From Lavoisier to Dalton:
Debating the Law of Definite Proportions

by Kelly Strandemo

Are elements composed of discrete entities, such as atoms, or is matter not constrained by such rules? In the early 1700s, after Lavoisier had profiled the elements as we now know them, debate raged on whether elements combined in definite proportions (indicating compounds of discrete entities) or in any ratio whatsoever. The key advocates, Prout and Berthollet, each had a vision of matter based on their experience and interpretation of the evidence. This module follows that debate, showing how we came to a Daltonian undertanding that matter is composed of atoms, each with a characteristic mass.

Open Word document.