CATALYSIS AND CHEXICAL ENERGY
BY OSCAR LOEW
Recently an article appeared in Vol. 31 of the Zeitschrift fur physikalische Chemie by G. Bredig and R. Muller von Berneck, which contained a short review of the different hypotheses in regard to the phenomenon of catalysis. Thk review may be completed by the following paragraphs : I n t h e first place, the view of Ostwald’ expressed in 1895 should be (quoted : ( ( W h a t causes the action of catalytic substances is at present still a mystery, the solution of which is the more difficult, as it can only be found on the basis of new principles which reach beyond the laws of energy.” I n the second place that of the writer should be mentioned, in regard to the catalytic action of platinum black at the ordinary temperature.’ According to this view it is the oscillations of the free heat energy of the atniosphere which are modified by certain peculiarities of the platinum atom in such a manner that they can pass still more easily than they usually do into the oscillations of chemical energy. These modified oscillations become still more powerful when the platinum black has absorbed molecular oxygen to which these modified heat oscillations are transferred. T h e writer has observed that platinum black charged with oxygen can cause a reduction of nitrates to ammonia in presence of glucose, and that this process stops when the molecular oxygen surrounding the platinum particles is removed or consumed by a secondary action consisting in a direct oxidation of glucose. T h e absorbed oxy“Worauf die Wirkung katalytischer Stoffe beruht, is 1 Aula, Heft. I . zur Zeit noch ein Raethsel, dessen Loesung urn so schwieriger ist, als sie nur auf grund neuer Principien, welche iiber das Energiegesetz hinausgehen, gefunden werden konnte.” Ber. chem. Ges. Berlin, 23, 677 (1900).
6.58
Oscav Loew
gen becomes a powerful oxidizer under the influence of these oscillations. I t is still the general belief that the oxygen absorbed by the platinlim black owes its efficiency merely to its denser state. If that be correct then oxygen compressed by a pump ought to behave in the same way, which is not at all the case. T h e ca taly’tic action of certain organic compounds was traced by the writer to the chemical energy of labile atoms. Thus far the relations of chemical lability to chemical energy have attracted but very little attention. Atoms in labile position are characterized by a state of lively osdlations, different from the mere heat oscillations of the atoms in stable position. Oscillations due to chemical lability may be of wider amplitude than those of hedt, since the former can loosen affinities in a much more marked degree at the ordinary temperature than heat energy can do under the same circumstances. Since these oscillations can easily produce chemical changes in certain other compounds they must be defined as chemical energy. Chemical energy can occur associated with organic compounds in a potential and in a kinetic form. A kinetically labile compound is characterized on the one hand by the easy change to a more stable isomeric or polymeric modification or compound, and on the other by the great facility with which it enters into reaction with various other compounds, especially such as also possess labile properties and thus products result with a lesser degree of instability. Potentially labile compounds behave differently, they do not pass into isomeric or polymeric modifications and they do not easily yield various derivatives, but are inclined to sudden and far-reaching decomposition or explosion. Examples of the former class are aldehydes, ketones, amidoaldehydes, amidoketoneq ; of the latter class the diazo compounds and the nitrates of polyvalent alcohols, as nitroglycerol. This intramolecular potential chemical energy is to be clearly distinguished from the potential chemical energy of all organic compounds, illustrated by the process of combustion. Free chemical energy in a labile compound is caused by a
Catalysis ana! Chemical Eizergy
659
loose position of atoms in certain atomic groups and this loose position is the consequence of a depression of affinities on account of one atom being under the simultaneous influence of two neighboring atoms. Such labile atoms are subjected to much more violent oscillations under the influence of heat energy than are the other atoms in stable position in the same compound, and thus heat energy can easily pass into chemical energy through the agency of labile atomic groups. As the writer has pointed out repeatedly, the living matter and the enzymes furnish the most striking examples for this theorem. T h e reader may be referred to recent articles of the writer in k t Science,” December, 1899, and June, 1900 : On the Chemical Nature of Enzymes, and On the Proteids of Living Matter. Those who are more particularly interested in this line may be referred to the work of the writer: Die chemische Energie der lebenden Zellen, Chapters 5 and 11. Munich, 1899 : E. Wolff. publisher. In this treatise the chemical energy associated with aldehyde groups is treated in detail. P. S.-After this was written an article of Hans EulerI came to the writer’s notice in which the catalytic action of platinum black upon hydrogen peroxide was in part attributed to the oxygen condensed upon the metallic particles. He observed a very great difference in the intensity of action at the beginning of the reaction between the freshly reduced platinum black and that which had been exposed to air. Euler seems not aware that the writer, ten years before he did, drew the same inference’ as to the essential influence of the absorbed oxygen upon catalytic processes, even on some that are by no means simple oxidations, as the reaction between nitrates and glucose above mentioned. Division of Vegetable Physiology, U S. Dept. of Agiiczrlture, Washingtoolz, D. C., July, zpoo. Chem. Zeitung, Aug. 4, 1900. Extract from Akad.” Fcrhandl. 2, 267 (1900). Ber. chem. Ges. Berlin, 23, 677 (1900).
I‘
Ofversigt af Kgl. Vetensk.
