Bibliography

Peter Pringsheim. Fluoreszenz und Phosphoreszenz im Lichte der neueren Atomtheorie. Berlin, Verlag von Julius Springer, 1921, pp. VIII + 202.

The study of the phenomena of fluorescence and phosphorescence has been going on for more than 350 years. During this time an enormous, complex, and variegated body of factual material has accumulated, urgently requiring theoretical treatment or, at the very least, rational systematization. The only objective and detailed survey of fluorescence and phosphorescence appeared in 1908 in Kayser’s Handbuch der Spectroscopie. That survey is a conscientious, detailed exposition of the raw material, without any claim to broad theoretical illumination or system. The survey ends with an abstract of Einstein’s 1905 paper, in which he attempts, by means of the hypothesis of light quanta, to explain Stokes’ law. The author of the survey treats Einstein’s attempt with complete skepticism. Since 1908 the experimental material has grown enormously, especially in the field of the study of the fluorescence of vapors. The appearance of a new survey must therefore be regarded as more than timely. From the very first pages, the author of the new book adopts the standpoint of quantum theory, which is skeptically rejected on the last pages of the old survey. According to Pringsheim’s plan, the book is to present chiefly those results that have proved essential for the construction of theory; the rest of the purely descriptive material, or material that does not fit the general point of view, the author considers it possible (in the preface) to disregard. The author’s general point of view—the Bohr theory—is, however, in its dogmatic form applicable to so small a class of facts (resonance radiation) that the author in fact, volens nolens, is led back onto the old path of a rather arbitrary exposition of complex raw material. In contrast to Kayser’s Handbuch, Pringsheim’s book is considerably less objective; the exposition in many cases is too compressed, to the detriment of clarity. Having read the book to the end, the reader will have to note with regret that, even in Bohr’s theory, the region of fluorescence and phosphorescence is still a terra incognita, in which even schematic, orienting geographical maps are lacking. Between

title and preface of the book, on the one hand, and its content, on the other—such a significant contradiction that one gets the impression that the title and preface were written earlier than the book itself. The book itself ends with a melancholy remark, with which one must agree, that “up to now there are only bricks, and for the erection of a completed structure practically nothing has yet been done.”

The content of Pringsheim’s book is, in general outline, as follows: 1. Resonance radiation and resonance spectra. 2. Band fluorescence (Bandenfluoreszenz) of vapors and gases. 3. Duration of fluorescence light and polarization. 4. Fluorescence and phosphorescence of solids and liquid solutions. 5. Phosphorescence of alkaline-earth phosphors. 6. Linear fluorescence of crystals. 7. Fluorescence of organic compounds.

Despite the undoubted failure of the theoretically coherent exposition, the specialist will be grateful to the author for his survey of extensive material, often almost inaccessible in the originals. We note with pleasure a number of valuable critical remarks by the author, for example concerning Stern and Volmer’s calculation of the duration of iodine fluorescence, the photoelectric theory of fluorescence, etc. Unfortunately, at times in the heat of polemic the author does not set out the very views he criticizes in sufficient detail (e.g., Perrin’s theory). Pringsheim evidently deliberately avoids the mathematical formulation of the theories presented, as a result of which the exposition becomes considerably vague and indefinite. Bohr’s theory and Lenard’s theory of band spectra do not require a complicated mathematical apparatus, and a concise mathematical presentation of them would have made the book more self-contained. The interpretation of Lenard’s and Stark’s theory as analogues of Bohr’s theory is perhaps admissible, but in that case one should have mentioned Wiedemann-Schmidt’s theory of fluorescence and phosphorescence, which appeared considerably earlier than Lenard’s work and was formulated in a very general form, suitable for the most diverse groups of phenomena.

Among the author’s individual misprints we note that at a concentration of \(10^{-11}\,\frac{gr}{cm^3}\) of fluorescein, in a cubic centimeter of solution there are not several thousand, but tens of millions of dye molecules.

Appended to the book is an index of works on photoluminescence that appeared from 1908 to 1921. The list contains 266 titles. The list is fairly complete. There are, however, omissions. We noticed the absence of a reference to the interesting work of Königsberger and Köpferrer on the absorption and fluorescence of dye vapors (1912), and to the books Nichols and Merritt. Studies in luminescence (1912) and E. Nichols and Nowes. Fluorescencs of uranyl salts (1919).

S. Vavilov.