Joseph Louis Proust GROUP 10

Joseph Louis Proust
Born: September 16, 1754
         Angers, France
Studied Chemistry in his father's shop
Gained the appointment of apothecary in chief to the Salpetriere
Taught chemistry with Pilatre de Rozier, A famous Astronaut
Died: July 5, 1826
        Paris. France (age of 71)


Chemistry studies

Proust’s largest accomplishment into the realm of science was disproving Berthollet with the law of definite proportions, which is sometimes also known as Proust's Law. Proust studied copper carbonate, the two tin oxides,and the two iron sulfides to prove this law. He did this by making artificial copper carbonate and comparing it to natural copper carbonate. With this he showed that each had the same proportion of weights between the three elements involved (Cu, C, O). Between the two types of the other compounds, Proust showed that no intermediate indeterminate compounds exist between them. Proust published this paper in 1794, but the law was not accepted until 1811, when the Swedish chemist Jöns Jacob Berzelius gave him credit for it.

There are, however, exceptions to the Law of Definite Proportions. An entire class of substances does not follow this rule. The compounds are called non-stoichiometric compounds, or Berthollides, after Berthollet. The ratio of the elements present in the compound can fluctuate within certain limits, such as in the example of Ferrous oxide. The ideal formula is FeO, but due to crystallographic vacancies it is reduced to about Fe0.95O


Proust was also interested in studying the sugars that are present in sweet vegetables and fruits. In 1799, Proust demonstrated, to his class in Madrid, how the sugar in grapes is identical to that found in honey. This later became known as glucose. Overall, Proust discovered three types of sugar during his studies.


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