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Who first discovered oxygen?

When was oxygen discovered?

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C. W. Scheele

Swedish apothecary

Earliest of the claimants to prepare a relatively puresample of gas

Joseph priestly

British scientist

collected the gas released by heated red oxide ofmercury.

claim to the discovery of oxygen is based upon his

priority in isolating a gas that was later recognized as adistinct species.

1774: identified the gas produced as nitrous oxide

1775: dephlogisticated air- still not oxygen

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Lavoisier Led him to oxygen after Priestleys experiments.

1777: he concluded that the gas was a distinctspecies.

*Discovering a new sort of phenomenon involvesrecognizing that something is and what is it.

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Roentgen

He noticed that a barium platinocyanide screen

at some distance from his shielded apparatus

glowed when being discharged.

The cause of the glow comes in straight lines

from the cathode ray tubes.

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*At what point in Roentgens investigation can

we say that X- rays had been discovered?

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The perception of anomaly played an essential

role in preparing the way for perception of

novelty.

X- rays opened up a new field and thus added tothe potential domain of normal science.

The decision to employ a particular piece ofapparatus and to use it in a particular way carries

an assumption that only certain sorts of

circumstances will arise.

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* Discoveries predicted by theory in advance are parts

of normal science and result in no new sort of fact.

* During the paradigm-change period, scientists usuallydevelop many speculative and unarticulated theories

that can themselves point the way to discovery.

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Electricity was said to be a fluid.

It led to an attempt of bottling the fluid byholding a water- filled glass vial andtouching the water to a conductorsuspended from an active electrostaticgenerator.

Investigators experienced severe shocks.

Leyden jar - to store electrical fluid.

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Characteristics of the Discoveries fromwhich new sorts of phenomena emerge:

The previous awareness of anomaly.

The gradual and simultaneousemergence of both observational andconceptual recognition.

The consequent change of paradigmcategories and procedures oftenaccompanied by resistance.

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Anomaly appears only against the background

provided by the paradigm.

The more precise and far-reaching theparadigm, the more sensitive it is to detectingan anomaly and inducing change.

By resisting change, a paradigm guaranteesthat anomalies that lead to paradigm changewill penetrate existing knowledge to the core.