Joseph Proust

Joseph-Louis Proust was born on 26 September 1754 in Angers, France. His father served as an apothecary in Angers. Joseph studied chemistry in his father's shop and later went to Paris where he gained the appointment of apothecary in chief to the Salpêtrière. He also taught chemistry with Pilâtre de Rozier, a famous aeronaut. Under Carlos IV's influence Proust went to Spain. There he taught at the Chemistry School in Segovia and at the University of Salamanca. But when Napoleon invaded Spain, they burned Proust's laboratory and forced him back to France. On 5 July 1826 he died in Angers, France. The mineral proustite (Ag3AsS3) is named in his honour. ==Chemistry studies==

Proust's largest accomplishment in the realm of science was disproving Berthollet Between the two types of the other compounds, Proust showed that no intermediate compounds exist between them. Proust published this paper in 1797, but the law was not accepted until 1812, 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 for example 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. ==Works==

• Joseph Louis Proust (1794 [i.e., 1797]) "Recherches sur le Bleu de Prusse" (https://gallica.bnf.fr/ark:/12148/bpt6k9604748r/f348.image) [Researches on Prussian blue] ''Journal de Physique, de Chimie, et d'Histoire Naturelle'' 45 334–341. This work was actually published in 1797, as can be seen from the article published in the same issue on page 314. • • • • • • • • • • • • • • • • Translated to German in Journal für die Chemie und Physik vol. 1 (1806) p. 249-270 • • • • • ==References==