J. H. DE BOER — Electron emission and adsorption phenomena. Transl. from the manuscript by H. E. Teves-Anly. L., Cambr. Univer. Press, 1935, XI, 398 p., 150 Fig. (The Cambr. ser. of physical Chemistry. Gen. ed. E. K. Rideal). Sh. 21.

J. H. de Boer — Electron emission and adsorption phenomena.

In the phenomena of photoelectric and thermionic emission, which, as is known, have found extremely broad technical application, a particularly important role is played by the so-called “compound cathodes.” In these cathodes electron emission takes place from a surface consisting of several thin layers of a metal or a metallic compound deposited on a base cathode. The phenomena observed in this case are much more complex than, for example, the photoeffect from the surface of a pure massive metal: in a compound cathode there occurs a “selective” photoeffect, important in practical terms and very interesting for theory. The value of de Boer’s book lies in the fact that the author approaches the phenomena occurring in compound cathodes both from the standpoint of electronics and from the standpoint of adsorption theory. He carefully studies the question of the structure of adsorbed thin layers, of the adsorption potential, and of the work which, for various structures of the layer, must be expended to free an electron from an atom (the ionization potential of the adsorbed atom).

As a result, de Boer becomes convinced of the necessity of distinguishing two phenomena, different from one another: photoemission of the electron conductivity of the metal and photoionization of individual atoms adsorbed on one or another “underlayer.” The consistent development of this idea and the analysis of the conditions of ionic and electronic conductivity of the semiconductor constituting the intermediate layer between the massive part of the cathode and the surface monatomic metallic layer allow the author to sketch a coherent picture of the entire process of photoemission, into which not only qualitatively but, to a considerable extent, also quantitatively, almost all the details of the observed phenomena fit well. From the same standpoint the author gives an interpretation of the processes of activation and operation of “oxide” thermionic cathodes. The experimental material on which the author bases himself was collected by him in a significant measure in the research laboratory of the Philips works at Eindhoven, where the author has been working for a number of years on compound cathodes. The book was written at the suggestion of a group of English physical chemists, made to the author precisely because he is one of the most active workers in this field. The presentation of the book is simple and clear, which makes it accessible to persons familiar with the fundamentals of electronics and the theory of adsorption. The author gives rich bibliographical material; the references extend up to the first months of 1935, and there are indications of a number of works by the author and his collaborators expected to appear in print during 1935.

As for the shortcomings of the book, the author may be reproached for a certain diffuseness of exposition and for the fact that he sometimes gives minor details which could have been replaced by references to the appropriate literature. In places the author repeats himself. Thus, when beginning a new chapter on one or another type of compound cathode, he repeats the conclusions and propositions to which the preceding chapters have led. This, on the one hand, gives independent significance to each chapter separately and facilitates its reading independently of the other chapters. If, however, the book is taken as a whole, these repetitions impair the impression in sequential reading. The author should also have indicated the sources of the numerous potential curves which he gives for various cases of adsorption of atoms and ions.

The order of exposition in the book is as follows: the first two chapters constitute a survey of the contemporary theory of electron emission and of the nature of adsorption forces. Chapters 3, 4, and 5 deal with phenomena occurring when thin layers of one metal are adsorbed on the surface of another. Chapter 6 is devoted to the adsorption of gases; in chapters 7 and 8 раз-

absorption of light by atoms of a gas and by atoms adsorbed on a surface are examined. The following chapters contain an explanation of various processes of emission in compound cathodes and of processes for replenishing the supply of emitted electrons by their passage through one or another intermediate layer. Chapter 14 examines phenomena in oxide thermocathodes and, finally, the last, Chapter 15, processes in cathodes with a locking layer.

The large amount of experimental and theoretical material collected in the book under review, treated from the author’s original point of view (to a considerable extent quite justified), makes it advisable to recommend a detailed acquaintance with it to all those working practically in the field of the photoelectric effect and oxide cathodes, as well as to all those concerned with the theory of these problems. Publication of de Boer’s book in Russian is highly desirable.

N. Kaptsov

M. T. ZARAFYANTS — What Is Entropy. State Scientific-Technical Publishing House of Ukraine, Kharkov—Kiev, 1935, p. 83, price 2 rubles, print run 4,000.

The book by M. T. Zarafyants forces one once again to raise the question of the responsibility of our scientific publishing houses for the literature they issue. This book can do much harm, since if it gives the qualified reader only a few amusing hours, it will disorient the beginning reader and create complete confusion in his head.

The purpose of the book is characterized by the preface: “There are no scientific novelties in this book.” The novelties here are methodological and pedagogical. They are partly borrowed by the author from Prof. Fater, Satkevich, and others. But his own contribution has also been made to the difficult task of popularizing entropy, one which, as experience has shown, leads to brilliant results.* Let us take a closer look at this “contribution.”

In order to give an idea of the character of the book, let us cite the “first conception of entropy.” In the author’s opinion, “the peculiarity of thermal energy in its transformation into work is best formulated as follows: in the transformation of heat into work in a real heat engine, nature levies a tax. The temperature coefficient of this seeming tax is called entropy.”

Thus, according to this “conception,” which the author calls “dynamic,” entropy is nothing other than the temperature coefficient of a tax which is, as it were, levied by nature. There is no point in giving other endings, since the author himself considers that “the first definition must be recognized as the most fruitful.”

The author again gives this completely meaningless formulation on p. 73 among the classical formulations of Clausius, Planck, and others, as equal in status to them.

In general, instead of giving a clear and vivid interpretation of the most successful classical formulations of entropy, the author has followed the path of piling up a large number of naive and confused arguments, which have completely obscured the essence of the question. Thus, for example, on p. 78 a list is given of 12 formulations of the second principle, and on p. 71, under the heading “Content of the Concept of Entropy,” 12 points are likewise given which, according to the author’s idea, are to convey the essence of this concept. Let us cite some of them, since in essence they summarize the material and very vividly characterize the style of the book:

1. Entropy is not an a priori concept, not a concept susceptible to direct perception. The only concept related to entropy is the moment of inertia of a body.

2. Entropy and the moment of inertia are concepts introduced into science by science itself. Entropy and the moment of inertia are auxiliary functions for solving practical problems.

Besides the unexpected analogy with the moment of inertia, these formulations contain a number of word combinations whose meaning is quite problematic. For example, “entropy and moment of inertia are concepts introduced into science by science itself.”