Production of Radium Salts in Russia

Vitaly Khlopin.

The question of producing radium salts in Russia arose quite some time ago, in 1908–1909, when the exploitation began of the uranium-vanadium deposit in the Fergana region of Turkestan, near the Tyuya-Muyun pass, 30 versts from the town of Skobelev, discovered by engineer Anturovich. This deposit was in the hands of a private company, at whose plant in Petrograd the extracted ore was processed for uranium, vanadium, and copper; the radium contained in it accumulated in the very valuable insoluble residues from production. In view of the high value of radium, the Company undertook laboratory experiments to find a suitable method for extracting this element from the accumulating production residues; however, the peculiar chemical composition of these residues—chiefly their unusually high content of silica (from 50–60%)—proved an unexpected and very serious obstacle, and all the Company’s work in this direction was unsuccessful. Having abandoned the idea of independently resolving the question of obtaining radium from the Fergana ore, the Company turned to foreign authorities in the field of radioactivity with a request that they undertake the processing, into radium, of the residues and ore in its possession. There is information that with this request it approached Mme. Curie in Paris, and that the latter recommended, as a specialist capable of resolving the question, one of her most talented pupils and collaborators, the now deceased Danne. After a series of experiments, the results of which remained unknown, Danne undertook to set up production; however, the conditions he put forward were not accepted by the Company, and the matter fell through. Later the Company attempted to interest specialists in Germany in this enterprise, among whom Professor Ebler of the University of Heidelberg in particular studied the radioactive residues of the Fergana Company in their chemical and technical aspects. He deemed the known methods of extracting radium unsuitable for their treatment and, for his part, proposed a new, very elegant method for processing radioactive ores rich in silica. From the autumn of 1914 it was proposed to organize the extraction of radium from the production residues

of the Fergana Society in Germany, using funds from the International Joint-Stock Company, into which the Fergana Society entered only as one of the shareholders. The war that broke out in July 1914 found the radioactive residues on the eve of their shipment from Petrograd to Germany, and thus this undertaking was once again disrupted. Interest in this question arose again in 1917, when, in connection with the needs of the military department for radium and after preliminary laboratory experiments on one of the varieties of radioactive residues, carried out by L. N. Bogoyavlensky on the one hand and by V. G. Khlopin on the other—experiments that made the possibility of extracting radium from them very probable—the organization of a special radium plant, under the direct control and direction of the Academy of Sciences, was recognized as necessary at the congress on the technical defense of the state in October 1917. The October Revolution again removed this question from the agenda, and only in the spring of 1918 did the Department of the Chemical Industry of the Supreme Council of the National Economy appeal to the Academy of Sciences with a request to undertake the organization of a radium plant. At the meeting held in March 1918 of the Commission for the Study of the Natural Productive Forces of Russia under the Academy of Sciences (KEPS), this question was resolved in the affirmative, and in July 1918 a special Commission, Technical Council, or later Collegium for the organization of a radium plant under the Academy of Sciences was elected, which entrusted the entire matter of organizing the radium plant and directing the work in this field to V. G. Khlopin. As manager of the plant, L. N. Bogoyavlensky, a specialist in this question, was invited. All radioactive residues located in Petrograd were evacuated from Petrograd into the interior of the country, first to the Berezniki soda plant in Usolye, Perm Province, and then, after this region had been cleared of Kolchak in May 1920, were transferred from there by the new manager of the plant, I. Ya. Bashilov, to the Bondyuzhsky chemical plant of Khimosnova, where only in the autumn of 1920 was it possible to begin organizing, first of all, a temporary experimental plant installation for the extraction of radium. Preliminary trial digestions had been carried out by me as early as August–September 1920 and gave very good results, which made it possible in July 1921 to put the installation into operation. By December 1, 1921, the question of the possibility of obtaining radium from the residues of the Fergana Society was, finally, resolved definitively, and I sealed the first high-activity radium preparation. In all, by December 15, about 10 milligrams of radium had thus been obtained in the form of a bromide salt, as high-activity preparations with a radium content of approximately 1–3%; about 8 milligrams in the form of poorer chlorides; and, finally, about 29 milligrams of radium metal in the form of a semi-finished product, i.e. barium–radium carbonates. The total quantity of radium extracted so far is thus estimated at approximately 45 milligrams of metal, of which, for the time being, in

in the form of more or less rich preparations supplied by me to Petrograd, about 13 milligrams calculated as metal were obtained at the Academy of Sciences. In conclusion I shall allow myself to dwell briefly on certain features of the method that had to be applied for extracting radium from our raw material, touching only on that part of it which, it seems to me, is of special interest also for physicists. It is well known that the only method so far for obtaining rich radium preparations, both on a technical and on a laboratory scale, is the fractional crystallization first of the chlorides and then, when the quantity of substance becomes small, of the bromide salts of barium-radium; in this process there occurs a gradual enrichment in radium in the less soluble portion of the crystals. Without giving here the well-known and classical scheme of Curie’s fractional crystallization, I shall indicate only that simplified variant which has recently been used in practice in the form in which it was also used at our plant (see drawing).

According to the same scheme a small crystallization of both chlorides and bromides also takes place; only the number of cups varies. Fractional crystallization may be carried out either in a neutral or in an acid solution; in the case of impurity of the barium-radium chloride compounds, crystallization in an acid medium is more desirable. The enrichment coefficient from cup to cup, as found for chlorides by Curie and for bromides by Giesel, in the best case, when dealing with pure barium-radium preparations, is 2 for chlorides and 4 for bromides. Usually, however, in industrial practice, where the chlorides are at first far from pure, the enrichment coefficient for chlorides, according to data of the American State Radium Institute, ranges from 1.5 to 1.6, and for bromides is 2–2.2. The presence of lead as an impurity has an especially harmful effect on the course of fractional crystallization. Foreseeing that in setting up fractional crystallization at the plant great difficulties would be encountered, in the sense of the impossibility at the present time of obtaining the necessary apparatus that would permit evaporation of acid chloride solutions, and wishing to come closer to the question of the chemistry of fractional crystallization, in the autumn of 1920 I proposed two topics—with the consent

Academician N. S. Kurnakov, in whose laboratory the work was carried out, assigned to two members of the Radium Collegium—A. S. Eliseev and P. A. Volkov: to the first, to study the system barium chloride, radium chloride, hydrochloric acid at \(t^\circ\) \(0^\circ\) and \(25^\circ\); to the second, the system barium chloride, radium chloride, lead chloride, hydrochloric acid at the same temperatures. In doing so I hoped that radium chloride would be distributed unevenly between the solid phase and the solution, becoming enriched in the solid phase upon its partial separation as a result of an increase in the concentration of hydrochloric acid, quite similarly to what takes place in fractional crystallization. In this way, by studying the distribution curve, one might hope to control the phenomenon of enrichment more precisely. The probability of such an assumption found confirmation in one of Prof. Ebler’s works, who observed that, by applying a current of gaseous hydrogen chloride to precipitate from an aqueous solution of pure barium-radium chlorides, it is possible to achieve a certain enrichment with radium of the precipitated barium crystals; namely, when approximately about 80% of all the barium present in the solution has been precipitated, practically all the radium (95–96%) is deposited with it.

Work on these studies was begun in January 1921; however, because of working conditions, by the time of my departure for the plant at the end of June 1921, it had been possible to study only the curve for the system: barium chloride—hydrochloric acid and barium chloride—lead chloride—hydrochloric acid, while the study of the system with radium had not yet been begun. Upon arriving at the plant, I, as was to be expected, encountered the impossibility of setting up fractional crystallization, since neither the appropriate vessels nor diluted steam were available in finished form, and therefore in August of the current year I personally urgently took up the study of the method of fractional precipitation of chlorides by hydrochloric acid in the cold, a method which could be carried out immediately. By mid-September the method had been developed in general outline, and from the end of October, under my direction, a temporarily installed plant apparatus, soon adjusted, was put into operation, making it possible by December to obtain the first radium-rich preparations. The study of fractional precipitation in the cold was conducted under the most primitive conditions, in the absence of a thermostat, so that the temperature was subject to considerable fluctuations (of several degrees); nevertheless, the data obtained gave very interesting results. It turned out that, in fractional precipitation of chlorides from an aqueous solution by the gradual addition of aqueous hydrochloric acid, regular enrichment of radium occurs in the first portions of the precipitated crystals, and the enrichment coefficient is a certain function of the relative amount of barium precipitated or, what is the same, of the concentration of hydrochloric acid in the solution, varying within the limits not of 1–2, as in the method of fractional crystallization, but of 1–3. At the same time, by precisely regulating the concentration of acid in the solution, one may, as desired, obtain any enrichment coefficient in this interval.

Finally, the presence of lead in this method does not prove especially harmful to the enrichment coefficient and, consequently, to the overall course of the work; moreover, the lead is continually enriched in the more sparingly soluble fraction of the crystals. Finally, with this method there occurs a simultaneous purification of barium-radium chloride from all impurities except lead. At the same time, the study of the phenomenon of fractional precipitation with hydrochloric acid now makes it possible to surmise the reason why, in the method of fractional crystallization, it was not possible to observe an enrichment coefficient greater than twofold. A detailed report on the work carried out at the plant, both on the technology of radium and on that of its valuable companions—uranium, vanadium, and copper (this last work was performed by the plant manager, I. Ya. Bashilov, and also yielded very interesting results)—will appear in the publications of the Academy of Sciences.

In conclusion, I shall point out that at the present time a permanent radium plant is being equipped, and it is proposed that a uranium-vanadium department be opened in the near future. The temporary installation is operating without interruption. The plant is under the jurisdiction of the Glavkhim of the V.S.N.Kh. and operates under the supervision and instructions of the Radium Institute of the Academy of Sciences; all radium produced is placed at the disposal of the Academy of Sciences.