F. N. KHARADZHA, X-ray Technology (X-ray tubes, X-ray apparatus, and the fundamentals of the application of X-rays), approved by the Main Directorate of Educational Institutions of the People’s Commissariat of the Defense Industry of the USSR as a textbook for technical schools. People’s Commissariat of the Defense Industry of the USSR—State Publishing House of the Defense Industry, Moscow—Leningrad, 1938. Editor V. V. Rzhavinsky, 202 pp.

Kharadzha’s book is the first manual on X-ray technology in the Russian language. It consists of five chapters of varying length. The first (10–30) and second (30–58) chapters, which are introductory in character, contain an exposition of the basic information from physics and the beginnings of the physics of X-rays. The third chapter (58–131), which is the central part of the book, is devoted to a description of the construction of X-ray tubes. Chapter four (131–162) contains a description of X-ray apparatus and, very briefly, X-ray installations, and finally the fifth chapter (162–190) sets forth the application of X-rays. Pp. 190–202 contain a bibliography and tables.

In its appearance the book is very well produced. The good binding, drawings, and illustrations make a pleasant impression. Unfortunately, the same cannot be said of the contents of the book. It contains a number of careless formulations and errors, many of which are of a serious character. We shall cite a few of the most significant:

On p. 13 the author writes: “... between atoms of positive and negative electricity there is a great difference. Positive electricity cannot be separated from ponderable matter and occurs in the form of ions of atoms or molecules.” What does this mean? Does it mean, in the author’s opinion, that negative electricity can be separated from ponderable matter? If so, this is an obvious absurdity both from the physical and from the philosophical point of view. And how otherwise are the quoted words to be explained? On p. 15 the author, in setting forth the theory of electrical conductivity, first confuses the theories of Drude and Thomson, which differ sharply from one another, and second, instead of them sets forth Lorentz’s theory of electrical conductivity.

On p. 18, in presenting the photoelectric effect, the author formulates the first law of this phenomenon as follows: “(1) the smaller the wavelength \(\lambda\), or the greater the frequency \(\nu\) \(\left(\lambda=\frac{c}{\nu}\right.\), where \(c\) is the speed of light) of the incident rays, the more intense (!) the photoelectric effect” (italics ours).

Further, on p. 20, in presenting secondary emission, the author writes: “(2) the maximum ratio of the number of secondary electrons to the number of primary ones lies between 1 and 1.5 for well-degassed ordinary metals and may reach values of 3–4 for metals that have not undergone special treatment; for electropositive metals this ratio is greater (up to 10).” As is known, this is incorrect.

On p. 22, in presenting the theory of the structure of the atom, the author states that the atomic nucleus is made up of electrons and protons. This error is not accidental, since still earlier (pp. 12–13), when enumerating the elementary particles, the author omits neutrons and positrons, mentioning them vaguely in a note.

From p. 30, the author begins his exposition of the physics of X-rays. Here too, however, matters go no better. Already on p. 31 we encounter the following statement: “Laue had the idea that ordinary mirrors cannot reflect X-rays because the wavelengths of these rays are very small; they are enormous compared with the sizes of the atom. Therefore any mirror, however carefully polished, will nevertheless not be smooth for rays of such short wavelength and will only scatter them, just as frosted glass scatters light rays. It is therefore necessary to find a mirror that would be created by nature as perfectly smooth, i.e., so that no atoms protrude above one another on its surface, but would be arranged in perfectly regular rows strictly in one plane. The surface of a crystal, for example rock salt, can serve as such a mirror.” One can only be astonished here. Is the author unaware that reflection from a crystal occurs as a result of interference, and that the smoothness of the surface has nothing to do with it? Has the author really never tried to reflect a beam of X-rays from a crystal, and not noticed that even very poor crystals give reflection? This error is the most serious one for a course in X-ray technology.

On p. 35 the author writes: “From Figure 1 it is seen that each sodium atom occupies a volume \(d^3\) and each chlorine atom the same volume \(d^3\); consequently, the molecule of salt occupies a volume \(2d^3\).” This is completely incorrect. First, NaCl is built not of atoms but of ions, and the sizes of the sodium ions (1 Å) and chlorine ions (1.8 Å) are not the same. As for the quantity \(2d^3\), it follows from the simple consideration that each elementary cell contains \(\tfrac{1}{2}\) of a sodium ion and \(\tfrac{1}{2}\) of a chlorine ion; consequently, the molecule is contained in two elementary cells.

On p. 36, Fig. 13 (a spectrogram) is given. What is depicted in it is known, probably, only to the author, but in any case it has nothing in common with an X-ray spectrogram.

In describing the tube with a rotating anode (pp. 124–126), the author uses a formula for calculating the dependence of the possible load on the speed of rotation. Meanwhile, the formula he gives is incorrect, since it does not take into account that, with a large increase in speed, time is needed for the anode to cool; thus there can be no direct proportionality between the number of revolutions and the power. Moreover, as direct experimental work has shown, this formula, in the form in which the author applies it, gives extremely understated values for the powers, which has also been proved by the success of French designers.

On p. 179 it is written: “In every crystal lattice one may consider an infinite multitude of various parallel, equally spaced planes, called possible faces of a cry-”

...of steel or flat lattice grids.” Here a gross error is made, since by no means every lattice can be a possible face.

On p. 184 it is stated that spots belonging to one zone will lie on one circle on the photographic plate. This, however, is also incorrect, since they will lie on one ellipse. On p. 185 the same error is repeated.

We shall not list all the other, more minor errors made by the author; we shall point out, however, that they are chiefly concentrated in the first, second, and last chapters, which are written quite illiterately.

The main part of the book, i.e. the description of the construction of X-ray tubes, does not contain such obvious errors, but it cannot be called successful either. The book makes almost no mention of the designs of modern powerful demountable tubes, which are acquiring ever greater importance with each passing day. High-voltage tubes are not described and are not even mentioned. Yet in recent years their importance has increased enormously. Questions of entirely metallic tubes are covered in a quite outdated way. In general, the entire exposition in this part is rather badly out of date in comparison with the present state of technology and corresponds, at best, to the level of 1930–1931.

On the whole, it is perplexing how the author could have written such a book, how the editor could have failed to correct its errors, how the publishing house could have issued it, and how the Main Administration of Educational Institutions could have approved it as a textbook for technical colleges. In our opinion, this last decision requires urgent reconsideration.

D. Gogoberidze, Leningrad