P. P. Lazarev, Fundamentals of the Theory of the Chemical Action of Light. Part One. General Photochemistry. Pg. 1919. Pp. 60 + IV. Part Two. Special Photochemistry. Pg. 1920. Pp. 70 + II. Part Three. Appendices to Photochemistry. Pg. 1920. P. 64.

The first beginnings of photochemical research go back as far as the 18th century; however, despite the full importance of certain old works on photochemistry (for example, the classic investigations of Bunsen and Roscoe), these works represent only a fortunate, highly promising

episode, but did not form a new scientific discipline. Yet it seemed that, just as up to the present time such stages have appeared along the path of progress of human technology as the “age of steam,” the “age of electricity,” so, with the further onward movement of humanity, it will have to enter the “era of photochemistry.” The considerations here are very simple. The energy, depending on the reserves of hard coal in the earth’s crust, will suffice for mankind for approximately only a thousand years; meanwhile the earth receives from the sun such a quantity of radiant energy which, when expressed in technical units, leads to the figure of more than \(2 \times 10^{14}\) horsepower; this is a million times greater than all the mechanical power that is now consumed by mankind. In the present geological epoch the plant world utilizes about three millionths of the share of that energy which is sent to our planet by the sun; the rest is dissipated without doing useful work. It is clear that if mankind does not wish to return to primitive culture, it will have, one way or another, to learn to use the radiant energy of the sun; and this, apparently, will be practically feasible only through photochemical processes.

But besides the capital technical problems which photochemistry must solve in the future, we may expect from it answers also to other inquiries—of a more abstract order, but no less important in their way.

The most subtle, the richest in variety of impressions, the most precious sense for man—the sense of sight—is founded on photochemical processes. This makes photochemistry a branch of knowledge that must occupy a prominent place among the sciences corresponding to the principle \(\Gamma\nuῶθι\ σεαυτόν\).

This is not all. As has become clear at the present time, the photochemical process is reduced to a successive transformation of three of the most mysterious forms of energy: radiant, electrical, and chemical. And this same process contains within itself the most fundamental transformations to which matter can be subjected. Hence it follows that from photochemical investigations one may expect, if not a final answer, then in any case a considerable clarification of such questions as: “what is energy?”, “what is matter?”, “what is electricity?”

It may be said that as a scientific discipline, defined by its chief methods and having clearly outlined its desirable achievements in the sphere of pure theory and in the sphere of practical applications, photochemistry has existed only since the twentieth century.

P. P. Lazarev had the honor of being one of the pioneers of photochemistry as a science—having labored especially much, and especially systematically, for it both on the basis of experiment and in the theoretical

correction. Almost at the very beginning of his scientific activity he had occasion to play an important role in establishing the basic photochemical law; through his investigations phenomena were clarified and brought under accounting which, being at the very heart of the matter complicated cases of the application of this law, might at first glance have seemed deviations from it; he indicated a simple and clear molecular-electronic theory of photochemical actions; he provided a logical and simple classification of photochemical reactions; through the experimental work of himself and his collaborators (Vavilov, Kravkov, Laubert, Predvoditelev, Selyakov, Shvedov, Shpolsky, Shodro) a number of important special problems were solved; finally, to him belongs the outstanding merit of applying photochemical concepts and the equations of photochemical kinetics to the processes of vision.

The full value is clear which the exposition of a scientific discipline by a person who, by his own labors, has taken such a great part in its creation must have. And although The Foundations of the Doctrine of the Chemical Action of Light is, unfortunately, not a textbook but only a survey (at times even somewhat too condensed), and although the exposition of the book bears the imprint of a certain haste in the work1—nevertheless we are convinced that, even in their present form, the Foundations will play an enormous role in disseminating correct information about the significance of photochemistry and in attracting new adherents to it and guiding them.

Since at present, unfortunately, the book is, generally speaking, a little-accessible object, the reader who might wish to become acquainted with the Foundations even only externally will scarcely find it easy to realize his wish. We therefore consider it necessary to list at least the principal sections into which the work is divided. In the first part (“General Photochemistry”), after a historical survey, there is a brief account of the photoelectric effect and its theories, and in connection with this also of the theories of the photochemical process. The end of the first part is devoted to the equations of the kinetics of photochemical reactions for the most general cases. In the second part (“Special Photochemistry”) the methodology of the photochemical experiment and the instruments used here are described; then follows a description of separate classes of photochemical reactions in gaseous, liquid, and solid media, and in conclusion a classification of reactions is established. The contents of the third part (“Applications of Photochemistry”) consist of photochemical processes in plants, in the simplest organisms, in the retina of the eye, and in the photographic plate.

In conclusion we wish that the author may as soon as possible obtain the opportunity—

…opportunity to publish his book in one of the languages of Western Europe, where the readers of this book will number not in the hundreds, as among us, but in the thousands, and where its influence will be able to manifest itself in full measure.

A. Bachinsky.

1. In particular, a defect is the absence of an index of subjects and names. ↩