Main Page | See live article | Alphabetical index Joseph Louis Proust, born September 26, 1754 in Angers in the Maine-et-Loire, departement of France - died July 5, 1826, was a chemist. He first published his law of definite proportions (or Law of Constant Composition) in 1794. This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License.