FROM THE HISTORY OF PHYSICS

ON THE 150th ANNIVERSARY OF THE PUBLICATION OF V. V. PETROV’S BOOK “NEWS OF GALVANI-VOLTAIC EXPERIMENTS”

N. A. Kaptsov

One of the remarkable events in the history of Russian science was the appearance, one hundred and fifty years ago, of the book by the outstanding Russian experimental physicist Vasilii Vladimirovich Petrov: “News of Galvani-Voltaic Experiments, which were performed by Professor of Physics Vasilii Petrov by means of an enormous pile battery, sometimes consisting of 4200 copper and zinc disks, and located at the St. Petersburg Medical-Surgical Academy,” printed “in St. Petersburg, at the printing house of the State Medical Collegium, in the year 1803.”

In 1800 a letter was published by the Italian physicist Volta, in which he described the galvanic battery he had built for the first time—the so-called voltaic pile. V. V. Petrov was among the first to construct, after this report, a voltaic pile in his laboratory, at first from 200 disks. Then, in 1802, he built that “enormous” battery which is mentioned in the title of his book. As M. A. Shatelen rightly notes,* it was the most powerful battery of galvanic elements “of all those then existing in the whole world.” With this battery V. V. Petrov carried out in the laboratory of the Medical-Surgical Academy in Petersburg a number of remarkable experiments on the passage of electric current through various bodies, including air at reduced pressure, and discovered many new phenomena previously unknown. The description of these phenomena constitutes the content of Petrov’s book. It gives a detailed account of the manufacture of the enormous battery and of the care required for it. Already

* M. A. Shatelen, Russian Electrical Engineers, Gosenergoizdat, 1949, p. 47.

in this description. Petrov reveals himself as a skillful experimenter, carefully thinking through all the details of his apparatus and guided by definite theoretical ideas about the essence of the phenomena he was investigating. Petrov’s ideas about the electric current were closely connected with his views in the field of chemistry, in which he was an ardent opponent of the phlogiston theory. He regarded the electric current as the flow of a “galvani-voltaic fluid,” and attributed the phenomena accompanying the electric current to the action of an “oxygenous substance.”

In the title of the third chapter of the book he mentions “the galvani-voltaic fluid” alongside “metals and certain other bodies.” He explains the oxidation of the zinc and copper disks of the voltaic pile, and the need to combat this oxidation by carefully cleaning them, by the presence of oxygen in this fluid as he supposed. Petrov begins his experiments with the decomposition of liquid bodies by the galvanic current, making at the same time many incidental observations, remarkable for that period, when nothing was yet known of the law later discovered by Ohm, and the concept of the electrical resistance of bodies was very vague. Thus, he comes to the conclusion that ice is a poor conductor of current, while wax and sealing wax are insulators; in liquids he establishes the appearance and motion of gas bubbles at the electrodes and the change in the color of chemical indicators when a current passes through a liquid. He describes the action of current on living bodies and the change in the composition of the air in a room during the operation of a voltaic pile.

Petrov observes the oscillations of a light cork ball suspended on a thin thread in the space between two metallic electrodes connected to the poles of his “enormous battery.” Petrov understood the results of this experiment, pointing to the alternation of attraction and repulsion of the ball at each of the electrodes. In doing so he proposed a quantitative method for determining the “force of action” (i.e., in essence, the voltage) of batteries by the smallest distance between the electrodes at which continuous oscillation of the ball from one of them to the other still occurred. But the most remarkable thing was the discovery by V. V. Petrov of the electric arc. After he had found “luminous phenomena” when carbon electrodes connected to the poles of a battery were brought together in oil, he decided to test what would happen if the same bringing together were performed in air. Petrov describes the result obtained in the seventh chapter of the book in the following words: “If two or three pieces of wood charcoal are placed on a glass plate, or on a little bench with glass legs ... and if, by means of metallic insulated guides ... connected with both poles of an enormous battery, they are brought nearer to one another to a distance of from one to three lines, then there appears between them a very bright white-colored light or flame, from which those pieces of charcoal ignite sooner or more slowly and from which the dark

Report on Galvani-Voltaic Experiments

which were conducted by

Professor of Physics Vasily Petrov,

by means of an enormous battery, consisting at times of 4,200 copper and zinc disks, and located at the St. Petersburg Medico-Surgical Academy.

In St. Petersburg,

In the Printing House of the State Medical College, 1803.

such a current may be quite clearly illuminated.” V. V. Petrov did not limit himself to this discovery. Adhering to the main direction of his scientific work, he began to study how various bodies behaved, or how they “burned,” in the electric arc, either used as electrodes or introduced directly into the “flame” of the arc. “Finally,” he writes, “by means of the fire accompanying the flow of the galvanic-voltaic fluid, when using an enormous battery, I attempted to transform red lead and mercuric, as well as gray tin, oxides into the metallic state; the results of the same experiments were such that the aforementioned oxides, mixed with powdered charcoal, tallow, and expressed oils*), upon the combustion of these combustible bodies, sometimes assumed the true metallic appearance with a flame.” Thus, in the News of Galvanic-Voltaic Experiments we find the first indication of the possibility of applying the electric arc in metallurgy. In the description quoted above of the discovery of the electric arc there is also a clear indication of the possibility of using it as a source of light. In the last chapter of the book Petrov describes experiments in which he placed electrodes made of various bodies, connected with the poles of his batteries, in rarefied air under a glass bell jar connected to an air pump. The purpose of these experiments was to investigate the course of chemical reactions taking place under the action of an electric current (or, in his terminology, the “combustion of complex solid combustible bodies by means of the galvanic-voltaic fluid in an airless place”). The lowest air pressure that he was able to achieve in these experiments was 6 mm Hg. From Petrov’s description of these experiments it is evident that he observed various forms of gas discharge, ranging from a glow discharge at low pressures to a spark discharge at high ones. Thus, it may be asserted that Petrov’s book describes the first systematic experiments on electrical discharges in air at various pressures.

Despite certain statements encountered in the literature that the discoveries of V. V. Petrov found a response in Russia and were known to some scientists abroad, his works and the three books written by him describing these experiments were forgotten after his death. To a considerable extent this was the fault of such official representatives of science as Academician Kraft, who in his articles on the electric arc did not even mention the name of V. V. Petrov. As a result, it came as a complete surprise to the physicists of Petersburg—where Petrov lived, worked, wrote, and published his books—when in 1887 A. L. Gershun, later a well-known professor of physics, and then still a student of Petersburg University, accidentally found in the public library of the city of Vilna a book

*) That is, vegetable oils obtained by pressing fruits, seeds, and other parts of plants.

Petrov’s News of Galvani-Voltaic Experiments. Only after this was the attention of Petersburg scholarly circles drawn to this book; two other books by Petrov were also discovered: the Collection of New Physico-Chemical Experiments and Observations by Vasilii Petrov, Professor of Physics at the Saint Petersburg Academies of Medicine and Surgery and of the Free Arts, published in 1801, and the New Electrical Experiments of Vasilii Petrov, Professor of Physics, by which he proves that insulated metals and people, as well as many merely heated bodies, can be made electrical by friction—especially by rubbing them with furs beaten to a deliberate softness—and by certain other bodies; likewise special experiments, made in various ways, to discover the cause of electrical phenomena, published in 1804. Thus, only 85 years after V. V. Petrov’s discovery of the electric arc was his priority in this discovery restored.

Nevertheless, Petrov’s work was carried on—without their themselves knowing it—by other Russian scientists of the nineteenth century. Pavel Nikolaevich Yablochkov used Petrov’s arc to create the first practical scheme of electric lighting, which became widely disseminated in Europe in 1876–1879 under the name “Russian light,” “Northern light” (La Lumière Russe; La Lumière du Nord). Vladimir Nikolaevich Chikolev was the creator of “arc lamps” with differential regulators and, together with A. N. Lachinov, carried out an extensive study of the electric arc. The mining engineer N. G. Slavyanov and N. N. Benardos, independently of one another, proposed and developed in the early eighties methods of welding metals, which at that time found broad application both in Russia and abroad and laid the foundation for the modern technology of electric welding, now being vigorously and fruitfully developed by the work of Soviet scientists.

Finally, in 1905 V. F. Mitkevich—then still a young physicist and later an academician—established the nature of the processes taking place at the cathode of Petrov’s arc. The electric arc, first produced in 1802 by V. V. Petrov, had a small current and low power. At present, in technology, electric arcs with currents on the order of tens of thousands of amperes are used in so-called arc furnaces.

These grand achievements were brought about by the discovery of the electric arc, modestly described by V. V. Petrov in the book News of Galvani-Voltaic Experiments. But only in our time has Petrov’s wish, expressed by him in the same book in the words, been fulfilled: “I hope that enlightened and impartial physicists will someday agree to give my labors that justice which the importance of these latter experiments deserves.”