V. A. BORODOVSKY and L. S. KOLOVRAT-CHERVINSKY

(From the History of Early Radioactivity Research in Russia)

I. I. Yakobson

The discovery of the phenomena of radioactivity at the end of the nineteenth and the beginning of the twentieth centuries aroused great interest among Russian scientists of that time. This interest was determined by the understanding that, in the phenomena of radioactivity, as V. I. Vernadsky pointed out, “sources of atomic energy are being revealed, exceeding by millions of times all those sources that had been pictured by the human imagination.” V. I. Vernadsky drew attention to the question of identifying the reserves of radioactive substances present on the territory of our Motherland1234. On his initiative and under his leadership, extensive scientific work on radioactivity was developed, in which A. E. Fersman, V. G. Khlopin, L. N. Bogoyavlensky, and others took part567. A. E. Fersman headed the investigations of radioactive minerals and of their distribution over the territory of Russia. V. G. Khlopin and L. N. Bogoyavlensky undertook the search for a suitable method of obtaining radium salts. The study of the radioactivity of minerals was begun by I. A. Antipov (1900–1903)8. Among the first Russian investigators of radioactive substances, V. A. Borodovsky and L. S. Kolovrat-Chervinsky occupy a prominent place.

V. A. BORODOVSKY

Vasily Andreevich Borodovsky was born on 20/II 1878 into a large family that had early lost its father. In 1898 he entered the Faculty of Physics and Mathematics of Yuryev University. His student years passed in need and hardship. Nevertheless, in 1902 he brilliantly completed the Faculty of Physics and Mathematics and remained at the university to prepare for a professorship. In the autumn of 1907, after defending his master’s dissertation, Borodovsky began lecturing on a course in radioactivity. In 1908 he received a two-year foreign assignment and went to England, where he worked in Rutherford’s laboratory. This period of Borodovsky’s life likewise passed in difficult material

under such conditions. V. A. was sent 900 rubles a year, and even that irregularly. Abroad one could not live on this money otherwise than from hand to mouth. To support himself, Borodovsky was forced, “in exchange for a room” (without board), to do clerical work for a merchant (writing addresses on letters for Russian clients). Yet despite all the difficulties and privations, he worked very successfully in Rutherford’s laboratory. When the term of his assignment ended, Borodovsky was offered the opportunity to remain in England as a Privatdozent of the university. In view of V. A.’s difficult financial situation, the offer was tempting; however, Borodovsky declined it. He could not imagine scientific work outside Russia. “I shall not take root on English soil,” V. A. wrote on this occasion, “and like a leaf carried by a storm, I shall wither and perish; and I have decided to return to Russia.” It is interesting, incidentally, to note that he made the return journey to his homeland on a cargo steamer, for lack of funds.

Having returned to Russia, Borodovsky published the results of his scientific assignment in the work “The Absorption of Beta Rays”^10. This work presented a comprehensive and careful study of the absorption of \(\beta\)-rays in liquids. Before Borodovsky, almost no attention had been paid to this question. It is true that Norman Campbell, in 1909, made an attempt to determine the absorption of \(\beta\)-rays by solutions. Soaking filter paper with the salt solution under investigation, he placed the moist filters one upon another and studied the absorption by those layers of liquid that were contained in the paper. The inadequacy of such a method is obvious, because of the nonuniform evaporation of the liquid during observation and the absorption of the rays by the filters. Therefore Campbell’s experimental data cannot be considered reliable.

Borodovsky carefully thought out a method for obtaining thin liquid layers. After preliminary experiments with films of collodion and mica, he settled on a glass wedge. The liquid under investigation was introduced into a wedge-shaped gap between two glass plates arranged at a small angle to one another. The thickness of the layer was determined by the distance from the apex of the wedge. The ionization produced by the action of \(\beta\)-rays that had passed through the layer of the liquid under study was measured with an electroscope.

Many organic liquids and powdered bodies were investigated in glass cells consisting of small cylinders cut from thin-walled glass tubing and covered with cover glasses.

On the basis of extensive experimental material, V. A. Borodovsky established that the absorption of \(\beta\)-rays is an additive property of matter. In whatever state a given element may be found, it is characterized by one and the same unchanged absorp-

absorptive capacity. This quantity is affected neither by the state of aggregation nor by the allotropy of the chemical elements. Thus, for example, one gram of carbon in the form of graphite and in the form of coal has the same absorptive capacity. The isomerism of chemical compounds also does not change the magnitude of absorption. Thus, for example, the isomeric alcohols—propyl alcohol \(C_3H_7\) and isopropyl alcohol

\[ \begin{matrix} CH_3\\ CH_3 \end{matrix} > CH \cdot OH \]

have one and the same absorption. Since the absorption of \(\beta\)-rays is determined by the nature of the atom itself, then, by virtue of the law of additivity, the molecular absorption is equal to the sum of the atomic absorptions:

\[ M_a = \Sigma A_a . \]

If the composition of a compound, its molecular absorption, and the atomic absorptions of the elements composing it, except for one, are known, then it is easy to determine the atomic absorption of this latter element. The errors in determinations of atomic absorption of this kind are the smaller, the greater the percentage content of the element under consideration in the given compound.

Comparing the quantities characterizing the absorptive capacity of a series of elements with their atomic weights, Borodovskii came to the conclusion that the absorption of rays by a unit mass of some element distributed in a volume with a cross-section of \(1 \text{ cm}^2\) is directly proportional to the cube root of the atomic mass of that same element. The significance of the law he obtained, which we propose to call the “Borodovskii law,” was correctly assessed by the author himself. “Precise atomic weight conclusions cannot be calculated from this equation,” wrote Borodovskii, “but it may be used where it is necessary to establish the order of magnitude of an atomic weight.”

This law is well justified for chemical elements with medium atomic weight. Thus, for example, calculation of the atomic weight of fluorine according to the Borodovskii law, on the basis of data on the absorption of \(\beta\)-rays by fluorine, gives the value 18.94, which is in excellent agreement with the true atomic weight of fluorine, equal to 19.0.

From the Borodovskii law follows the possibility of determining the absorption of beta particles, proceeding from knowledge of the atomic weight. Borodovskii gives examples of such calculations and shows their good agreement with experimental data.

For the work “Absorption of Beta Rays” Moscow University awarded Borodovskii the master’s degree. At the invitation of Professor N. G. Egorov, V. A. Borodovskii moved to Petersburg and there took the position of senior inspector of the laboratory of the Main Chamber of Weights and Measures, where he began to develop a methodology for radioactive measurements. At the same time he began teaching a course on radioactive substances at Petersburg University.

At the Main Chamber of Weights and Measures, Borodovsky carried out the work “Radioactive Minerals of the Ilmen Deposits” ^9. An important practical result of these studies was the use of Russian euxenites for obtaining mesothorium. V. A. set himself the task of a broad investigation of the minerals of Russian deposits, which was to form the basis of his doctoral dissertation. Under the conditions of the old Russian reality, however, he did not receive the most necessary material support and, having overstrained himself, died on 28/I 1914.

In the obituary written by L. A. Chugaev, the death of the young talented scholar was noted as a grave loss not only for Petersburg University, but also for all Russian science.

L. S. KOLOVRAT-CHERVINSKY

Lev Stanislavovich Kolovrat-Chervinsky was born on 4/XII 1884. In 1900 he entered the Physics and Mathematics Faculty of Petersburg University, from which he graduated in 1904 with a first-degree diploma. L. S. was retained at the university to prepare for a professorship. For 2 years he conducted experimental work under Prof. Khvolson in molecular physics, after which he worked in the laboratory of P. Langevin and M. Curie-Skłodowska.

Returning to Petersburg, Kolovrat-Chervinsky passed the master’s examination and developed intensive scientific work. His activity took place at the Academy of Sciences, where he began to study Russian radium minerals in the laboratory of V. I. Vernadsky. From 1917 L. S. began working at the Main Chamber of Weights and Measures, where he also engaged in radioactive measurements.

In 1918 Kolovrat-Chervinsky defended a dissertation on the topic: “On the Release of Emanation from Solid or Molten Salts Containing Radium.” The dissertation was printed in the Proceedings of the Radium Expedition of the Academy of Sciences (1918, No. 9). Its length was 116 pages.

In this work Kolovrat-Chervinsky gave a new method of emanation measurements—the so-called melting method. Its essence consists in the fact that the substance under investigation, when subjected to melting, releases emanation, which is transferred into an ionization chamber. The ionization current was measured on an original electrometric apparatus using piezoquartz. The preliminary work on calibrating the instruments, in order to express the data obtained in absolute measure, was described by Kolovrat-Chervinsky in the work “On the Expression in Absolute Measure of Quantities of Radium Measured by the Emanation Method” (Proceedings of the Radium Expedition of the Russian Academy of Sciences, No. 10, 1918).

The melting method proved more reliable than the solution method, when substances are dissolved in acids and the emanation is extrac-

is carried away by a stream of air. Kolovrat-Chervinsky’s studies showed that the molten salt releases its emanation completely.

The fusion method found broad practical application. Kolovrat-Chervinsky himself, using it, successfully carried out a large number of determinations of radium in Russian minerals. The results of this excellent work were included in M. Curie’s well-known monograph Radioactivity. A summary of the results of this work was published in the Proceedings of the Congress on Radiology in Brussels.

In 1918 Kolovrat-Chervinsky was invited to the State Roentgenological and Radiological Institute to organize the radium department, and from that time on he was a full member of this Institute and head of the radium department. He took an active part in the radium expeditions of the Academy of Sciences and carried out numerous measurements of the radioactivity of waters and air in a number of places in the country. These studies were of great importance in prospecting for and discovering the radioactive riches of our Motherland.

While preparing volume V of his Course of Physics for publication, O. D. Khvolson entrusted Kolovrat-Chervinsky, as the foremost specialist in this field, with writing a separate chapter on radioactivity. In this chapter Kolovrat-Chervinsky gives an exhaustive account of the state of the question in 1913—1915.^13

On 24/I 1921 Kolovrat-Chervinsky died unexpectedly in the 38th year of his life.

At a meeting of the physics section of the Russian Physico-Chemical Society, O. D. Khvolson delivered a speech dedicated to the memory of his talented pupil. Khvolson gave a high appraisal of his scientific activity as a physicist-radiologist, calling him a “most profound expert,” an “outstanding representative of Russian radiology,” who had laid its firm foundations. Foreseeing the flowering of native radiology, Khvolson said: “the time of its flourishing will come. However it may flourish, the name of Lev Stanislavovich Kolovrat-Chervinsky will remain forever unforgettable in its history.”

In memory of the Russian radiologist, the nickel vanadium discovered by him, at the suggestion of Academician V. I. Vernadsky, was named kolovratite.^14

CITED LITERATURE

1. Vernadsky V. I., On the necessity of investigating the radioactive minerals of the Russian Empire. Notes of Academician Vernadsky, 2nd revised and supplemented edition, Publishing House of the St. Petersburg Academy, 1911.

1. Vernadsky V. I., Radioactive ores in the earth’s crust. Address delivered at a meeting of the Second Congress of Workers in Practical Geology, 27/XII 1911.

2. Vernadsky V. I., The task of the day in the field of radium, St. Petersburg, 1911. Proceedings of the Academy of Sciences, 1911.

3. Turkestan News, No. 243, 1913.

4. Fersman L. E., Works of the Radium Expedition, No. 2, 1914, St. Petersburg.

5. Khlopin V. G., The production of radium salts in Russia, Advances in the Physical Sciences, vol. III, issue 1922.

6. 25 Years of the Radium Institute, Publishing House of the Academy of Sciences of the USSR, 1947.

7. I. A. Antipov, On certain minerals from Russian deposits, Mining Journal, 1908, vol. IV.

8. Vremennik of the Main Chamber of Weights and Measures, series 2, part 1, 1916.

9. Borodovsky V. A., Absorption of beta rays of radium, Yuriev, 1910.

10. Vremennik of the Main Chamber of Weights and Measures, issue 1 (13), 1925.

11. Works of the Radium Expedition of the Academy of Sciences, No. 8, 1916; No. 9, 1918, and No. 10 for 1918.

12. Hvolson O. D., Course of Physics, vol. V, ch. XVIII.

13. Vernadsky V. I., On a new nickel mineral—kolovratite. Reports of the Academy of Sciences, 1922.