The beginning of the systematization of physical chemistry

At the beginning of January (including January 2), the first editions and proofs of works by Wilhelm Ostwald and Svante Arrhenius were published and distributed, dedicated to:
 • electrolytic dissociation,
 • chemical kinetics,
 • catalytic processes.

This is not a “eureka!”, but a moment when chemistry became an exact science, and not a set of recipes.