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WHAT'S BEEN GOING ON
"HELVETIUM AND "MOLDAVIUM," ELEMENTS 85 AND 87?
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NNOUNCEMENTS of the "discovery" of the elements of atomlc numbers 85 and 87 have appeared from time to time &ring the past fifteen years, but until recently none has been confirmed.' At present, the evidence for the occurrence in nature of both elements 85 and 87 is very convincing, and the chemistry of element 85 has been investigated by means of a radioactive isotope, produced artificially.
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ELEMENT
85
Carson, Mackenzie, and Segr*, of the University of California, announced at the Washington Meeting of the American Physical Society, April. 1940, that the artificially radioactive element 85 is produced by bombarding bismuth with 32-Mev. alpha particles.' The behavior of the product is complex: by the emission of alpha particles, forty per cent of it reverts to bismuth, but due to the emission of neutrons in the original impact the isotopic species produced differs from that of the target, in that it probably has a mass number of 207 and is radioactive. By the capture of a K-shell electron, sixty per cent of it is transmuted into AcC', a known isotope of polonium. These nuclear reactions may be summarized as follows:
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srBimp z H ~-'r *[85lST1 2n 40%
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- *[85Iz1'
7.5 hours
*srBi207f ,He4 60% - *[85In' 4- r- + $~AcC'~''
ELEMENT
87
In 1914. St. Meyer, Hess, and Paneth4 reported that although actinium normally emits beta rays, it is also feebly alpha-ray active, emitting particles of 3.5 on.air penetration. For several years this activity was explained as being due to the presence of
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The names "alahamine" and "virginium" have not been generally accepted and the "magneto-optic effect" of Professor Allison of Alabama Polytechnic Institute is at present not considered to have any physical significance, cf. COMSTOCK, Phys. Rev., 51, 776 (1937). CORSON, MACKENZIE, AND SEGRI?, ibid., 57, 1087 (June 1. 1940). Vf, also T-ER, Pkyr. Rev.. 58, 181 (July 15, 1940). Wiener Ber., 123. 1459 (1914).
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traces of protactinium. On January 9. 1939,' Mlle. Marguerite Perey confirmed the earlier explanation and announced that the product of the disintegration. AcK. was a natural radioactive isotope of element 87. Using lanthanum as the carrier for the actinium, the latter was freed of all its known radioactive neighbors and showed negligible activity. During the two hours following the purification, the beta-ray activity rose abnormally and this behavior was explained by the presence of a new element, AcK, with a half-life period of 21 minutes. Using cesium as a carrier, the chemical properties of AcK were investigated and found to be those of an alkali metal; thus, it is not precipitated by hydrogen sulfide, but is carried dawn as the perchlorate. I t is readily separated from second, third. and fourth group elements. being dissimilar to barium, cerium, and lead. Hulubei announced that by a very On June 8, 1936,"oria sensitive X-ray spectroscopic method, he has demonstrated the presence of element 87 in the alkali metal salt concentrate extracted from pollucite. Since his original work, he has taken great precautions to eliminate the possibility of false identification of the spectral lines and has repeatedly confirmed his findings. using different samples, various spectrographs equipped with crystals of either quartz or mica. and by working in several spectral orders. Furthermore, he believes he has shown that element 87 is concentrated in the mixture of alkali metals by the lower solubility of its chloride in alcohol. Of the minerals, beryl, lepidolite, pitchblende, pollucite, soddite, and Bavarian autunitesolombite, the first two gave negative results and the last the greatest prospects for its isolation. Hulubei claims the discoverv of element 87 and has .orooosed . the name "moldavium" (.MI) in thcse words:' "Pour cet Cl6ment 87, j'ai propose le "om de moldomurn (MI) en homage A la Moldavie, province roumaine, marche avanck v u s 1'Est dt: la latinit&" If the results of the investigations of both MUe. Perey and Hulubei are verified, a t least two isotopes of element 87 must occur naturally, one with a long life and the other with a transitory existence. -LAURENCE S. FOSTER ~
Because of the radioactivity of the isotope of element 85, it has been possible to trace through some of its chemical reactions. I t appears to be more markedly electropositive than the other halogens; it is precipitated, for example, by hydrogen sulfide from a solution 6Nin hydrochloric acid. but is not precipitated by silver nitrate from its solution in nitric acid, when iodide is used as a carrier. I t does, however, appear to be quite volatile, since the bombarded bismuth loses its activity below 275'C. It has also been reported that element 85 is concentrated in the thyroid. In an Associated Press release, dated July 24, it was announced from Bern, Switzerland, that Dr. Walter Minder, chief of the Radium Institute of Bern. has isolated element 85 and named it " h e l v e t i u m . " ~ i s claim to its discovery may, however, be disputed by Hulubei and Chauchois, who reported in July, 1939. that they had detected X-ray spectral lines, an excitation of the disintegration products of radon, which could be associated only with element 8 8 . Though predominantly an alpha-ray emitter. radon possibly emits beta rays also, and is thus transmuted to element 85. Until Minder's data are published, judgment as to the priority of the claims must be reserved.
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ROM the Arthur D. Little laboratory comes the announcement that electrolytic polishing is now taking its place with surface coatings and mechanical methods far producing smooth. Essentiallv the oo~osite of electrolustrous ~~~~~~-~metal surfaces. .. plating, the new method depends upon metal removal. Metals are immersed in a bath, usually acidic, and electric current opposite in direction to that for electroplating is applied. The surface starts to dissolve and, under proper conditions, a dull and non-reflecting surface becomes much more lustrous and mirrorlike, as if mechanically buffed or burnished. In some instances, particularly with stainless steel, this anodic luster h i s h suroases in dmth of tone and hrilliancv that obtained bv mechanical polishing. The treated surface is claimed to be an excellent base for subsequent electroplating and even to give improved resistance to corrosion. Theories explaining the action difler, but all agree that the net result b a preferential attack on the high protruding parts of the metal surface, which results in leveling and smoothing. One plausible theory suggests the formation of a a m over the metal surface which covers and oratects the low parts but exposes the PEREV,Comfit. rend., 208, 97 (1939); J. Phys. Radium, 10, 435 (1939). 6 H U L ~ E ICompt. . rend., 202, 1927 (1936); cf.
