1799, The Law of Definite Proportions

Year: 1799
Chemist: Joseph Proust
Contribution: The Law of Definite Proportions

Photo Credit: daviddarling.info
By means of a series of experiments, the French chemist Joseph Proust created his Law of Definite Proportions. This law states that when compounds are broken down the elements within are always in specific proportion by mass. Stoichiometry, or chemistry math, is based off of this law.

Because of stoichiometry, John Dalton later developed his own atomic theory.

Information Credits: Royal Society of Chemistry, University of North Carolina at Chapel Hill