LAVOISIER, PRIESTLY, and the ELEMENTS by Elizabeth Edersheim

“Becher postulated the existence of a fire-like element called ‘phlogiston’, which was contained within combustible bodies and released during combustion. The theory was an attempt to explain processes of burning such as combustion and the rusting of metals, which are now collectively known as oxidation. Once burned, the ‘dephlogisticated’ substance was held to be in its ‘true’ form, the calx.

What do we do when the facts as we understand them don’t add up? In the 1770s, burning was explained by a theory about a fire-like element called ‘phlogiston’ contained within combustible materials and released during combustion When something burned, it ‘dephlogistacted.’

When Priestly studied something he stuck to his theory.

Priestly effectively discovered Oxygen, but would not call it an element. He did some experiments and saw that a candle in a sealed jar went out, a mouse in a sealed container died, and yet a plant continued living in the container. He insisted on sticking with the theory, which holds that all combustible materials contain phlogiston, a substance without color, odor, taste or mass, and is liberated in burning. Until the day he died, he refused to entertain any alternatives.

LaVoisier Antonie, a French scientist and credited with being the father of chemistry, saw the same facts of the mouse and the plant. When he weighed burning substances, though, he realized that in combustion something in the air was being used up. Abandoning notions of phlogiston, he recognized it was a separate element, which he named it Oxygen.

At the height of the French Revolution, LaVoisier was guillotined by a judge who distrusted scientists.

In building the periodic table a hundred years later, Mendeleev knew oxygen existed. ‘Theories without facts are castles in the air. . . Facts without theories are useless matter,’ he remarked. ‘Priestly had both.’”