How did John Dalton’s atomic theory affect the Berthollet-Proust debate?

The debate between Claude-Louis Berthollet and Joseph-Louis Proust centered on the nature of chemical combination. Berthollet argued that substances could combine in variable proportions, while Proust maintained that elements combined in fixed, constant proportions.12

John Dalton’s atomic theory provided the theoretical framework that eventually settled this dispute in favor of Proust. By proposing that elements are composed of discrete atoms with unique, characteristic weights, Dalton’s theory offered a logical explanation for why chemical compounds must contain elements in fixed, integral ratios.213

While Berthollet’s views on variable proportions were rooted in his observations of solutions and physical conditions, the subsequent conceptual relationship established between Proust’s law of definite proportions and Dalton’s atomic theory—further solidified by the work of Jöns Jacob Berzelius—demonstrated that chemical compounds are defined by these constant atomic ratios. This effectively marginalized Berthollet’s position, as the atomic model became the standard for understanding chemical composition.23