “phlogiston” in the body, one can breathe.

Joseph Priestley and his discovery

In 1773, while serving as the librarian and tutor in the Earl of Shelburne’s estate, Bowood House, Joseph Priestley systematically analysed the properties of different “airs” using an inverted container on a raised platform that could capture the gases produced by various experiments below it.

In a series of experiments culminating in 1774, Priestley found that “air is not an elementary substance, but a composition,” or mixture, of gases. Among them was the colourless and highly reactive gas he called “dephlogisticated (an opposite of phlogiston) air,”. Later in 1777, the great French chemist Antoine Lavoisier named it “oxygen.”

Discovery of Oxygen 

 

On August 1, 1774, Priestley conducted his most famous experiment. Using a 12-inch-wide glass “burning lens,” he focused sunlight on a lump of reddish mercuric oxide in an inverted glass container placed in a pool of mercury. The gas emitted, he found, was “five or six times as good as common air.”

In succeeding tests, it caused a flame to burn intensely and kept a mouse alive about four times as long as a similar quantity of air.

Priestley called his discovery “dephlogisticated air” on the theory that it supported combustion so well because it had no phlogiston in it, and hence could absorb the maximum amount during burning.

Later in France in 1777, Priestley told about his discovery to Antonie Lavoisier.

Lavoisier called it “oxygen” from the Greek word oxy or “acid”, literally “sharp”, referring to the sour taste of acids and – genes, “producer”, literally “begetter”, because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition.

Joseph Priestley’s other discoveries

Priestley (1733-1804)  was also credited with the invention of carbonated water and the rubber eraser. He identified a dozen key chemical compounds and wrote an important early paper about electricity.

Discoverers of  other gases

  1. Carbon dioxide – Joseph Black (in 1754)
  2. Hydrogen – Henry Cavendish (in 1766)
  3. Nitrogen – Daniel Rutherford (in 1772)
  4. Carbon Monoxide –  Joseph Priestley
  5. Neon, argon, krypton, xenon – Sir William Ramsay
  6. Helium – Pierre-Jules-César Janssen and Sir Norman Lockyer

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