The Law of Define Proportions

“The elements in a chemical compound are always present in the same propotions by mass” This is also known as mass % or % composition

Discovered §

Late 1700s Joseph Louis Proust analyzed a sample of CuCO and found that all the samples he tested contained the some propotion (Composition) of copper, carbon, and oxygen. This led to the discovery of The Law of Definite Propotions