Joseph-Louis Proust Essay

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Joseph-Louis Proust was a French Chemist, born September 26th, 1754 and died July 5th, 1826 (1). He was made famous for his contribution in the creation of Proust’s Law—also known as Law of Definite Proportions—which determined, “relative quantities of any given pure chemical compound’s constituent elements remain invariant, regardless of the compound’s source” (1). Proust believed, “chemical compounds are composed of a fixed ratio of their constituent elements irrespective of the methods of production” (2). At the time of his publication (1794), this was not a widely accepted notion. Claude-Louis Berthollet was Proust’s major opponent, which stirred a famous debate. Berthollet disagreed with Proust, thinking, “the elements could combine in any proportion” (2). The debate between Proust and Berthollet went on for several years. Although Proust would eventually be proved correct, Berthollet’s authority partly hindered the acceptance of Proust’s theory. Another problem was Proust’s inability to completely articulate why the reagents behaved the way they did. In the years following, other experiments would support Proust’s theory, which would ultimately become accepted by the scientific community and be known as Proust’s Law in his honor. In 1803, John Dalton supported for Proust’s theory by providing the rationale for why elements behaved this way in his atomic theory. Dalton’s theory concluded that, “a fixed number of atoms of one substance always combined with a fixed number of atoms of another substance in forming a compound” (1). Dalton offered an extension of Proust’s Law, known as the Law of Multiple Proportions or Dalton’s Law, which stated that: in situations in which elements can combine to form multiple combinations, the ratio of the elements in those compounds can be expressed as small whole numbers (3). Proust’s Law was further solidified by Jöns
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