Bibliography

N. Seménoff. Chemical Kinetics and Chain Reactions, 480 pp., Oxford Press, 1935, Sh. 35.

N. Semenov. Chemical Kinetics and Chain Reactions, Leningrad, ONTI, Khimteoret, 1934.

The reviewer of this book had the good fortune to experience directly the evolution of chemical kinetics under the influence of chain theory, whose development began in 1913, when the reviewer, as a junior collaborator, worked in Bodenstein’s laboratory. Later the universality of the phenomenon of chain reactions was noted more than once; for example, in considering technical questions connected with slowing the course of decomposition reactions, questions of the combustion of petroleum fuels, and also in the theoretical consideration of thermal and photochemical decomposition, polymerization, and synthesis, one always felt the need for an exhaustive presentation of the problem as a whole. And yet one is struck by the breadth with which the problem is encompassed in the masterly exposition of the Leningrad professor Semenov in the present book. Semenov approaches the problem from the standpoint of oxidative processes leading to ignition and explosion, and to him we owe the vigorous development of the theoretical formulation of these processes. Into other areas of the problem of chain reactions the author has brought his characteristic freshness of view and, in this way, gives the reader an exhaustive, unified exposition of the entire subject.

In the first part of the book, on 80 pages with a few additional pages, the foundations of chain theory are set out in detail and skillfully: the theory of unbranched and branching chains, as well as of “degenerate” branching. Here only one remark might be made, namely that up to the present time, insofar as the composition of the walls, the dependence on temperature conditions, and the physical state of the surface are concerned, the extremely interesting influence of the wall on the reaction rate can be considered only from the qualitative side. The influence of the walls plays an especially important role in the case of chains with “degenerate” branching. Too often the investigator has been interested exclusively in tracing the path of the active center from the moment of its origin to the moment of reaction at the wall, where interest in the phenomenon immediately disappeared.

In the most recent literature there are indications that the fate of organic radicals, such as methyl, at the moment they reach the surface is determined to a considerable degree by the temperature conditions and also by the composition of the surface. These influences will have to be taken into account when comparing photochemical data at low temperatures with thermal data in the region of higher temperatures.

Chain reactions of halides with hydrogen, carbon monoxide, and also with hydrocarbons and other organic compounds are described in the second part, on the next 80 pages. The chapters devoted to hydrogen and carbon monoxide have been originally recast in comparison with earlier treatments of the same subject. The chlorination of hydrocarbons is described briefly, with an indication of the need for additional data, especially with respect to thermal reactions.

In the third part, oxidation processes are considered from the point of view of chain theory. For foreign countries this part is the most valuable, since in it, in an exhaustive manner, data have been collected,

obtained in the USSR by Semenov and his numerous collaborators, which until now have been little accessible to foreigners; there is hardly anywhere such a skillful comparison of these data with results obtained in other research centers. In addition to gaseous systems, the chain mechanism of oxidation of liquid systems, such as benzaldehyde and sodium sulfite, is also considered.

The last 90 pages of the fourth part are devoted to decomposition processes, both thermal and photochemical, in the gaseous, liquid, and solid phases, to polymerization processes, and to the anomalous characteristics of certain monomolecular processes. On the last two questions rapid successes are at present being observed, and there are indications of a wide diffusion of chain characteristics exceeding all expectations. Later, in moving on to chain reactions, the consideration of the polymerization of ethylene should be added. Some time ago it became known that the presence of small amounts of oxygen and of free radicals leads to thermal polymerization. The amount of data is steadily increasing indicating that the decomposition of hydrocarbons, which has always been regarded as a monomolecular reaction, is induced by radicals or by parts of complex compounds that readily dissociate on heating. It is not difficult to take into account the entire technical significance of these results.

This book will be of benefit to anyone studying the kinetics of chemical reactions. The book represents a major contribution of Soviet science to modern physical chemistry. It is indispensable for anyone who would wish to begin work in this field. It is excellently composed, easy to read (although the complexity of the mathematical symbols required makes the reading of the first part comparatively difficult), and beautifully printed and published. The reviewer found no more than ten insignificant misprints. One cannot but admire the uniformity of the exposition as a whole, especially since such uniformity is greatly hindered by the rapid development of this field.

The book under consideration by no means closes an epoch in the kinetics of chemical reactions, as may be seen from its final, hundredth, paragraph. Here Semenov sketches the outlines of that difficult task which lies ahead: “This new field of human knowledge—the study of matter during transformation, the study of macroscopic processes occurring in chemical bodies”*.

We shall have to deal with the varying ability of individual forms of energy to undergo transformations, beginning with the particular case of excitation energy and ending with vibrational, rotational, and translational energies of the system. It is not necessary that the distribution of energy according to the Maxwell–Boltzmann law should predominate. In the reviewer’s opinion, the outstanding works carried out in recent years by Eyring, proceeding from Geytler–London ideas on potential surface energy and finding their completion in Eyring’s recent theory of the activated complex and its statistical interpretation, are the first approach to solving this more difficult problem of the kinetics of chemical reactions, which Semenov formulated so well in the concluding words of the book:

“During the coming decade theoretical chemistry must concern itself mainly with the study of chemical transformations based on the statistics of stationary processes, and also with a detailed analysis of elementary acts of energy transfer and with the study of the nature of the atoms and unstable molecules which form part of the intermediate products of chemical reactions.”

For those who would venture to set out for this promised land, the present book on chemical kinetics and chain reactions will prove an invaluable preparatory course.

Yu. S. Taylor, Princeton, USA*

* Translated from the manuscript.