Perrin’s Experiment Handed Ostwald 'Avogadro’s Constant': He Lauded the Results but Did Not Move to Associate the Number with the Mole Definition

Wilhelm Ostwald was a notable holdout against the acceptance of the reality of atoms. He steadfastly maintained a positivist perspective, that the empirical facts of chemistry implied no underlying meaning about the nature of matter. The amount of substance definition of the mole aligned with this view. He was moved to accept the reality of atoms based on the results of experimental work on Brownian motion by Jean Perrin, that gave a name to, and a value for, Avogadro’s constant. Ostwald could have modified the definition of the mole, making use of the constant to incorporate the atomic nature of matter into the concept. If he had, difficulties with the definition that persist today might have been avoided.