Proust, Joseph Louis, << proost, zhoh ZEHF lwee >> (1754-1826), was a French chemist. He became known for helping prove the idea that every pure chemical compound consists of elements in a definite proportion. Today, scientists accept this idea as the law of constant proportions. In Proust’s day, chemists disagreed on whether the proportion of elements in a compound was definite. Claude L. Berthollet, an influential French chemist, debated Proust for years on the subject in the early 1800’s. Chemists accepted Proust’s evidence as correct by about 1808.
Proust was born on Sept. 26, 1754, in Angers, France. When in his 30’s, he moved to Spain. There, he taught chemistry in several universities and experimented in many areas of chemistry. He developed ways of obtaining sugar from grapes and did other research on foods. He died on July 5, 1826.
