A. B. MLODZEYEVSKY, A Brief Textbook of Molecular Physics, GTTI, 1933, 3rd ed., 248 pp.

The book is an elementary introduction to molecular physics and, in its presentation, is quite well adapted for independent work by the student.

The exposition is concentrated in 12 chapters. The first three of them are devoted to the thermal expansion of bodies, the nature of heat, heat transfer and heat capacities of bodies, and methods of thermal measurements. Whereas in the subsequent chapters, where the viscosity of gases is discussed, the corresponding coefficients are interpreted from the point of view of kinetic theory, the coefficient of thermal conductivity receives no such interpretation. Speaking at considerable length throughout these three chapters about the thermal properties of bodies and, in particular, about the fact that the heat capacity of bodies changes with temperature, the author does not say a word about the successes achieved on this question by classical quantum theory. The fourth chapter deals with the general properties of gases. The fundamental gas laws are analyzed. Certain basic formulas of the kinetic theory of gases are derived clearly and vividly in an elementary way. Here, too, the van der Waals equation is derived and the nature of molecular forces is discussed. The concept of isotherms and adiabats is introduced. In this chapter the author’s tendency is especially clearly manifested not only to describe the whole complex of phenomena, but also to indicate their physical mechanism, the underlying basis of one process or another—something often omitted by compilers of textbooks. Thus, for example, in discussing the question of heat capacities at constant pressure and volume, the author always explains clearly why one of them must be greater than the other. Of course, it would have been natural to include in this chapter also some indications concerning the nature of the dielectric constant, especially since the author has to speak about dipole, quadrupole, etc., molecules when examining the question of the equation of state of a non-ideal gas. Meanwhile, the book contains nothing about the dielectric constant of matter.

The experimental foundations of molecular theory are discussed in the fifth chapter. The experimental verification of Maxwell’s velocity-distribution law, the diffusion of gases, and Brownian motion are described in considerable detail in this chapter. Much attention is given to questions of direct observation of small particles (microscopy, ultramicroscopy). The influence of diffraction on the examination of small particles under a microscope and the limits of the resolving power of the microscope are very clearly set forth. These matters, despite their simplicity, are usually accorded only a few brief remarks in most ordinary textbooks; here, however, even the ill-prepared reader, thanks to the skillful explanation, will be left with no uncertainties.

The sixth chapter is devoted to liquids. Surface tension, capillarity, compressibility of liquids, and other properties of liquids are described at considerable length. As in other parts of the book, an important merit of the exposition is the consideration of the physical picture of such processes as melting, evaporation, expansion of bodies when heated, viscous flow of a liquid, and so on. The phenomena of adsorption are treated by the author too briefly and superficially. Taking into account the scientific and practical significance of these phenomena, the absence of a detailed exposition of them in a textbook of molecular physics must be regarded as a substantial gap.

The seventh chapter is devoted to the transition from one state to another, to evaporation, boiling, and saturated vapor. It is well and excellently explained, with a physical interpretation, why the pressure of vapors saturating a space rises steeply with increasing temperature, more rapidly than in ordinary gases.

The foundations of thermodynamics are set forth in the eighth chapter and in a special appendix at the end of the book. Included here are the first and second principles of thermodynamics; the concept of the Carnot cycle and of reversible and irreversible processes is given; a derivation of the Clausius–Clapeyron equation is given, with some applications to questions concerning the dependence of surface tension on temperature.

and other properties of solids and mixtures. The last three chapters of the book are concerned with the diversity of the properties of matter. Much attention is devoted to the crystal lattice, to all kinds of liquid and solid solutions, to liquid crystals, and to boiling and crystallization.

Here, too, various deformations of solids are considered (bending, torsion, etc.), although in the form in which these questions are presented they constitute a chapter from a course in the theory of elasticity or strength of materials, and not in molecular physics.

Undoubtedly, some “modernization” of the material presented is also desirable. In particular, it is necessary to point out the successes in the field of the quantum theory of molecular phenomena, where there are a number of firmly established results. Undoubtedly, this would give the whole book much greater freshness. As an example of such a thoroughly modern book, in which not only questions of molecular physics but many others are touched upon, and in which the material is presented with account taken of the results of quantum mechanics, one may point to Eucken’s course Chemical Physics. Nevertheless, let us note that Prof. Mlodziyevsky’s book contains much that is valuable and may serve the physicist, chemist, and engineer as an introduction to the field of molecular phenomena.

G. V. Spivak