Why did laboratory reactions between limestone and seawater challenge Claude-Louis Berthollet’s ideas about chemical affinity?

Claude-Louis Berthollet’s observations of the natural formation of natron (hydrated sodium carbonate) from limestone and seawater in a valley near Cairo challenged his understanding of chemical reactions because the result differed from laboratory experiments using the same components.1

While the natural environment produced natron, laboratory reactions yielded an inverse product. This discrepancy led Berthollet to conclude that chemical affinities did not possess absolute values, as was the prevailing view at the time. Instead, he proposed that the outcome of a reaction is significantly modified by physical conditions, particularly the concentration of the reagents.1

This insight suggested that chemical reactions seek a static equilibrium influenced by mass and other physical factors, a concept that eventually contributed to the formulation of the law of mass action. His challenge to the existing theories of elective affinities sparked a notable debate with Joseph-Louis Proust regarding whether compounds always combine in definite proportions.12