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Early Research on Air Early research on air was rarely done by many scientists of any field because of their misunderstanding of its composition. The composition of air has fascinated scientists since early times. According to the ancient Greeks, air was regarded as one of the four elements, which also included fire, earth, and water. It was not, however, precisely studied or correctly understood by many scholars. They generally thought that the air people breathe had the same composition as the gases found in any other part of the universe. Eventually, a few analytical scientists began to question its properties and conducted research to define them, but their studies were limited by the fact that they only sought to study air in the perspective of their specialties. Prior to the seventeenth century, chemists believed that gases were not involved in chemical reactions, and focused on matter in its solid or liquid states: according to them, gases were in the domain of physicists. This trend significantly impeded progress on the study of air. It was not until the seventeenth century that the understanding of air was seriously pursued by scientists. However, due to the lack of scientific instruments and the need for those beyond the usual tools, their experiments soon faced limitations. For example, Robert Boyle, a British scientist known for Boyle’s Law, began a series of experiments to find out the composition of air through combustion. Boyle vacuumed the air out of a jar and showed that neither charcoal nor sulfur burned in the vacuum. Boyle had discovered the very first property of air stating that it is required for a fire to burn. His finding was not, however, recognized by the scientific community of the day because his definition of the component of air responsible for combustion was vague. In addition, most scientists were reportedly more interested in finding the chemical composition of air than in its physical characteristics. Thus, he shifted the focus of his research to air's chemical aspects and in 1659, with continuous effort, discovered that both hydrogen and nitric oxide gases were present in air. Boyle also tried to revise misconceptions regarding air, such as the popular belief that air had no weight. Years later, Einstein credited Boyle for having a holy curiosity in poorly understood phenomena that others simply accepted as ‘natural’. As a result of his persistence, he is now known as the father of chemistry. Even with all of Boyle’s achievements, people’s understanding of air was still elementary and more study using advanced laboratory equipment was required. Scientists still struggled to uncover the many unknown properties of air, which were exemplified by the rudimentary definition of air as ‘the elastic, invisible mixture of gases that surround the earth’ from an eighteenth century encyclopedia. Its invisibility meant that it could not be observed under a microscope and its ability to diffuse quickly proved to be an irritable characteristic to scientists for it complicated calculations measuring the amount of air being experimented upon. Therefore, many prominent physicists investigated air wishing to further their understanding, but they showed little noticeable progress; having no success in isolating even one of the many compounds in air. Luckily, the research on air was significantly advanced by Stephen Hales, an English physiologist and chemist, in the late eighteenth century. In search of the various properties of air and anxious to clearly define it, he gave birth to a new branch in chemistry called pneumatic chemistry. He invented the pneumatic trough to study the physical properties of air and their relation to chemical reactions. The trough was made from household objects such as a hunting gun and a glass vessel. The device measured the amount of gas produced when a substance was heated by measuring the amount of water displaced in the vessel. Hales’ pneumatic trough became the basis for experimental instruments that are widely used today. The creativity demonstrated through his improvisation of turning common tools into useful scientific instruments was recognized by, and won the praise of, fellow scientists. According to the scientific community, however, Hales deserves more recognition than he received in the past as experiments regarding air were actively held by scientists of various fields using his invention. Despite his tremendous contributions to pneumatic chemistry, Hales passed up the opportunity to study the chemical properties of the various gases, as he was solely interested in studying their concentrations. Scientists that came after him revised his pneumatic trough and proceeded with further experiments. With the efforts of these scientists, the properties of the air have been gradually unveiled. They have even successfully broken down all of the components of atmospheric air and calculated their proportions.