Herewith an exchange between Francis Franck and Chatbot concerning Drebbel and oxygen. '''''Did Cornelis Drebbel produce oxygen?''''' Cornelis Drebbel did not produce oxygen, as oxygen was first discovered and identified by Swedish chemist Carl Wilhelm Scheele in 1772, long after Drebbel's time. However, Drebbel did make significant contributions to the field of chemistry and experimental science during the 17th century. Drebbel was a Dutch inventor and natural philosopher who is best known for his work in optics, alchemy, and the construction of the first navigable submarine. He also worked on creating artificial light and improving the air supply in enclosed spaces such as mines, ships, and buildings, which may have involved the production of gases such as carbon dioxide. However, the discovery and identification of oxygen came after his time, and he did not have access to the tools and knowledge necessary to produce or identify the gas. '''''It wasn't called oxygen in Drebbel's time but he produced a "fiery spirit" to permit the survival of people in his submarine,''''' You are correct that while the gas we now know as oxygen was not identified or named during Drebbel's time, he did work on improving air quality in enclosed spaces and may have produced what he called a "fiery spirit" that allowed for the survival of people in his submarine. Drebbel's submarine, which he built in the early 17th century, was an enclosed vessel that was designed to navigate underwater. In order to keep the crew alive during long periods of submersion, Drebbel developed a system that circulated air and replenished the oxygen supply inside the vessel. It's unclear exactly what methods he used to produce the "fiery spirit," but it's possible that he used a chemical reaction to generate oxygen, which would have provided the crew with a source of breathable air. While the term "oxygen" did not exist in Drebbel's time, his work on air quality and the development of his "fiery spirit" were important early steps in the study of gases and the understanding of their role in supporting life. '''''We suppose that Drebbel was using potassium nitrate to produce oxygen.''''' It's possible that Cornelis Drebbel used potassium nitrate (also known as saltpeter) to produce oxygen for his "fiery spirit" in his submarine. Potassium nitrate is a common source of oxygen, and it has been used for various purposes throughout history, including in the manufacture of gunpowder and in early experiments with combustion. Drebbel's actual methods for producing oxygen are not well-documented, so it's difficult to say for certain what chemicals or reactions he used. However, it is known that he was interested in alchemy and in the transmutation of substances, so it's possible that he experimented with a variety of chemical reactions to produce the gases he needed for his various projects. Regardless of the specific methods he used, Drebbel's work on air quality and gas production was an important early step in the development of modern chemistry, and it laid the groundwork for later discoveries in the field.