James Richard Fromm
The end of the eighteenth century was marked by the publication of Antoine Lavoisier's textbook Elements of Chemistry; this 1787 book is the first description of chemistry that a modern chemist would find recognizable. Lavoisier, following Boyle, accepted the definition of an element as any substance which cannot be broken down into simpler substances. His list of elements included many of the common metallic and nonmetallic elements known today. It also included light and heat, which we would not now classify as elements, as well as the oxides of the alkali metals and of the alkaline earths. These oxides could not be decomposed to their respective metals prior to the electrolytic experiments of Humphrey Davy.
The description of pure compounds formed from the different elements occupied much of Lavoisier's text. These descriptions were qualitative, except for the quantitative composition of the compounds by mass and the measurements of the heat properties of the compounds and the elements. The formation of oxides, and the existence of oxygen in air, was accepted by Lavoisier, and in his book it was presented for the first time in a systematic way. Not all of Lavoisier's ideas were correct; for example, he argued that all acids contain oxygen. While many acids do contain oxygen, some do not, and as a result Lavoisier's names for compounds do not exactly match their actual structure. Nevertheless, chemists continue to use them, as we shall see in a later section.