Which parts of Claude-Louis Berthollet’s theory did later chemistry support?

While Claude-Louis Berthollet’s views on definite proportions were famously challenged by Joseph-Louis Proust, modern chemistry has validated several of his core insights regarding the nature of chemical reactions.

Berthollet’s most significant contribution, which later chemistry fully supported, was the realization that chemical affinities are not absolute values but are modified by physical conditions, particularly the concentration of reagents. This fundamental insight directly paved the way for the mid-19th-century formulation of the law of mass action.1

Furthermore, Berthollet’s assertion that chemical reactions seek a static equilibrium was a pioneering concept in the development of physical chemistry. Although his specific claim that all compounds could combine in variable proportions was largely superseded by the atomic theory, his broader focus on the role of mass, cohesion, and elasticity in determining the outcome of reactions is now recognized as a sophisticated and successful approach to understanding chemical behavior.12