47. Oxygen

Experiments and observations on different kinds of air / by Joseph Priestley. (London : printed for J. Johnson, 1774-1777) 3 vols.

Joseph Priestley was born near Leeds in 1733. He was educated as a minister but early began to show aptitude for science. After beginning as a preacher, he accepted a teaching position at Warrington Academy where he became actively engaged in natural philosophy (physics) and chemistry. In 1765 he visited London where he met Benjamin Franklin. As a result of his experiments on electricity Priestley was elected Fellow of the Royal Society (FRS) in June 1766. Among other things he discovered that charcoal (carbon) is an excellent conductor of electricity, a simple discovery that has had wide applications in science and technology.

In 1767 he became minister at Mill-Hill Chapel in Leeds, where his first residence was near a brewery. Priestley was fascinated by the ‘fixed air’ (carbon dioxide) that bubbled up and cascaded down the sides of the vats; he collected some of this ‘fixed air’ and experimented with it. An important outcome of this was the development of soda water or carbonated water, pure water saturated with carbon dioxide; this soon became a very popular drink; the Lords of the Admiralty ordered that carbonated water be available on the vessels for Cook’s second voyage to the Pacific.

In November 1773 Priestley was awarded the prestigious Copley Medal by the Royal Society for his experiments on “different kinds of air”, i.e. gases.

In August 1774 Priestley made his most momentous discovery – oxygen - named by him as “dephlogisticated air”. But Priestley failed to understand the real significance of his discovery. His failure was implicit in the name “dephlogisticated air”, based on the almost century-old phlogiston theory.

These volumes hold a very important place in the history of science. The fold-out frontispiece of Volume 1 shows Priestley’s apparatus for collecting and testing gases; an earthenware oval-shaped pneumatic trough was filled with either water or mercury, and the gases were collected by displacement of the liquid in inverted cylindrical glass vessels. His use of mercury for collection of gases that would react with water was an important new development.

Elements of chemistry, in a new systematic order, containing all the modern discoveries ... / by Mr. Lavoisier. Translated from the French by Robert Kerr. 4th ed. : with notes, tables, and considerable additions. (Edinburgh : Printed for William Creech; and sold in London by G.G. & J. Robinson, and T. Kay, 1799)

The first (French) edition, Traité élémentaire de chimie, présenté dans un ordre nouveau et d’après les découvertes modernes, was published in Paris in 1789.

This volume constitutes an important landmark in the science of chemistry. Indeed, it may be claimed that Lavoisier’s Traité élémentaire de chimie was to the development of chemistry at the end of the eighteenth century as Newton’s Principia was to the enlightenment in mathematical physics and celestial mechanics a century earlier.

In October 1774 Priestley was in Paris and he described to Antoine Lavoisier his experiment that produced the new “dephlogisticated air”. Lavoisier already had experimental evidence that had made him sceptical of the phlogiston theory. He repeated Priestley’s experiment, but quantitatively, and found that the weight lost in the conversion of mercury calyx (oxide) to metallic mercury equalled the weight of the gas produced; he called the new gas oxygène (oxygen).

Although not the first man to prepare (discover) pure oxygen, Lavoisier was the first to understand its nature and to explain the true nature of oxidation and reduction. Lavoisier removed the mystical ‘veil’ of phlogiston, and his Traité élémentaire de chimie set the stage for real progress in the science of chemistry.