Atomic number: 8
Year discovered: 1772 (by Scheele) and in 1774 (by Priestley).
Discovered by: Karl Wilhelm Scheele (1742-1786), a Swedish chemist, and Joseph Priestley (1733-1804), an English chemist.
- Leonardo da Vinci suggested that air consists of at least two different gases.
- Previously air was thought to be an element in its own right.
- He was also aware that one of these gases supported both flames and life.
- Oxygen was prepared by several workers before 1772, but these workers did not recognize it as an element.
- Joseph Priestley is generally credited with its discovery (who made oxygen by heating lead or mercury oxides), but Carl Wilhelm Scheele also reported it independently.
- Mercury, when heated in air, will form a brick-red compound, which we now call “mercuric oxide”.
- Priestley heated some of this compound in a test-tube by using a lens to concentrate sunlight upon it.
- When he did this, the compound broke up, liberating mercury, which appeared as shining globules in the upper portion of the test-tube.
- In addition, a gas was given off that possessed most unusual properties.
- Combustibles burned more brilliantly and rapidly in it than they did in ordinary air.
- Mice placed in an atmosphere of this gas were particularly frisky, and Priestley himself felt “light and easy” when he breathed it.
- When French chemist Antoine-Laurent Lavoisier (1743-1794) heard of the experiments of Priestley and British chemist Daniel Rutherford (who discovered a new gas that eventually came to be called “nitrogen”); he realized in the light of his own experiments that air must consist of a mixture of two gases.
- One-fifth was Priestley’s gas, which Lavoisier named oxygen (from the Greek words meaning “acid producer”, because it was mistakenly felt at the time that all acids contained oxygen).
- Four-fifths were Rutherfords’ gas, which Lavoisier named “azote” (from Greek words meaning “no life”), but which later came to be known as nitrogen.
- It seemed obvious that it was oxygen that supported combustion and animal life and oxygen that was involved in rusting.
- Animals must consume oxygen and produce carbon dioxide, and from Priestley’s earlier experiment, plants must consume carbon dioxide and produce oxygen.
- In a classic case of scientific misfortune, the Swedish chemist Carl Wilhelm Scheele had discovered oxygen at least two years before Priestley did, and by the same method.
- Why didn’t Scheele get the credit for the discovery? Because it wasn’t published (through the negligence of a publisher) until after Priestley’s discovery had been reported, so Priestley got the credit.
- With these two forms of life, the atmosphere tends to maintain a stability and balance.
- The discovery that air, invisible air, was “something” and not “nothing” profoundly altered how all scientists thought.
- Joseph Priestly is quoted as saying, “We cannot solve one doubt without creating several new ones.”
- The behavior of oxygen and nitrogen as components of air led to the advancement of the phlogiston theory of combustion, which influenced chemists for a century or so, and which delayed an understanding of the nature of air for many years.
- Phologiston is a hypothetical substance formerly thought to be a volatile constituent of all combustible substances released as flame in combustion.
Name in other languages:
Information about other elements may be seen at this Chemical Elements List.
A special unit about words that include chemo-, chem- may be seen here.