Dreams and Visions in a Century of Chemistry

In addition to accidental observations, analogies, and inferences by close reasoning, dreams and visions had an important part in the progress of chemistry. Four classes of progress can be distinguished: (1) symbolization and construction of models: Kekulé, van't Hoff, J. J. Thompson; (2) extrapolation in quantity: Wöhler, Sabatier, Kurnakow; (3) projection in time: Kuhlmann, Le Bon, Aston; (4) generalizations: Clausius, Le Chatelier, Ostwald. This list is incomplete and leaves out the failures. Not all those with dreams and visions were as careful as Kekulé was to check and test before publishing. The courage to persist must be combined with a critical evaluation of the facts, and this is especially necessary when solutions are achieved primarily in broad jumps rather than small steps.