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Home , Otto Berg (scientist), Rhenium, Technetium

Rediscovery of the Elements and III

Figure 1. The transition of the had all been discovered by 1923 except for the eka- manganeses (also known as “eka-” and “dvi-”Mn, “1” and “2” in ). Noddack and Tacke reasoned that these two elements might be found in ores (where the shaded blue elements may be found as 6 James L. Marshall, Beta Eta 1971, and impurities) and/or (Fe,Mn)(Nb,Ta)2O6 (red shaded elements). Their research showed that Virginia R. Marshall, Beta Eta 2003, element 75 (rhenium) is actually most commonly associated with in (see double 27,28 Department of Chemistry, University of headed arrow), corresponding to the “diagonal behavior” occasionally observed in the Periodic Table. North Texas, Denton, TX 76203-5070, [email protected] Figure 2. Ida Tacke and Walter Noddack in their laboratory at the After the 1923 discovery of ,1f only Physikalisch-Technische Reichsanstalt two transition elements were yet to be (PTR) in Berlin-Charlottenburg, discovered. These predicted elements (43 and established in 1887, where rhenium 75) were homologues of , the pre- was separated and characterized. dicted “eka-manganeses” of Mendeleev1c Noddack is posing with his ever-pre- (Figure 1). However, all attempts to find them sent cigar and is wearing his stained in crude manganese preparations ended in fail- laboratory coat proving that indeed ure.2 The problem of the missing elements was he was a dedicated bench-chemist. addressed in a comprehensive research project Photo, courtesy, Wesel Archives, by the husband-wife team of Walter Karl . Friedrich Noddack (1893–1960) and Ida Eva Noddack-Tacke (1896–1978) (Figure 2). The “work-unit” of Noddack and Tacke.3,4 Ida Tacke was born in Lackhausen (a suburb Curie — some German journalists have called Walter Noddack was born in Berlin and educat- of Wesel), a town on the Rhine River 85 kilo- her “die deutsche .”5 The story is ed at that city’s Friedrichs-Werdersche meters north of Köln (Cologne). She was the told that when Walter passed away in 1960, it Oberrealschule. This was the same prestigious daughter of Adelberg Tacke, the owner of a var- was because of an emotional heartbreak when institution where Friedrich Wöhler in 1828 dis- nish factory. Ida was educated at the Berlin he heard (incorrectly) that his wife, unreachable proved the theory of “vital force” in organic Hochschule, earning her doctorate in engineer- by telephone, had died during an illness in compounds by isomerizing ammonium iso- ing (Doktor-ingenieur) in 1921.3 She special- Hamburg.3 cyanate into urea.1a Noddack then matriculated ized in organic chemistry, thinking that she at the University of Berlin and obtained his could improve the curing behavior of linseed oil The search for the missing elements. doctorate in 1920. His advisor was Walther in her father’s business. After her graduation, Noddack and Tacke observed that odd-atomic Nernst (1864–1941; Nobel laureate in chem- however, she met Walter and was smitten by his number elements were less abundant than istry, 1920), who formulated the third law of quest for new elements. She joined the even- elements.6 Thus they real- thermodynamics. When Nernst left to accept Physikalisch-Technische Reichsanstalt in 1922 ized that the eka-manganeses might be partic- the presidency of the Physikalisch-Technische and they married four years later. The two ularly rare, and that a very meticulous and Reichsanstalt (Figure 3) in 1920, Noddack researchers formed, as she called it, the methodical search might be necessary to dis- moved with him. Three years later, Noddack Arbeitsgemeinschaft (work-unit)3 that held them cover them. The team reasoned that since the became the new head of the Anstalt. It was here together through mutual research and love in a eka-manganeses had not been found in nature that he met Ida Tacke. manner reminiscent of Pierre and Marie with the parent element 25, they should search

84 THE HEXAGON/WINTER 2013 Figure 4. One of the more prolific sources of rhenium-bearing is Knaben, Vest- Agder, Norway, where a historic mine is located (N58° 39.55 E07° 04.41). This mine provided strategic molybdenum used in armament for the WWII Nazi effort and was bombed twice by the allies in 1943. Note the snow in the foreground despite the summer date (June 30).

ABOVE: Figure 3. The chemistry building (Chemie Gebäude) of the PTR is now used for administration purposes. The name of the PTR was changed to the Physikalisch-Technische Bundesanstalt (Physics-Technical Federal Institute) in 1945. Presently, among other responsibilities, the Bundesanstalt is accountable for atomic clock standards in Germany. Inset: The Waffen (icon) as it appears at the entrance of the Anstalt, Abbestraße (2-12, N52° 30.98 E13° 19.26), Charlottenburg, West Berlin.

RIGHT: Figure 5. The talus scattered about at Knaben, Norway— 900-million-year-old Precambrian granitic gneiss — is profuse with molybdenite that looks like splashes of solder. The molybdenite is rich in rhenium, with concentrations as high as 7.5 ppm.7 Historically, molybdenite, native , and graphite were all con- fused with one another; Scheele distinguished the three in 1779.1b Molybdenum is named after the Greek word for lead (molybdos).1b

in platinum and columbite ores, in which many ic number, they identified lines from elements confirmed element 75 (rhenium).8 Rhenium low-concentration elements had already been 43 and 75. They claimed the discovery of two was the last naturally-occurring element to be observed (Figure 1). Ida took a full year’s sab- new elements,6 which they named masurium discovered (Note 1). batical to conduct a thorough literature search (Ma) and rhenium (Re), respectively (after Unfortunately, the Noddacks could not to develop a complete repertoire of chemical regions in Prussia and the Rhineland). So far reproduce the results for element 43 (masuri- separation procedures to help them in their they could not obtain either element in weigh- um). Unknown to them, element 43 has no sta- quest. able quantities. ble , and its discovery had to await Working with a variety of platinum and After their marriage, Noddack and Tacke nuclear synthetic procedures (vide infra). columbite samples, in 1925 they obtained a traveled to Scandinavia to find richer sources of In 1935, the Noddacks moved from Berlin to white sublimate (Re2O7). Collaborating with rhenium; they procured ore samples from 124 Freiburg, then in 1941 to Strassburg after (1873–1939) of Siemens & mines in Sweden and Norway.7 An analysis of Germany annexed the region (Strassbourg in Halske1h— whose laboratories were conve- these indicated relatively large amounts of rhe- French), and finally the University of Bamberg niently located only 400 meters north — Tacke nium in molybdenite (MoS2) in several of the in 1946, where he founded the Staatliches recorded the X-ray spectra of their prepara- Norwegian sites7 (Figures 4, 5). In two years Forschungsinstitut für Geochemie (State tions. Based on the work of Moseley1e which they were able to isolate 1 gram of rhenium Research Institute for ) (Note 2). predicted the X-ray frequencies based on - from 660 kg of molybdenite, whose X-ray lines As an outgrowth of their search for the eka-

WINTER 2013/THE HEXAGON 85 III ments” “new radioactive ele- Nobel PrizeinPhysics for Fermi (1901–1954)was awarded the1938 failure towinthisprize. inability toverifymasuriumcontributedtheir were notsuccessful. Itissuggestedthatthe times fortheNobelPrize, butunliketheCuries retired in1956. the occurrence ofallknownelements. Walter whenever Walter would remind OttoHahn and Fritsch. announcement ofHahn, Strassman, Meitner, ments. check theproduct mixture forall ments would becreated andoneshould laboratory, shesuggestedsmalleratomicfrag- was creating transuranium elements inFermi’s sensus thatneutron bombardment ofuranium clusions. Refusingtoacceptthegeneral con- correctly challengingtheItalianscientist’s con- fission she actuallyproposed theconceptofnuclear 86 chen Elementen”) the ’s crust(“DieHäufigkeitderchemis- ed theconceptof “elemental abundances” in manganeses, Idaand Walter Noddackoriginat- plaques, seeNotes2and3). constructed byAndreas Krämmer. (For other This two-metermonument, erected in2006, was Noddack-Straße (N51°40.70 E06°37.96). stands inherhometownof Wesel onIda- Figure 6. This bustofIdaNoddack-Tacke bronze The Noddackswere nominatedseveral 12a 12 11 In herarticle “Über dasElement93,” as IdaNoddack-Tacke (Figure 6)was five years before thedramatic 13 During theperiod 1935–1938, 9 and produced estimatesfor 3,10 It isironic thatEnrico known ele- first heavy nuclei” in Chemistry for “his discovery ofthefission paign ifHahn, winnerofthe1944NobelPrize the possibleoutcomeofGermany’s WWII cam- masurium research. Itissoberingtoreflect on all”!) hatte dochRecht.” (“. . . andIdawas rightafter “. . . unddieIda 1966, Hahnfinallyadmitted, was 30years later, duringaradio broadcast in had notignored Tacke’s earlysuggestions. It npoim”“neomolybdenum,”“nipponium,” “moselium,” “ilmenium,” “pelopium,” “davyum,” “lucium,” have beenproposed, including “polinium,” ment betweenmolybdenumand ” netium. h icvr feeet4 —tech- The discoveryofelement43 is enough”!), “Ein Fehlerreicht”the ideawith (“Onemistake , Hahnwould abruptlydismiss (1879–1968) ofIda’s suggestionsregarding 4a 16 Many historicclaimsfor “the ele- 15 14a at theKaiser Wilhelm Institut, referring totheNoddacks’ involving plutoniuminatomicbombs. Segrè playedacriticalroleintheManhattanproject, solvingproblems States in1938, followedthenextyearbyhiswifeElfriedenéeSpiro. inPhysicsPrize in1958. SegrèmovedpermanentlytotheUnited Owen Chamberlain(1920–2006), withwhomheshared theNobel later atBerkeleywasco-discoverer oftheantiprotonin1955with Figure 7. EmilioSegrèwasco-discoverer oftechnetium(1937)and building wasdemolishedin1959andreplaced byLatimerHall. Testing Laboratory, builtin1885(N37°52.40 W122° 15.37). The was putintooperation in1931, refurbished from theCivilEngineering Lawrence (latermodifiedtoa37-inchinstrument). This laboratory California-Berkeley housedthe27-inchcyclotroninventedby Figure 8. The “Old RadiationLaboratory” attheUniversityof ments. until theadvent oftheartificiallyproduced ele- the discovery oftechnetiumwas notpossible stable isotopeofelement43is earth’s crustinappreciable quantities. The most explorers, thiselementdidnotexistinthe creation oftheearth4.6x10 dial element43shouldbelonggonesincethe nuclear reactions involving slowneutrons. In of Fermiwhowere pioneering thefieldof boys,” agroup ofscientists undertheguidance (1932), where hejoinedthe “Via Panisperna fessor ofphysics attheUniversityofRome a shortstintinthemilitary, Segrèbecamepro- 7) was bornin Tivoli, 26kmeastofRome. After Fermi attheUniversityofRome. Segrè(Figure (1905–1989) was beginninghisstudieswith gram ofrhenium, EmilioGinoSegrè half-life of4.2x10 While theNoddackswere isolatingtheirfirst and “masurium.” THE HEXAGON/ 16 6 Unbeknownst tochemical er andany primor- years — 9 years ago. Hence, WINTER 2013 43 Tc 98 with a ABOVE: Figure 10. The magnet used for the 27-inch (opera- tional 1932), then modified to the 37-inch cyclotron (operational five years later), is now standing outside the Lawrence Hall of Science. The Figure 9. Ernest Orlando Lawrence (1901–1958; Nobel Prize in Physics in 1939) magnet, originally built for power communication between the U.S. and invented the cyclotron in 1931, and improved its design and size through the coming Europe in World War I, was acquired by Lawrence as war surplus. years. A museum devoted to him—the Lawrence Hall of Science—is the best place to be introduced to the extraordinary history of at Berkeley. This BELOW: Figure 11. On Via Archirafi 36, Palermo, Sicily, , is the old museum is on Centennial Drive in the Berkeley Hills (N37° 52.77 W122° 14.80) Experimental Physics Building (N38° 06.61 E13° 22.39), where tech- overlooking the University of California at Berkeley. The museum was established in netium was discovered. The first two floors housed physics, and the top 1982 by Glenn Theodore Seaborg (1912–1999; Nobel Prize in Chemistry 1951; 〈⌾⌺ floor housed mineralogy. The building is now used for library resources, - Beta Gamma ’35, John R. Kuebler Award, 1978). storage, and the Mineralogy Department. (The modern science buildings are at the new campus on Viale Delle Scienze, 2.2 km to the west.)

1936, Segrè became professor and director of the Department of Physics at the University of Palermo. During a visit to Berkeley in 1936, he became curious about the possibilities of trans- mutations occurring in the cyclotron (Figure 8) invented by E. O. Lawrence (Figure 9). He returned to Palermo with scrap pieces which had been radiated from which he isolat- ed several radioactive elements, including sul- fur-32. In February 1937 in Palermo, he received from Berkeley a radioactive strip of molybde- num foil used as a deflector plate in the 37-inch cyclotron (Figure 10). Since the molybdenum 2 had been bombarded with deuterons (1H ), Segrè “suspected at once that it might contain element 43,”17 next to molybdenum in the Periodic Table. Segrè needed chemical expertise, and he was fortunate that his university building (Figure 11) housed the institutes of both physics and mineralogy. The head of mineralo- gy was Carlo Perrier (1886–1948) (Figure 12), an Italian mineralogist well versed in the classical ammonia to remove the surface impurities, were individually isolated, but none showed analytical procedures in chemistry. In their sep- where the nuclear reactions would have radioactivity. To the remaining radioactive aration procedures, Segrè and Perrier followed occurred. Because of the anticipated small solution they added a rhenium (75) carrier -10 18 the radioactive material in their separations amounts of product (less than 10 gram, ) to which was precipitated by H2S. This radioactive using the manner pioneered by the Curies the extracted solution, they added various carri- rhenium () carrier was converted to the when they first separated polonium and radi- ers — (at. no. 40), (41), with peroxide and distilled to um.1d First, they reacted the Mo foil with boiling molybdenum (42), and manganese (25). These remove the volatile rhenium oxide, which

WINTER 2013/THE HEXAGON 87 LEFT: Figure 12. Carlo Perrier, head of the Mineralogy Institute, worked out the chemistry of technetium19,29 which allowed its isolation. Despite the impor- tance of his work which allowed the dis- covery of the first artificially produced element, Perrier never received the Nobel Prize. RIGHT: Figure 13. Prof. Arturo Russo, of the Dipartimento di Fisica e Tecnologie Relative, Università di Palermo, was the host of the authors during their visit to Palermo. Dr. Russo is interested in the science history of his university. From forgotten storage items he has found the III old equipment used by Emilio Segrè. Russo is holding the ionization chamber constructed by Segrè.

exhibited no radioactivity. The remaining pute as to whether or not the Noddacks ever radioactive solution was concluded to contain could have detected element 43 in their prepa- element 43 —but without weighable amounts rations. The short half-life of technetium pre- isolated and without an X-ray spectrum19 cludes its presence on earth except in radioac- (Figure 13). tive ores where secondary processes have Segrè promptly visited the Noddacks, now occurred since the creation of the earth.23 A in Freiburg (September 1937). Segrè, who subsequent careful analysis has shown that the the Russian muraled Periodic Table, while “Il” spoke excellent German, wished to give credit low concentration of in the remains. One might suspect political reasons where it was due. He wanted to establish Noddacks’ material would not have produced are responsible for this removal of “Ma,” since unequivocally whether he had simply con- detectable amounts of technetium by their X- the Battle of the Masurian Lakes in World War I firmed the existence of “masurium,” or whether ray analysis.24 was a victory for Germany over Russia. Some he was actually the first to observe element 43.17 The struggle for priority of the discovery of believed the Noddacks chose the name for According to Segrè’s account17 Walter was non- the elements has often been contentious. In a nationalistic reasons, despite the Noddacks’ committal and could not produce the X-ray 1947 editorial by Friedrich Adolph Paneth insistence it was done in recognition of his plates of masurium, which he said “had acci- (1887–1958) in Nature, this “speaker of father’s homeland (East , then dentally been broken.” Obtaining no definitive authority”1a wryly noted, “. . . the slowness of Prussia).14a information, Segrè concluded that at the very chemists in taking the obvious action of aban- In defiance of the general rejection of least, the Noddacks had “no clear-cut results” doning suggested names is due to the failure of masurium by the scientific community, a plaque and that if their claims were indeed lacking, the claimants to withdraw their statements, on Ida’s old homestead in Wesel (Note 3) bold- they would probably “fall of their own although during years of intensive effort they ly proclaims [translated] “. . . This worldwide weight.”17 Two weeks later, the Noddacks and had been unable to substantiate them. In the famous woman chemist discovered and colleagues, outfitted in uniforms with case of masurium, W. Noddack even went so far described in 1925, together with her husband, swastikas,14a appeared at Segrè’s laboratory in . . . as to complain to the convener of a chemical rhenium and masurium (today known as tech- Palermo; Segrè showed them his results and meeting in Königsberg for not having invited netium . . .).” they left without comment. No more personal him to speak on this element, as . . . he would contact occurred between Segrè and the have been in a position to disclose the whole Acknowledgements. Noddacks. chemistry of masurium . . . but no communica- Subsequent work with the cyclotron at tion has ever appeared on this work.”20b The authors are indebted to Dr. Hans Georg Tilgner of Wesel, Germany, local expert Berkeley allowed material to be produced Despite the lack of further proof of masuri- 4 whose X-ray spectrum confirmed element 43. um, the most “up-to-date” Periodic Table in the on the Noddacks and author of Forschen, By the early 1940s, it was generally agreed that late 1920s and early 1930s was the Antropoff Suche und Sucht [Research, Quest, and element 43 is “missing from our earth”20a (tech- Periodic Table (highlighted in the previous issue Obsession], for his generous help of informa- netium has since been detected in the spectra of of The HEXAGON 1i ) which proudly proclaimed tion and photographs regarding the discovery stars21) and in five years a protocol was suggest- “Ma” as element 43. The “largest Periodic Table of rhenium, particularly that dealing with the ed for the naming of artificial elements.20b In in the world,” constructed in 1935 on the wall of hometown heroine Ida Tacke. 1947, a publication appeared in Nature dubbing the Metrology Institute in St. Petersburg,1c the first artificial element, atomic number 43, as included not only masurium (43) but also illini- Notes. technetium.22 um (61), both spurious elements which at that NOTE 1. A claim was made in 1908 for a new 25 Could the Noddacks have observed tech- time were erroneously “firmly rooted in text- element nipponium found in thorianite (ThO2) 20b netium? Ever since Perrier and Segrè’s books and tables.” It is interesting to note by a Japanese chemist, Masataka Ogawa announcement in 1947, there has been a dis- that the original tiled “Ma” has been scraped off (1865–1930), in the research group of Sir

88 THE HEXAGON/WINTER 2013 William Ramsay (1852–1916, Nobel laureate in 10. M. F. Rayner-Canham and G. W. Rayner- 20. F. A. Paneth, Nature, (a) 1942, 149, 565–568; Chemistry, discoverer of the noble gases.1g) Canham, ed., A Devotion to their Science. (b) 1947, 159, 8–10. Ogawa placed the element between molybde- Pioneer Women of Radioactivity, 1997, 21. B. T. Kenna, J. Chem. Ed., 1962, 39(9), num and ruthenium in the Periodic Table, i.e., “Ida Tacke Noddack,” F. Habashi, 217–225, 436–442. element 43, or present-day technetium. Upon Chemical Heritage Foundation, returning to Japan, Ogawa isolated what he Philadelphia. 22. C. Perrier and E. Segrè, Nature, 1947, 159, 24. This article, dealing with the naming of thought to be the same element from Japanese 11. http://www.nobelprize.org/nobel_prizes/ 25 technetium, is immediately followed by molybdenite. H. Kenji Yoshihara (1929– ) long physics/laureates/1938/ after Noddacks’ work, suggested that Ogawa in the announcement of element 85 astatine, fact had rhenium,26, 27 which probably was true 12. (a) I. Noddack, Angewandte Chemie, 1934, produced by treating bismuth with alpha based on an analysis of the Noddacks’ world- 47, 653–656. (b) An excellent review of particles with the new 60-inch cyclotron wide analyses7 which showed Japanese molyb- “the detours leading to the discovery of (D. R. Corson, K. R. Mackenzie, and E. denite to be the richest they ever studied (9.8 nuclear fission” is laid out in K. Starke, Segrè, idem). ppm Re). J. Chem. Ed., 1979, 56(12), 771–775. 23. A. M. Hayashi, Scientific American, 2000, NOTE 2. A plaque devoted to Walter Noddack 13. O. Hahn and F. Strassman, 282(2), 18. resides at Künstlerhaus, Villa Concordia, Naturwissenschaften, 1939, 27(1), 11–15; 24. (a) F. Habashi, J. Chem. Ed., 2006, 83(2), Concordiastraße 28, Bamberg (N49° 53.28 E10° L. Meitner and O. R. Frisch, Nature, 1939, 213; (b) R. Zingales, letter, idem. 143(3615), 239–240. 53.31), in honor of his accomplishments in geo- 25. H. K. Yoshihara, Spectrochimica Acta, Part B, chemistry. 14. R. L. Sime, . A Life in Physics, 2004, 59, 1305–1310; Proc. Jpn. Acad., Ser. B, 1997, U. of California Press (a) 271–273; NOTE 3. The old Tacke home in Wesel (“Haus 2008, 84, 232–245. (b) 464. Wohlgemuth”) is located at Brüner Landstraße 26. For a full discussion of nipponium, see 301 (N51° 41.04 E06° 39.12), beside the Brüner 15. http://www.nobelprize.org/nobel_prizes/ M. Fontani, M. Costa, and M. V. Orna, Lackhauser Farben (paint store), on the site of chemistry/laureates/1944/hahn-bio.html The Lost Elements: Errors, Retractions, and the original varnish factory established in 1867. 16. R. Zingales, J. Chem. Ed., 2005. 82(2), Dead Ends in the Creation of the Periodic A plaque was erected in 2006, which describes 221–227. This is arguably the best article Table, 2014, (in press). her major accomplishments, notably the dis- on the discovery of technetium, and is the 27. E. Scerri, A Tale of 7 Elements, 2013, Oxford, covery of rhenium and masurium, and her 1934 source for most of the information herein. idea of the splitting of the uranium atom by 109–114. bombardment. 17. E. Segrè: A Mind Always in Motion. 28. E. Scerri, The Periodic Table. Its Story and its The Autobiography of Emilio Segrè, 1993, Significance, 2007, Oxford, “Diagonal References. U. of California Press, 112–117. Behavior” 265–267. 18. E. Segrè, Nature, 1939, 143, 460–461. 1. J. L. Marshall and V. R. Marshall, 29. C. Perrier and E. Segrè, Rend. Lincei, The HEXAGON of Alpha Chi Sigma, (a) 2004, 19. C. Perrier and E. Segrè, J. Chem. Phys., 6th ser., 1937, 25, 723–730; 27, 579–581. 95(3), 46-50; (b) 2005, 96(1), 8-13; (c) 2007, 1937, 5, 712–716; 1939, 7, 155–156. 98(2), 23-29; (d) 2010, 101(1), 6-11; (e) 2010, 101(3), 42-47; (f) 2011, 102(3), 36-41; (g) 2012, 103(3), 36-41; (h) 2013, 104(3), 46-51; (i) 2013, 104(3), 65-66, 69. 2. L. C. Hurd, J. Chem. Ed., 1933, 10(10), 605-608. “REDISCOVERY” ARTICLES ARE NOW ON-LINE

3. A. Lykknes, D. L. Opitz, B. Van Tiggelen, ed., All HEXAGON issues that include “Rediscovery” articles— a series which began in 2000—are For Better or For Worse? Collaborative Couples now on-line at the University of North Texas Digital Library, found at: in the Sciences, 2012, Birkhäuser, 103-123. http://digital.library.unt.edu/explore/collections/HEXA/ 4. H. G. Tilgner, Forschen, Suche und Sucht, 1999, Libri Books; (a) p 216. These HEXAGON issues, as a group, are fully searchable and thus are amenable to scholarly 5. Schubert, Fritz, Die “deutsche Marie Curie”; research. One can search either for words, Boolean “OR” combinations, or for full phrases (by Rheinischen Post, Berühmte Niederrheiner, placing in quotation marks). Not only the original “Rediscovery” articles may be accessed, but 36. Jg., Düsseldorf, 15. August 2009, S. B 6. also cover photographs by the authors and other auxiliary articles connected with the 6. W. Noddack, I. Tacke, and O. Berg, “Rediscovery” project. Naturwissenschaften, 1925, 13 (26), 567–574; [English summary] Nature, 1925, 116, 54–55. Additionally, the UNT Digital Library has separated out all these individual articles and 7. I. and W. Noddack, Das Rhenium, 1933, placed them in the “Scholarly Works” section. These articles may be located and perused at: Leopold Voss, Leipzig. http://digital.library.unt.edu. At the top of the webpage, search for “James L. Marshall” as 8. I. and W. Noddack, Z. anorg. allgem. Chem., “creator” and for convenience, “sort” by “Date Created (Oldest).” The “Scholarly Works” 1929, 183, 353–375. articles are not searchable as a group, but only within each individual article. 9. I. and W. Noddack, Die Naturwissenschaften, 1930, 18, 757–764.

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