Soddy, Frederick
Frederick Soddy. Wikimedia Commons (Public Domain)


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Soddy, Frederick


(b. Eastbourne, England, 2 September 1877; d. Brighton, England, 22 September 1956)

radiochemistry, science and society.

Soddy developed with Lord Rutherford during 1901–1903 the disintegration theory of radioactivity, confirmed with Sir William Ramsay in 1903 the production of helium from radium, advanced in 1910 the concept of isotope, proposed in 1911 the alpha-ray rule leading to the full displacement law of 1913, and was the 1921 Nobel laureate in chemistry, principally for his investigations into the origin and nature of isotopes.

The youngest son of a London merchant, Soddy was raised in the Calvinist tradition by his dominant half-sister. He developed a lifelong sense of extreme social independence, as well as a plague-on-both-your-houses attitude toward religious controversy, later extended to social institutions in general. An aspiring scientist from an early age, Soddy was encouraged by his influential science master, R. E. Hughes, at Eastbourne College to study chemistry at Oxford. After an interim year at coeducational Aberystwyth, Soddy in 1895 received a science scholarship to Merton College, Oxford. In 1898, with Ramsay as external examiner, Soddy received a first-class honors degree: he remained at Oxford for two more years, engaged in independent chemical research.

In May 1900, Soddy adventurously followed up an unsuccessful application to Toronto, with a personal visit to Montreal, accepting a position as demonstrator at McGill University. His childless marriage in 1908 to Winifred Beilby (d. 1936) was a source of great happiness and stability in his life. Soddy was “an admirable writer and a clear and interesting lecturer,”1 noted for originality in demonstrations. A fellow of both the Chemical Society (from 1899) and the Royal Society (from 1910), Soddy was also a foreign member of the Swedish, Italian, and Russian academies of science. In 1913 he was awarded the Cannizzaro Prize for his important contributions to the new chemistry.

Profoundly disturbed by World War I and “enraged”2 by the death of Moseley, Soddy felt that society was not yet sufficiently mature to handle properly the advances of science. He began to concern himself more with the interaction between science and society. In order to ascertain “why so far the progress of science has proved as much a curse as a blessing to humanity,”3 Soddy studied economics. He considered the free development of science to be the new wealth of nations and advocated the rise of a “scientific civilization.”4 The “curse” he felt arose from constraints, put upon both the progress of science and the distribution of technological productivity, for the self-maintenance of the existing but decadent economic system.5

At McGill, Soddy joined with Rutherford in a series of investigations which produced the theoretical explanation of radioactivity. The constant production of a material “emanation” from thorium was shown to be the combined effect of the production of an intermediate, but chemically separable, substance, thorium X, balanced by its decay. The production of one substance was thus the result of the uncontrollable disintegration of another. The “radiation” proved to be both particulate in nature and a direct accompaniment of the process of disintegration. The rate of the process was found in every case to be as the exponential law of a monomolecular chemical reaction. So complete was their 1903 disintegration theory of radioactivity, that in 1909 only an extension to branching series was required.6

In March 1903, Soddy elected to join Ramsay in London to examine more fully the gaseous products of decay. Using Giesel’s radium preparations, Ramsay and Soddy experimentally confirmed in July 1903 the prediction of Rutherford and Soddy that radium would continuously produce helium. In 1908 Rutherford “settled for good”7 the longsuspected identity of the helium, so produced, with expelled alpha particles. During the ten-year period following his 1904 appointment to the University of Glasgow, Soddy helped to clarify the relation between the plethora of radioelements and the periodic table.

McCoy and Ross had reported in 1907 that Hahn’s 1905 radiothoriurm was chemically inseparable from thorium. Boltwood, in turn, indicate a similar difficulty with thorium and ionium. From crystal morphology studies, Strömholm and Svedberg in 1909 confirmed a family resemblance between such radioelements as thorium X and radium. In 1910 the chemical inseparability of mesothorium 1 and radium, reported by Marckwald, as well as Soddy’s own experimental evidence, that these two radioelements form an inseparable trio with thorium X, convinced Soddy that such cases of chemical inseparability were actually chemical identities. Without the unnecessary continuation of the genetic series of radioelements throughout the entire periodic table, postulated by Strömholm and Svedberg, Soddy declared in 1910 that “the recognition that elements of different atomic weight may possess identical chemical properties seems destined to have its most important application in the region of the inactive elements.”8 “Soddy possessed.” as Hahn wrote in admiration,9 “the courage to declare that these were chemically identical elements.”

To be able to refer generically to these active and inactive elements with identical chemical properties, Soddy introduced the technical term “isotope” in 1913.10 While chemically inseparable, active isotopes were distinguishable by their radioactive properties, and all isotopes differed in atomic weight. Soddy suggested that the 1912 metaneon of J. J. Thomson be considered “a case of isotopic elements outside the radioactive sequences.”11 Following Soddy, Aston announced a partial separation in 1913 on this very basis.12 The connection between chemical properties and the periodic table became increasingly clarified with concurrent developments in the physics and chemistry of the nuclear atom, from the chemical side. Soddy proposed the alpha-ray rule in 1911, the key to the first of two locks. Applying his general principle that the common elements are mixtures of chemically inseparable elements “differing step-wise by whole units of atomic weight”13 specifically to the case of the radioelements, Soddy recognized that the expulsion of an alpha particle would result in a lighter element chemically inseparable from those occupying the “next but one”14 position in the periodic table. The second lock to the displacement law involved the beta transitions.

During 1912 Soddy assigned Lord Fleck the task of sorting out the short-lived beta emitters, especially at the complex branching points in the series. Once these experimental results became available, several partially correct generalizations were published, inducing Soddy. therefore, to publish his own complete and correct form of the law in February 1913. “Fajans,” Soddy acknowledged, “worked out the Periodic Law Generalization quite independently of me,”15 although his conclusions were fundamentally different. On electrochemical considerations. Fajans interpreted the changes among the clusters, “plejade,”16 of radieoelements as evidence against the nuclear origin of radio-changes.17 Soddy. on the other hand, argued for a crucial distinction18 between radiochange and chemical change, concluding on chemical evidence, as Bohr had done on physical evidence. that beta decay, like alpha decay, was of nuclear origin. As a rsult, Soddy considered van den Brock’s hypothesis, that successive places in the periodic table correspond to unit differences in the net intra-atomic charge (see Figure 1) “practically proved so far as the ... end of the sequence, from thallium to uranium, concerned.”19

By early 1914 Moseley,20 using physical methods, had completed his independent extension of this verification throughout the entire periodic table. During the period 1914–1919, in the chair of chemistry at Aberdeen. Soddy, in addition to his war work, examined two predictions of the displacement law. It was commonly accepted that lead was the end product only of the uranium series, and Soddy had predicted by 1913 that a heavier isotope of lead from thorium must also exist. Separate determinations were undertaken in 1914 on lead from Ceylon thorite by Soddy and on lead from uranium ores by T. W. Richards and O. Hönigschmid, thereby confirming the prediction that common lead was indeed a mixture of isotopes.21 Soddy suggested that the parent of actinium might be an alpha-decaying member of Mendeleev’s missing eka-tantalum. An exclusively beta-emitting homologue of tantalum found by Fajans and O. Göhring in 1913 and called “brevium” [UrX2], however, caused Soddy to begin to investigate the other alternative. But after proving that the parent of actinium could not be a beta-decay product of radium, he reexamined the first alternative with Cranston. In 1918 they found, isotopic with UrX2, the direct parent of actinium, produced through the rare UrY branch, which was found in 1911 by G. Antonoff and later linked to uranium 235. Protactinium, element 91, was simultaneously and independently found by Hahn and Meitner.

Soddy was called in 1919 to a chair of chemistry at Oxford. During his seventeen-year tenure, he failed to establish the expected school of radio-chemistry, devoting himself rather to the improvement of chemistry teaching and to the modernization of the laboratories.22. He also continued to treat radioactive minerals for their constituents. After the disturbing death of his wife. Soddy retired early. He went exploring for monazite sand, and patented his 1923 process for thorium extraction in 1940. He then turned his attention to mathematics. Looking beyond to the significance of science, Soddy. who had once confidently spoken of the potential peaceful benefits for society given the key to “unlock this great store of energy bound up in the structure of the element”23 and, by controlling itt “virtually provide anyone who wanted it with a private sun of his own,”24 was profoundly concerned by subsequent developments. He zealously endeavored25 to awaken the conscience of the scientific community to the social relevance of their own research. Soddy urged that “universities and learned societies should no longer evade their

responsibilities and hide under the guise of false humility as the hired servants of the world their work has made possible, but do that for which they are supported in cultured release from routine occupations, and speak the truth though the heavens fall.”26 He was largely unheeded, however, and he judged at the end that the blame for the plight of civilization “must rest on scientific men, equally with others, for being incapable of accepting the responsibility for the profound social upheavals which their own work primarily has brought about in human relationships.”27


1. Rutherford letter. 15 June 1914. Cf Howorth. Pioneer Research, 192. The original is in Bodleian Library, Soddy-Howorth Collection, 75, 95, courtesy Soddy trustees.

2. Soddy, Memoris, I , 274.

3. Fleck, “Soddy,” 210, courtesy the Royal Society.

4. Soddy, “Social Relations of Science.” in Nature, 141 (1938), 784–785.

5. A comprehensive statement of his general view regarding the monetary system preventing modern Western civilization from distributing its scientific and technological abundance by peaceful means appears in an address, February 1950. partially republished in the 24-page Commemoration to Professor Frederick Soddy (London, 1958).

6. Soddy, “Multiple Atomic Disintegration: A Suggestion in Radioactive Theory,” in Philosophical Magazine, 18 (1909). 739–744; this was developed in “Multiple Disintegration,” in Annual Report, 9 (1912), 311–316.

7. Referring to his joint paper with Royds. Philosophical Magazine, 17 (1909), 281, Rutherford further noted in his letter of 14 Feb. 1909 to Elster and Geitel that “you will have seen that the α particle has at last been proved to be helium.” Darmstaeidter Collection, G 1, 1896 (26), courtesy Staatsbibliothek, Preussischer Kulturbesitz.

8. Soddy, “Radioactivity,” in Annual Report, 7 (1910), 286.Strikingly similar views regarding mixtures of similar elements of different atomic weight were expressed by D. Strömholm and T. Svedberg in Zeitschrift für Anorganische chemie, 63 (1909), 206.

9. Fleck, “Soddy,” 208. The rare earths had given ample evidence of chemical “inseparability” without identity.

10. Soddy, “Intra-atomic Charge,” in Nature, 92 (4 Dec. 1913), 400. “The same algebraic sum of the positive and negative charges in the nucleus, when the arithmetic sum is different, gives what I call ‘isotopes’ ... because they occupy the same [iso] place [topos] in the periodic table” (see diagram). Perhaps the first use of “isotope” for the position of elements was W. Preyer, Das Genetische System der chemischen Elemente (Berlin, 1893), The stimulus for Soddy’s term arose when he “got tired of writing ‘elements chemically identical and non-separable by chemical methods’ and coined the name isotope ....” as he said in “Contribution to a Discussion on Isotopes,” in Proceedings of the Royal Society, 99 (1921), 98.

11. Soddy, “Radioactivity.” in Annual Report,16 (1913). 265.

12. Aston, Isotopes, 37, 42.

13. Soddy, “The Chemistry of Mesothoriurm,” in Transactions of the Chemical Society, 99 (1911), 82; cf. n. 8.

14. Soddy, The Chemistry of the Radioelements (1911),29.For a remarkable partial anticipation of isotopes and the displacement law, see A. T. Cameron. Radiochemistry (London, 1910), 141.

15. Soddy letter to F. O. Giesel, ca, 1913/14 in Giesel Archives, courtesy Chininfabrik, Buchler & Co., Brunswick. The generalization of A. S. Russell had not only assumed a discontinuous series,Chemical News, 107 (31 Jan. 1913), 49, but also questioned the chemical identity notion of Soddy; cf. Russell letter to Rutherford, 14 Sept. 1912, Cambridge Univ. Lib., Add. MSS 7653/R106. Russell “knew of Fleck’s results,” and “through him they got known to Hevesy and Fajans”; cf. Report of the British Association for the Advancement of Science (1913), 446; and the Soddy letter to Howorth, 29 Jan. 1953, Bodleian Lib., Soddy Collection, Alton 29, item no. Trenn S-6.

16. K.Fajans, Radioaktivität und die neueste Entwickelung der Lehre von den chemischen Elementen (Brunswick, 1919), 35.

17. Fajans’ letter to Rutherford, 10 April 1913, Cambridge Univ. Lib. Add. MSS 7653/F5.

18. Soddy’s distinction between chemical change and radiochange was originally based upon the disintegration theory, “Radioactive Change,” in Philosophical Magazine, 5 (1903), 576. With the development of the nuclear atom, however, it became possible to clarify this distinction by defining the actual locus of the radio-changes. Bohr expressed this clarification in his letter to Hevesy, 7 Feb. 1913, L. Rosenfeld, “Introduction” to On the Constitution of Atoms and Molecules (Copenhagen, 1963), xxxii.

19. Soddy. “Intra-atomic Charge,” 400.

20. H. G. J. Moseley, in Nature, 92 (1914), 554. “My work was undertaken for the express purpose of testing [van den] Broek’s hypothesis ... [and] certainly confirms the hypothesis.”

21. “Soddy’s prediction concerning the atomic weights of leads from uranium and thorium minerals had been triumphantly vindicated by some of his most severe critics.” F. W. Aston, “The Story of Isotopes,” in British Association Report (1935), Presidential Address to Section A, p. 26. The concurrent investigations comparing uranium lead with ordinary lead could neither confirm nor deny the possibility of thorium lead.

22. Brewer, “Chemistry at Oxford,” 185.

23. Soddy, “The Internal Energy of Elements,” inJournal of the Proceedings of the Institution of Electrical Engineers, Glasgow, 37 (1906), 7. An earlier statement on the latent internal energy of the atom is Soddy, “The Disintegration Theory of Radioactivity,” in Times Literary Supplement (26 June 1903), 201.

24. Soddy, “Advances in the Study of Radio-active Bodies,” two lectures to the Royal Institution on 15 May and 18 May 1915, as recorded in The Royal Institution Friday Evening Lectures 1907–1918 (privately bound at the Royal Institution London, n.d.). The original MS is in the Bodleian Library. Soddy-Howorth Collection, 58. The quotation is from this MS, page II , 9. The lectures are apparently unpublished but are reviewed in Engineering, 99 (1915), 604.

25. Shortly after Soddy’s retirement, Joseph Needham pointed out the importance of such efforts, “Social Relations of Science,” in Nature, 141 (1938), 734.

26. Soddy, Frustration in Science, Foreword.

27. Soddy, Typescript-A, 1953, concluding statement, Bodleian Library, Soddy-Howorth Collection 4.


A nearly complete list of Soddy’s main scientific papers, books, lectures, and other contributions is given by Alexander Fleck, “Frederick Soddy,” in Biographical Memoirs of Fellows of the Royal Society, 3 (1957), 203–216. For comparisons and additions, including his contributions on economics and on science and society, see Muriel Howorth, Pioneer Research on the Atom (London, 1958), 281–286. This unusual account is subtitled Rutherford and Soddy in a Glorious Chapter of Science, and further subtitled The Life Story of Frederick Soddy. In spite of the author’s uncritical attempt to glorify Soddy, this remarkable reference source is the fruit of great effort to preserve the existing documents of Soddy. Soddy gave all his papers to Muriel Howorth of Eastbourne, and his will contained the provision: “I give to Muriel Howorth also the copyright of all my published works,” cf. Pioneer Research, p. 286. The Soddy-Howorth Collection was deposited in the Bodleian Library and a partial reference key thereto is appended to Pioneer Research, pp. 333–339. In 1974 J. Alton of the Contemporary Scientific Archives Centre, Oxford, deposited in the Bodleian a 29-page systematic catalogue of the Soddy Collection incorporating the Howorth portion. This collection must be directly consulted for precision in both quotations and other references. Richard Lucas, Bibliographie der radioaktiven Stoffe (Leipzig, 1908), 72–73, provides a useful list of Soddy’s early works. Consultation of the British Museum General Catalogue of Printed Books, 1964, amplifies the list of works of Soddy. In addition to the scientific contributions collectively listed in Fleck and Howorth, the following should be noted: “The First Quarter-Century of Radioactivity,” in Isotopy (Westminster, 1954), 1–25. See the obituaries of “Rutherford,” in Nature (30 October 1937); “Ramsay,” ibid. (10 August 1916); and of H. Becquerel, “The Founder of Radioactivity,” in lon:A Journal of Electronics, Atomistics, Ionology, Radioactivity and Raumchemistry, 1 (1908), 2–4. Soddy was joint editor of this short-lived serial, Ion. In this same issue, Soddy completed his series of investigations concerning whether the alpha particle was charged before, during, or after expulsion. Soddy’s abstracts of the papers by Russell. Fajans, and Soddy concerning the displacement law are also of interest; see Abstracts of Chemical Papers Journal of the Chemical Society London, pt. 2 (1913), 274–278. Soddy’s classic call for scientific responsibility appears as the foreword to frustration in Science (London, 1935).

Soddy’s nine joint papers with Rutherford (1902–1903) are reproduced in Collected Papers of Lord Rutherford of Nelson, Sir James Chadwick, ed., I (London, 1962). Soddy contributed a series of original reports on “Radioactivity” for the Annual Reports on the Progress of Chemistry (London, 1904–1920). These articles contain much otherwise unpublished work on isotopes, as well as a running account of the history of radioactivity. These articles have been published in facsimile and edited with commentary by T. J. Trenn, in Radioactivity and Atomic Theory (London. 1975), The diagram “Radio-Elements and Periodic Law” first appeared as a supplement to Soddy’s paper “The Radio-elements and the Periodic Law,” in Chemical News, 107 (28 Feb. 1913), 97–99. Essentially the same diagram appeared Jahrbuch der Radioaktivität und Elektronik, 10 , no. 2 (1913), 193. The actinium series was separated and minor additions were included in the version drafted July 1913 for the British Association Report (1913), 446, and here reproduced; it also appeared in the Annual Report, 10 (1913), 264.

Soddy’s most important books are Radio-Activity: an Elementary Treatise From the Standpoint of the Disintegration Theory (London-Leipzig, 1904), based upon a series of lectures at the University of London from Oct. 1903 to Feb. 1904, c The Electrician, 52 (1903), 7 et. seq.; The Interpretation of Radium (London, 1909; 4th ed., 1920), translated into several languages). In the series edited by Alexander Findlay, Monographs on Inorganic and Physical Chemistry, Soddy contributed The Chemistry of the Radio-Elements, pt. I (London. 1911: Leipzig, 1912); pt. II (1914), containing “Radioelements and the periodic Law” and pt. I, 2nd. ed. (1915). See also The Interpretation of the Atom (London, 1932).

Soddy’s most important lectures were The Wilde Lecture VIII, “The Evolution of Matter as Revealed by the Radioactive Elements,” 16 March 1904, in Memoirs and Proceedings of the Manchester Literary and Philosophical Society, 48 (1904; Leipzig, 1904); The Nobel Lecture, 12 Dec. 1922, “The Origin of the Conception of Isotopes,” in Les Prix Nobel en1921–1922 (Stockholm, 1923).

Information concerning the life and work of Soddy can be obtained from Pioneer Research. Howorth also edited the Memoirs of Soddy, as Atomic Transmutation, Memoirs of Professor Frederick Soddy. vol. I (London, 1953), subtitled The Greatest Discovery Ever Made. Volume one deals with the period until 1904. There were no further volumes. There are numerous sketches of Soddy’s life and work. Alexander Fleck, in Nature, 178 (1956), 893, is an interesting personal account. Fleck also contributed the note for the Dictionary of National Biography (l951–l960), 904. Alexander S. Russell, “F. Soddy, Interpreter of Atomic Structure,” in Science, 124 (1956), provides insights into Soddy the man.. Russell published further on Soddy, in Chemistry and Industry, no. 47 (1956), 1420–1421, and in Eduard Farber, ed., Great Chemists (New York, 1961), 1463–1468. Perhaps the best account is F. Paneth, “A Tribute to Frederick Soddy,” in Nature, 180 (1957), 1085–1087; repr. in the Paneth Collection, H. Dingle, ed., Chemistry and Beyond (London, 1964), 85–89, A more recent sympathetic account is that of A. Kent, “Frederick Soddy,” in Proceedings of the Chemical Society (November 1963), 327–330. Besides his brief editorial “Frederick Soddy and the Concept of Isotopes,” in Endeavour, 23 (1964)54, T. I. Williams wrote the article on Soddy for his Biographical Dictionary of Scientists (London, 1969). The account of I. Asimov, Biographical Encyclopedia of Science and Technology (New York, 1964), no. 398, is subject to the limitations imposed by this effort. An extremely concise and accurate summary is included in W. A. Tilden and S. Glasstone, Chemical Discovery and Invention in the Twentieth Century (London, 1936), 140. There is a supplementary account in Eduard Farber, Nobel Prize Winners in Chemistry 1901–1961 (London, 1963), 81–85. It is of interest to compare the biographical account in Nobel Lectures in Chemistry (Amsterdam, 1966), 400–401, with the original in Les Prix Nobel en 1921–1922 (Stockholm, 1923), 128–129. See also the account in H. H. Stephenson, Who’s who in Science (London, 1914), 535, and Journal of Chemical Education, 8 (1931), 1245–1246.

Relevant sketches of Soddy’s work are to be found in F. W. Aston, Isotopes, 2nd ed., 1924. His work on lead isotopes, pp. 17–19, is particularly valuable. See A. Kent and J. A. Cranston, “The Soddy Box,” in Chemistry and Industry (1960), 1206, 1411, which describes Soddy’s original 1910 preparation, a deliberate mixture of radium and mesothorium, which led him to the comcept of the isotope. In Gleditsch, “Contribution to the Study of Isotopes,” Norske Videnskaps-Akademi I. Mat-Natur. Klasse no. 3 (Oslo, 1925), E. Gleditsch notes, p. 7, that “The theory of isotopes put forward… by Soddy in the years 1911–1914 has proved to be fully in accord with our present views on atomic structure.” See also Fleck, “Early Work in the Radioactive Elements,” in Proceedings of the Chemical Society” (1963), 330. In this same issue, J. A. Cranston contributed “The Group Displacement Law,” pp. 330–333 and an even more detailed documentation in the following issue (1964), 104–107. Soddy’s work with Rutherford is considered by A. S. Eve, Rutherford (Cambridge, 1939); N. Feather, Lord Rutherford (London, 1940); A. Romer, The Restless Atom (New York, 1960); Howorth, Pioneer Research; and T. J. Trenn, “Rutherford and Soddy: From a Search for Radioactive Constituents to the Disintegration Theory of Radioactivity,” in Rete, 1 (1971), 51–70. M. W. Travers, A Life of Sir William Ramsay (London, 1956), ch. 14, pp. 210–221, deals with his work with Ramsay. At the request of Travers, Soddy contributed a portion of this account. The original transcript is in Soddy-Howorth 4.

In addition to F. M. Brewer, “The Place of Chemistry at Oxford,” in Proceedings of the Chemical society (July 1957), 185, Soddy’s work at Oxford is considered by Sir Harold Hartley, “The Old Chemical Department,” in Journal of the Royal Institute of Chemistry(1955). 126,.J. A.Cranston’s“The Discovery of Isotopes by Soddy and his School in Glasgow,” in Isotopy( 1954). 26–36 and “Concept of Isotope.” in Journal of the Royall Institute of Chemistry. 18 (1964). 38. provide important historical and scientific distinctions in the use of the term “isotope.”.

A. Romer, ed., The Discovery of Radioactivity and Transmutation, Classics of Science, II (New York, 1964), provides not only some of the papers of Soddy in collaboration both with Rutherford and with Ramsay but also valuable comments on this pre-1904 work. Soddy’s hypothesis concerning an isotope of lead as the final product of the thorium series is dealt with in S. I. Levy, The Rare Earths (London. 1915). 107–108.

For a partial account of Soddy’s work on isotopes, emphasizing the contributions of Fajans and Richards, see O. U. Anders, “The Place of Isotopes in the Periodic Table: the 50th Anniversary of the Fajans-Soddy Displacement Laws,” in Journal of Chemical Education41 (1964), 522–525. Additional information about Soddy as others saw him is in L. Badash, ed., Rutherford and Boltwood: Letters on Radioactivity (New Haven, 1969), which exposes Soddy’s research on the parent of radium. Soddy as a public figure and social rebel, who ushered in the atomic age, is epitomized in C. Beaton K. and Tynan, Persona Grata (London, 1953), 87. Besides the Soddy-Howorth Collection, extensive correspondence exists also at the Cambridge Univ. Library, Add. MSS 7653/S. There is also correspondence with W. H. Bragg the Royal Institution, with J. Larmor courtesy the Royal Society, and with O. Lodge at University College London. The Soddy Memorial at Glasgow was reported in “Unveiling of the Soddy Memorial.” in Chemistry and Industry (8 Nov. 1958). 1462–1464. There is one collection of Soddy’s apparatus and equipment at the Chemistry Department of the University of Glasgow and another at the Inorganic Chemistry Laboratory of the University of Oxford.

Thaddeus J. Trenn

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Frederick Soddy

Frederick Soddy

The English chemist Frederick Soddy (1877-1956) shared in the discoveries of atomic disintegration and of helium production during radioactive decay and introduced the term "isotope" to nuclear science.

Frederick Soddy was born at Eastbourne, Sussex, on Sept. 2, 1877. He studied at Eastbourne College; University College, Aberystwyth; and Merton College, Oxford, where in 1898 he received his degree in chemistry.

Radioactivity Studies at Montreal

Having accepted a demonstratorship in chemistry at McGill University, Montreal, Soddy found himself increasingly attracted by the work being done by Ernest Rutherford, then research professor of physics at the university. He joined Rutherford's team and brought to it his valuable experience as a chemist.

In a study of the radioactivity of thorium, Rutherford and Soddy added ammonia to a solution of a thorium salt, so precipitating out thorium hydroxide. When the insoluble material had been filtered off, the remaining solution still showed radioactivity. They established that this was due to a highly radioactive substance which they called thorium-X. Detailed measurements were made of the radioactivity of solution and precipitate over a number of weeks, and it became clear that different chemical species were involved in the process of radioactive decay over the period studied.

Further evidence for a strangely new kind of disintegration came from Rutherford's and Soddy's examination of the behavior of uranium, which when pure, emitted alpha particles only. The beta emission often encountered must therefore come from some other substance. Rutherford had already noted a gaseous emanation from thorium; now, with Soddy, he suggested that it belonged to the inert gas family. Also, they removed all doubts about the existence of a similar emanation from radium by condensing it with liquid air.

Soddy, who had long been interested in the historical problem of alchemy, now used the alchemical term "transmutation" to describe the changes that are accompanied by radioactive emission. Rutherford adopted the concept, and in 1903 they announced the general theory of radioactive disintegration. They proposed that radioactivity was an atomic phenomenon and that radiation was an accompaniment of chemical transmutations of the atoms themselves. This theory, though often bearing Rutherford's name alone, was in fact a product of the joint activity of Rutherford and Soddy.

Helium Studies at London

In 1903 Soddy left Montreal for London, drawn by the reputation of Sir William Ramsay at University College. Soddy was anxious to study further the gases associated with radioactive materials. Ramsay's laboratory, internationally acclaimed for the addition of the inert gases to the periodic table, was almost the only place where minute quantities of rare gases could be successfully examined.

Ramsay had recently acquired a small amount of radium bromide, and he and Soddy examined the gaseous emanations which were pumped off. After removal of oxygen and other common gases, the residue was examined spectroscopically. It was found to give the same spectrum as helium. When the gas was cooled by liquid air to remove the helium, the residue, as expected, gave no helium spectrum; but after a few days the helium line reappeared. Clearly helium had formed as a product of radioactive decay. Soddy concluded that the helium originated with the alpha particles, which were thus helium nuclei—a view later confirmed by Rutherford. Ramsay and Soddy showed that the other gaseous emanations were true inert gases.

Defining the Isotope at Glasgow

In 1904 Soddy moved to the University of Glasgow to take up a special appointment as lecturer in physical chemistry (including radiochemistry). During his first few years he made steady progress in purifying radioactive materials. In 1908 he married Winifred Beilby, only daughter of George Beilby of the Cassell Gold Extracting Company, which provided financial support for a research program in which Soddy was engaged involving methods of extraction for possible substitutes for radium. This project yielded few results of importance.

In 1910 Soddy turned his attention to the short-lived radioelements, collaborating with Alexander Fleck. They decided to establish the chemical characteristics of every known member of the disintegration series. They showed that in several cases a number of intermediates were chemically identical and inseparable from one another, yet underwent radioactive decay in quite different ways. Thus identical chemical properties were shown by radium-B, thorium-B, actinium-B, and lead.

Soddy's first generalization on these mysteries came in his rule that loss of an alpha particle from an atom with an even number in the periodic table produces an atom with the next lower even number. In subsequent changes, however, when alpha emission does not take place, a reversion to the original "family" may occur, and the products will be chemically inseparable from the starting material, even though the atomic weights vary. Complementary to this alpha-particle rule is the one that in beta emissions an atom moves up one place in the periodic table. In 1913 Soddy combined the alpha and beta rules into the group displacement law: one alpha emission causes a shift two places back in the periodic table, and one beta emission causes a shift one place further on. Hence a sequence of alpha-beta-beta emissions would mean a return to the original place in the table.

The underlying concept, that more than one kind of atom might be assignable to the same chemical "space," was daring and revolutionary. In December 1913 Soddy brought matters to a head by writing a letter to Nature in which he proposed that such chemically inseparable species should be termed "isotopes." In modern parlance, they differ from each other in mass but not in overall nuclear charge. The group displacement law and the related concept of isotopy were soon confirmed.

In 1914 Soddy became professor of chemistry at Aberdeen. His fortunes here were immediately and drastically affected by the war. He was able to complete some of the work begun in Glasgow, but his radiochemical researches were brought to a premature end by the special wartime demands made upon his laboratories.

Oxford and Retirement

With the ending of the war the future held great promise for radiochemical studies in Britain. In 1919 Soddy was appointed Lee's professor of inorganic and physical chemistry at the University of Oxford. Two years later he received the Nobel Prize in chemistry for his contributions to radio-chemistry and, particularly, to the concept of isotopes.

It was widely hoped that, under Soddy's leadership, a British school of radiochemistry would emerge at Oxford that would complement the work of the atomic physicists at the Cavendish Laboratory in Cambridge. Unfortunately this was not to be, for his output of original work in science was negligible. In 1936 he resigned his chair. The death of his wife no doubt contributed to his discontent, but this cannot explain the full measure of his apparent disenchantment with experimental work.

Soddy was an extremely talented writer, and to some extent his literary gifts may have interfered with his laboratory research. His first book, Radioactivity, appeared in 1904. For many years, beginning in 1904, he contributed articles on radioactivity to the Annual Reports of the Chemical Society. The Interpretation of Radium (1909) was a popular treatise deriving much from his Glasgow lectures. The Chemistry of the Radioelements (1910) was a concise and reliable summary of the contemporary position. Later works included The Interpretation of the Atom (1932) and The Story of Atomic Energy (1947). He also wrote several books on economic theory. He died on Sept. 21, 1956, in Brighton.

Further Reading

Muriel Howarth, Pioneer Research on the Atom (1958), contains a biography of Soddy. The Royal Society of London, Biographical Memoirs of Fellows of the Royal Society, vol. 3 (1957), has a biography of Soddy by Sir Alexander Fleck. Additional material is in Henry A. Boorse and Lloyd Motz, eds., The World of the Atom (2 vols., 1966).

Additional Sources

Frederick Soddy (1877-1956): early pioneer in radiochemistry, Dordrecht; Boston: D. Reidel Pub. Co.; Hingham, MA, U.S.A.: Sold and distributed in the U.S.A. and Canada by Kluwer Academic Publishers, 1986.

Merricks, Linda, The world made new: Frederick Soddy, science, politics, and environment, New York: Oxford University Press, 1996. □

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Soddy, Frederick

Soddy, Frederick


Frederick Soddy, the youngest of seven sons of a London corn merchant, was born on September 2, 1877, in Eastbourne, England. Raised by his half-sister, this precocious scientist attended Eastbourne College (18921894) and the University College of Wales, Aberystwyth (1895). In 1895 he won a scholarship to Merton College, Oxford University, from which he graduated with the highest honors in chemistry (1898).

After two years of research at Oxford, Soddy served as a demonstrator (laboratory instructor) at McGill University in Montreal, Canada (19001902), where he worked with Ernest Rutherford, studying the gaseous emanation of radium and showing that radioactivity involved the disintegration of radioactive atoms to form new elements. He called the process "transmutation," a term that he borrowed from alchemy .

The two proved the existence of two radioactive decay series: one starting with uranium and the other with thorium. The final product of both series was lead. They predicted that helium should be the decay product of radium, and they were the first to calculate the tremendous amount of energy that could be evolved during radioactive reactions.

Soddy then worked with William Ramsay at University College, London (19031904), where they used spectroscopy to show that helium was formed during the radioactive decay of radium and that it was also evolved in the decay of radium emanation. From 1904 to 1914 he served as a lecturer in physical chemistry and radioactivity at the University of Glasgow.

At Glasgow, Soddy posited his "group displacement law," which stated that the emission of an α -particle (a doubly charged particle consisting of two protons and two neutrons, identical to the helium nucleus, He2+) from a radioactive element causes that element to move back two places in the Periodic Table. In a short letter to the editor of Nature, published on December 4, 1913, he first proposed the term isotope to designate chemically identical elements with different atomic weights (in modern terms, elements with the same atomic numbers but different mass numbers). Isotopes occupy the same place in the Periodic Table.

Soddy wrote and spoke about the practical applications of radioactivity and envisioned nuclear energy as the basis for an advanced civilization and as a solution to the increasing depletion of natural resources. His book The Interpretation of Radium (1914) inspired H. G. Wells to write his science fiction novel The World Set Free (published the same year).

After he left Glasgow, Soddy abandoned his work on radioactivity and no longer followed recent advancements in the field. He developed an interest in financial, economic, social, and political theories, which found no general acceptance, as well as unusual mechanical and mathematical problems.

In 1914 Soddy assumed the chair of chemistry at Aberdeen University, Scotland, but his teaching and research were largely interrupted by World War I. In 1919 he was appointed to the Lee Chair of Chemistry at Oxford University, a post he held until his retirement in 1937. In 1921 Soddy received the Nobel Prize in chemistry "for his contributions to our knowledge of the chemistry of radioactive substances, and his investigations into the origin and nature of isotopes." He died in Brighton, England, on September 22, 1956.

see also Ramsay, William; Rutherford, Ernest.

George B. Kauffman


Hunter, Norman W., and Roach, Rachel (1993). "Frederick Soddy 18771956." In Nobel Laureates in Chemistry 19011992, ed. Laylin K. James, pp. 134139. Washington, DC: American Chemical Society; Chemical Heritage Foundation.

Kauffman, George B. (1982). "The Atomic Weight of Lead of Radioactive Origin: A Confirmation of the Concept of Isotopy and the Group Displacement Laws." Journal of Chemical Education 59(1): 38; 59(1): 119123.

Kauffman, George B., ed. (1986). Frederick Soddy (18771956): Early Pioneer in Radiochemistry. Boston: D. Reidel.

Russell, Alexander S. (1956). "Frederick Soddy 18771956." Chemistry & Industry 47: 1,4201,421. Reprinted in Great Chemists, ed. Eduard Farber, pp. 1,4641,468. (1961). New York: Wiley-Interscience.

Soddy, Frederick (1966). "The Origins of the Conceptions of Isotopes, Nobel Lecture, December 12, 1922." In Nobel Lectures Including Presentation Speeches and Laureates' Biographies: Chemistry 19011921. New York: Elsevier, pp. 367401. Also available from <>.

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Soddy, Frederick

Frederick Soddy (sŏd´ē), 1877–1956, English chemist. He worked under Lord Rutherford at McGill Univ. and with Sir William Ramsay at the Univ. of London. After serving (1910–14) as lecturer in physical chemistry and radioactivity at the Univ. of Glasgow, he was professor of chemistry at the Univ. of Aberdeen (1914–19) and at Oxford (1919–36). He was especially noted for his research in radioactivity. With others he discovered a relationship between radioactive elements and the parent compound, which led to his theory of isotopes; for this work he won the 1921 Nobel Prize in Chemistry. His scientific books have become classics and include The Interpretation of Radium (1909, rev. ed. 1922), Matter and Energy (1912), The Chemistry of the Radio-Elements (2 parts, 1911–14), and Atomic Transmutation (1953). An advocate of technocracy and of the social credit movement, he wrote several books setting forth his political and economic views.

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Soddy, Frederick

Soddy, Frederick (1877–1956) English chemist who received the 1921 Nobel Prize in chemistry for his studies of radioactive isotopes. In 1920, Soddy revealed the value of isotopes in computing geological age. With Ernest Rutherford, he worked out an explanation of radioactive decay and later, with William Ramsay, found helium to be a product of uranium decay.

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