Catalytic and induced reactions. —Part I. Catalytic and induced oxidation in the presence of salts of cerium

Work upon the phenomena of induced oxidation dates from the researches of Schönbein (1), who showed that during the autoxidation of many substances —e. g ., turpentine and benzaldehyde—for every molecule of oxygen consumed by the primary substance undergoing oxidation, another molecule of oxygen was simultaneously transformed into a more active state; this active oxygen could then react secondarily with certain other substances—e. g ., indigo blue—effecting oxidations which could not be accomplished by ordinary atmospheric oxygen. This activation of oxygen Schönbein termed “ozonisation”; as the result of the observation that ozonised turpentine reduces lead dioxide to the monoxide, he was led to the supposition that active oxygen exists in two forms of opposite sign, which he termed ozone and antozone. He thereby adopted the conception of polarity previously introduced by Brodie (2), though the latter did not support Schönbein in his division of the peroxides of the alkalies and of the heavy metals into antozonides and ozonides respectively. R. Clausius (3) stated that ozone and antozone could be regarded as oppositely charged oxygen ions, a view adopted by van't Hoff (4), who suggested that the equilibrium O2 → ← O+ + O- already exists in atmospheric oxygen, since he had observed that when phosphorus undergoes autoxidation in the presence of indigo, a continual supply of fresh indigo was necessary in order to maintain the reaction velocity at a reasonable figure; this, he considered, supported the above hypothesis, since accumulation of ozonic oxygen (removed by excess of indigo) would diminish the active mass of the antozone oxidising the phosphorus.