The Early History of Radioactivity (1896-1904) Thesis presented for the degree of Doctor of Philosophy in the Field of History of Science by Stephen Brian Sinclair Department of History of Science and Technology Imperial College of Science and Technology University of London May 1976 2 ABSTRACT Both the beginning and end of this history are ostensibly well defined. Becquerel's quiet discovery of uranium rays came to fruition in the appearance of the first standard textbooks on radioactivity, with their claims for an independent subject area. One may see in the intervening period the progressive construction of a new bridge between physics and chemistry founded on a coherent theory of atomic transmutation and disintegration. My examination of the scene from the viewpoints of several interested parties reveals an alternative picture comprising complex linked series of discoveries, experiments and hypotheses of various levels. At the moving boundaries of research the results and conclusions of individuals were always subject to reinterpretation in their adoption by others. This study thus proceeds in the light of three main considerations. These are, firstly, parallel investigations in radioactivity by different workers; secondly, contemporary related areas of physical science such as X-rays, cathode rays, corpuscular theory; and thirdly, the relevant concepts developed earlier, during the nineteenth century. The introductory chapter concentrates upon the last of these, considering some long-standing hopes and unanswered questions concerning, for example, the unification of matter, ether, and electricity, and the relations between the chemical elements. This forms an essential part of the background to radioactivity. Chapter two describes the opening of the radiochemical field by the Curies, following Becquerel's original discovery, and discusses the blending of these results with Rutherford's earliest radiation studies. The third chapter deals with a confused phase where new observations 3 outran theory as 'emanations', 'induced' activities, spontaneous cathode-ray emissions, and dubious radiochemical claims combined with the ever-growing energy problem. The fourth and fifth chapters trace the emergence of rival theories, and the singular success of one of these at the expense of all others. 4 ACKNOWLEDGMENTS I wish to thank for their assistance those who made manuscript materials available to me at the following institutions: Cambridge University Library, Bibliotheque Nationale, Academie des Sciences, Royal Institution of Great Britain, Wellcome Institute for the History of Medicine Library, Library of University College London, Library of the Royal Society, Bodleian Library, Science Museum Library, Imperial College Archives. To my research supervisor Dr. M.B. Hall of the Department of History of Science and Technology, Imperial College, I am greatly indebted for her patient advice throughout the project and for her careful reading of this thesis during its construction. TABLE OF CONTENTS ABSTRACT 2 ACKNOWLEDGEMENTS 4 CHAPTER 1. NINETEENTH-CENTURY THREADS 8 1. Introduction 8 Scientific revolution - summary of threads. 2. Chemical atomic theories and the unity and complex ty of the chemical elements 12 Dalton's theory - evolution and compound nature of elements - Crookes - Stokes - Lockyer - J.J.Thomson. 3. Physical theories of matter, electricity, ether 24 Maxwell - various ethers - Larmor - Lorentz - Zeeman - Mme.Curie, Rutherford - Hertzian molecule. 4. Chemical physics. Physical chemistry 32 Hertzian atom - Stoney's electron theory - electrochemistry - vortex atom - J.J.Thomson - electricity and gases - corpuscular atom. CHAPTER 2. THE DISCOVERY OF URANIUM RAYS AND RADIOACTIVITY 48 1. Becquerel's discovery of uranium rays (1896-7) 48 X-rays and phosphorescence.- Becquerel and uranium rays - nature of the rays - S.P.Thompson - other radiations - vapours and W.J.Russell's photographic work - electrical studies. 2. Rutherford, and the Cavendish Laboratory (1894-8) 70 Hertzian radiation and magnetism - X-rays and conductivity of gases - ionic theory - ultraviolet radiation - uranium rays. 3. Pierre Curie, Marie Curie and the new radioactive elements (1890.17)-- 92 P.Curie's researches - Marie Curie - thorium rays - G.C.Schmidt - polonium - radium - atomic property - energy source, speculations. 4. Theories and trends (1896-9) 110 Source of the energy - interest in uranium rays - development of theories - atomic change. 6 CHAPTER 3. EMANATIONS AND RADIATIONS 119 1. The ma netic deflection of the Becquerel rays 1 9-1900) 119 The rays from active substances and their magnetic deflection - magnetism and radio- activity - Becquerel's 'material rays'. 2. The discovery of induced radioactivity (1899) 129 The Curies' discovery, 'la radioactivite induite' - Rutherford's idea of a thorium emanation - properties of the emanation - the production of a radioactive deposit. 3. The source of radioactivity (1900) 147 The effect of temperature change and its implications - phosphorescence, Behrendsen, and the views of Becquerel - Marie Curie's speculations on atomic change and disintegration - Rutherford and the energy of radioactivity. 4. Emanations and the X-substances (1900-1) 162 Fitzgerald, and transmutations - A.Debierne and actinium - induced radioactivity: Giesel, Hofmann, and radiolead; P.Villard - Crookes and UrX - the Curies' views - E.Dorn and an emanation from radium - Rutherford's problems with the emanations - atmospheric emanation of Elster and Geitel. CHAPTER 4. DISINTEGRATION, INDUCTION, TRANSFORMATION 179 1. The emergence of induction and disintegration gorfes (1901-1.) 179 Ionic and emanation hypotheses of Elster and Geitel - comparison of theories - induced radioactivity; the function of the gaseous medium - radioactive water; the induction theory of Curie and Debierne - Becquerel, uranium and auto-induction - Curies' criticism - Crookes and ultra-atomic diffusion - Martin and total disintegration - J.Stark and the genesis of atoms . 2. A quantitative theory of atomic transmutation T1902) 196 Introduction - F.Soddy - the first joint publication: an inert gas from thorium, a possible transmutation; ThX as the source of the emanation - Rutherford and the transmission of excited radioactivity - interpretations of Becquerel's views - the second publication: thorium and ThX, transmutation quantitatively observed - the new accompaniment version of the disintegration theory, and the question of induction. 7 CHAPTER 5. RECEPTIONS, GENERALISATIONS, SPECULATIONS 226 1. Reception of the disintegration theory (1902-3) 226 Introduction - changing views of the Caries; the heat from radium - F.Giesel - J.J.Thomson: wind, water, and atomic disintegration - Crookes and the mysteries of radium; a wider public - creation of helium; the Curies converted - the summit of fame - physicists and chemists: a campaign well fought. 2. The mechanism of radioactivity (1903-4) 252 Speculations of physical chemists: ether, energy, electrons - Soddy and the randomness of disintegration - physical models for radioactivity - Lodge's radiation-loss hypothesis - Kelvin's atomic theories - Nagaoka's saturnian atom - Thomson's corpuscular atom. 3. Conclusion 271 Rutherford and the succession of changes - cosmical, universal, and Proutian radioactivity. NOTES FOR CHAPTERS 1 to 5 281 BIBLIOGRAPHY 331 Ri3 RE .f% 14-nonis 361e 8 CHAPTER 1 NINETEENTH-CENTURY THREADS 1. Introduction The discovery of X-rays by ROntgen in 1895, which led directly to Becquerel's discovery of uranium rays, has been hailed as marking a watershed in physics, the beginning of a revolution. This interpretation generally invokes the further statement that from 1880 to the turn of the century physical science had attained a satisfactory state with few internal problems.'The latter idea, with its implication of some form of stagnation in research, seems the more dubious of the two. The words of Maxwell's 'Introductory Lecture on Experimental Physics' of 1871 have been used to support this view: the opinion seems to have got abroad, that in a few years all the great physical constants will have been approximately estimated, and that the only occupation which will then be left to men of science will be to carry on these measurements to another place of decimals.2 That this was not 'really the state of things to which we are approaching' is shown by his own continuation: But we have no right to think thus of the unsearchable riches of creation, or of the untried fertility of those fresh minds into which these riches will continue to be poured...3 And although the great chemist Marcelin Berthelot in introducing his book, Les Origines de L'Alchimie, of 1885, wrote that the worm was then 'without mystery',4 scientists in other areas took quite the opposite view. Oliver Lodge concluding his book Modern Views of Electricity, of 1889,. wrote: 'Conclusion' is an absurd word to write at the present time, when the whole subject is astir with life, and when every month seems to bring out some fresh aspect...5 And we will leave Lodge with a resounding word on this particular point, in his lecture on 'The Discharge of a 9 Leyden Jar' at the Royal Institution, in the same year; The present is an epoch of astounding activity in physical science. Progress is a thing of months and weeks, almost of days. The long line of isolated ripples of past discovery seem blending into a mighty wave, on the crest of which one begins to discern some oncoming magnificent generalisation. The suspense is becoming feverish,