Lavoisier was concerned with improving the lives of the public, and the origin of his discoveries about elements began with a project in to improve the supply of good drinking water in French cities.
At the time, there was no effective method for measuring the quality of water chemically, so he had to rely on measuring the density, a physical measure. To better understand the process, he created an experiment to learn more. By heating an amount of distilled water in a sealed container over days, he found that the weight of the container had not changed. Despite his eminence and his services to science and France, he came under attack as a former farmer-general of taxes and was guillotined in But alongside familiar superhuman avengers were other kinds of heroes: real-life chemists.
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Audra J. War left a lasting impression on early American chemist James Woodhouse. For one thing, it showed him that doctors needed a proper understanding of chemistry to save lives. Joseph Priestley — theologian and natural philosopher. Henry Cavendish — natural philosopher. See all related overviews in Oxford Reference ». French chemist, who collected taxes for the government in Paris.
In the s he discovered oxygen and nitrogen in air and demolished the phlogiston theory of combustion by demonstrating the role of oxygen in the process. In he made water by burning hydrogen in oxygen see Cavendish, Henry.
He also devised a rational nomenclature for chemical compounds. Unlike physics, which had come of age through the work of Isaac Newton a century earlier, chemistry was still mired in the legacy of the Greek philosophers. The four elements of Aristotle — earth, air, fire, and water — had been slowly modified by the medieval alchemists, who added their own arcane language and symbolism.
Thrown into this mix was the concept of phlogiston. Developed by the German scientist Georg Ernst Stahl early in the 18th century, phlogiston was a dominant chemical concept of the time because it seemed to explain so much in a simple fashion. Stahl believed that every combustible substance contained a universal component of fire, which he named phlogiston, from the Greek word for inflammable. Because a combustible substance such as charcoal lost weight when it burned, Stahl reasoned that this change was due to the loss of its phlogiston component to the air.
It followed that the less residue a substance left after burning, the greater its phlogiston content. Turning from organic substances to metals, Stahl knew that a metal calx known today as an oxide heated with charcoal formed the original metal.
He proposed that the phlogiston of the charcoal had united with the calx. Therefore, metals, which were thought to contain phlogiston, were also classified as combustibles. The difficulty with this scheme was the reverse reaction. When metals were strongly heated in air, the resulting calx weighed more than the original metal, not less, as would be expected if the lead had lost the phlogiston component.
This inconsistency caused some phlogistonists to suggest that phlogiston might even have a negative weight. By , having abandoned law to pursue a career in science, Lavoisier turned his curiosity to the study of combustion.
The importance of the end in view prompted me to undertake all this work, which seemed to me destined to bring about a revolution in…chemistry. An immense series of experiments remains to be made. In experiments with phosphorus and sulfur, both of which burned readily, Lavoisier showed that they gained weight by combining with air.
With lead calx, he was able to capture a large amount of air that was liberated when the calx was heated. To a suspicious Lavoisier, these results were not explained by phlogiston. Although Lavoisier now realized that combustion actually involved air, the exact composition of air at that time was not clearly understood.
He described how he had recently heated mercury calx a red powder and collected a gas in which a candle burned vigorously. Priestley believed his "pure air" enhanced respiration and caused candles to burn longer because it was free of phlogiston. In Paris, the intrigued Lavoisier repeated Priestley's experiment with mercury and other metal calces. He eventually concluded that common air was not a simple substance.
Instead, he argued, there were two components: one that combined with the metal and supported respiration and the other an asphyxiant that did not support either combustion or respiration.
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