Soddy

Perrin, J. (1909) Annales de Chimie et de Physique 18, 1. English translation by F. Soddy, Brownian Movement and Molecular Reality (Taylor Francis, London) 1910. 

Element 86, the final member of the group, is a short-lived, radioactive element, formerly known as radium-emanation or niton or, depending on which radioactive series it originates in (i.e. which isotope) as radon, thoron, or actinon. It was first isolated and studied in 1902 by E. Rutherford and F. Soddy and is now universally known as radon (from radium and the termination-on adopted for the noble gases Latin radius, ray). 

F. Soddy (Oxford) contributions to knowledge of the chemistry of radioactive substances and investigations into the origin and nature of isotopes. 

Soddy, F. (1912). Matter and Energy. London Oxford University Press. 

Soddy, F. (1926). Wealth, Virtual Wealth, and Debt The Solution of the Economic Paradox. New York E. P. Dutton. 

However, an important development within atomic physics, namely the discovery of isotopy in the 1910s, led some philosophically minded chemists to reexamine Mendeleev s distinction and to rehabilitate it in a modified form. With the rapid discovery of isotopes it began to seem as though there were far more "elements" than the 90 or so which were displayed on periodic tables at the time. The work of Soddy [14], in particular, served to clarify the situation, and one that had been anticipated by Crookes,... 

Soddy, F. The Chemistry of the Radio-Elements, part 1 Longmans, Green Co. London, 1914. 

This kinetic explanation of osmotic pressure has recently received experimental support in the beautiful researches of Perrin on the Brownian movement (Urcwnian Movement and Molecular lteality, J. Perrin, trails. F. Soddy, 1910). 

As early as 1902, Rutherford and his colleague, the chemist Frederick Soddy, realized that emissions of alpha and beta rays changed the nature of the emitting substance. One example of such a change is the spontaneous radioactive decay of the uranium-238 isotope, which emits an alpha particle and produces thorium ... 

Figure 1. The three decay series from uranium, thorium, and actinium as published by Soddy in 1913 (Soddy 1913b).

Fajans K, Gohring O (1913) Uber die komplexe Natur des UrX. Naturwissenschaften 1 339 Ramsay W, Soddy F (1903) Experiments in radioactivity and the production of helium from radium. Proc R Soc London 72 204-207... 

Rutherford E (1904) The succession of changes in radioactive bodies. Philos Trans R Soc 204 169-219 Rutherford E, Soddy F (1902) The cause and nature of radioactivity Part 1. Philos Mag 4 370-396 Soddy F (1910) Radioactivity. In Annual Reports on the Progress of Chemistry, Vol. 7. The Chemical Society, London, p 257-286... 

Decay of the nuclide itself. The conceptually simplest approach is to take a known quantity of the nuclide of interest, P, and repeatedly measure it over a sufficiently long period. The observed decrease in activity with time provides the half-life to an acceptable precision and it was this technique that was originally used to establish the concept of half-lives (Rutherford 1900). Most early attempts to assess half lives, such as that for " Th depicted on the front cover of this volume, followed this method (Rutherford and Soddy 1903). This approach may use measurement of either the activity of P, or the number of atoms of P, although the former is more commonly used. Care must be taken that the nuclide is sufficiently pure so that, for instance, no parent of P is admixed allowing continued production of P during the experiment. The technique is obviously limited to those nuclides with sufficiently short half-lives that decay can readily be measured in a realistic timeframe. In practice, the longest-lived isotopes which can be assessed in this way have half-lives of a few decades (e.g., °Pb Merritt et al. 1957). 

Rutherford E (1900) A radioactive substance emitted from thorinm componnds. Philosoph Mag 49 1-14 Rutherford E, Soddy F (1903) The radioactivity of uranium. Philosoph Mag 5 441-445... 

Russell AD, Emerson S, Mix AC, Peterson LC (1996) The use of foraminiferal U/Ca as an indicator of changes in seawater uranium content. Paleoceanography 11 649-663 Rutherford E, Soddy F (1902) The cause and nature of radioactivity Part 11. Phil Mag Ser 6 4 569-585 Sacked WM (1960) Protactnium-231 content of ocean water and sediments. Science 132 1761-1762 Sacked WM (1958) Ionium-uranium ratios in marine deposited calcium carbonates and related materials. 

The normal or constant radioactivity possessed by thorium is an equilibrium value, where the rate of increase of radioactivity due to the production offresh active material is balanced by the rate of decay of radioactivity of that already formed (Rutherford and Soddy 1902). 

In the same paper, Rutherford and Soddy also suggested that elements were undergoing spontaneous transformation. The use of the word transformation smacked of alchemy and Rutherford was loath to use it, but by then it seemed clear that elements were really changing and that radioactivity may therefore be considered as a manifestation of subatomic change (Rutherford and Soddy 1902). 

Were all of these newly discovered substances also new elements This question would not be answered for some years but there was a flurry of other major discoveries to keep the protagonists occupied. Pierre Curie discovered that radioactivity released large quantities of heat (Curie and Laborde 1903) which appeared mysterious—as if the heat was coming from nowhere. This discovery provided an extra heat source for the Earth and reconciled the estimates of a very old Earth, based on geological estimates, with the young age calculated by Lord Kelvin from cooling rates. The year 1903 also witnessed the first demonstration that a-decay released He (Ramsay and Soddy 1903). The build up of He was soon put to use to date geological materials, initially by Rutherford in 1905 who calculated the first ever radiometric age of 500 Myr for a pitchblende sample, and then by Strutt who examined a wide variety of minerals (Strutt... 

Increasingly, new attempts to use basic chemistry to separate substances from radioactive material were meeting with failure. In many cases, two substances which were known to have different radioactive properties and molecular masses simply could not be separated from one another and appeared chemically identical. By 1910, this problem led Soddy to speculate that there were different forms of the same element (Soddy 1910). By 1913 he was confident of this interpretation and coined the term isotope to describe the various types of each element, recognizing that each isotope had a distinct mass and half-life (Soddy 1913b). In the same year he wrote that radiothorium, ionium, thorium, U-X, and radioactinium are a group of isotopic elements, the calculated atomic masses of which vary from 228-234 (a completely accurate statement- we now call these isotopes Th, °Th, Th, Th respectively). Soddy received the... 

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