ABSTRACT
So long as chemical processes had their explanation in the phlogiston theory, it was certainly possible to offer a provisional explanation of a number of phenomena in the sphere of combustion and oxidization, but any deeper insight into the material changes which both animate and inanimate nature daily undergo was of course out of the question. In particular the qualitative side of the chemical process was, as far as this theory went, inexplicable. In spite of this, the theory was stubbornly maintained during the greater part of the eighteenth century, doubtless because so many discoveries had been made under the assumption of its correctness, which the chemists hesitated to interpret anew. For the rest a more accurate knowledge of the process of combustion presupposed a knowledge of the types of gas that play a part therein, and this knowledge was not acquired until the latter half of the eighteenth century. The progress made in this field of inquiry is primarily bound up with three names: the Englishmen Priestley and Cavendish, and the Swede Scheele. Priestley deserves still further mention as a discoverer in the biological sphere; Cavendish (1731-1810) is best known as the discoverer of hydrogen, and Scheele (1741-86), one of the most brilliant experimental scientists of all time, succeeded in making, in spite of his short life, a large number of chemical discoveries, his treatise On Air and Fire becoming especially famous.
