In 1815, the British physician William Prout had advanced the theory that the molecular masses of elements were multiples of the mass of hydrogen. This "whole number rule" (and especially deviations from it) played an important role in the discussion whether elements could be mixtures of isotopes. F. Soddy's discovery (1910) that lead obtained by decay of uranium and of thorium differed in mass was considered a peculiarity of radioactive materials. The question of the existence of isotopes came up when the instruments developed by J.J. Thomson and by W. Wien to study cathode and canal rays by deflection in electric and magnetic fields were steadily improved. In 1913, Thomson mentioned a weak line at mass 22 accompanying the expected one at mass 20 when he analyzed the mass spectrum of neon. Subsequently Aston obtained the mass spectrum of chlorine with masses at 35 and 37. Still in 1921, Thomson objected heavily to the idea of isotopes. The isotope problem was finally settled, but more accurate mass measurements showed that even isotopic weights differed to some extent from the whole numbers. Based on earlier ideas of P. Langevin and J.-L. Costa, F.W. Aston and A.J. Dempster developed the idea of packing fractions and mass defects due to the transformation of a portion of the matter comprising the atomic nucleus into energy. While the determination of the exact isotopic masses had improved over the years, the accurate determination of isotopic abundances remained a problem as long as photographic recording was used. Here especially A.O. Nier pioneered using dual collectors and compensation measurements. This was the prerequisite for the discovery that isotopic ratios varied somewhat in nature. M. Dole discovered the fractionation of oxygen isotopes by photosynthesis and respiration. Today 13C/12C-ratios are employed to detect adulterations of food and in doping analysis, and 14C/13C-ratios obtained by accelerator mass spectrometry are used for dating historical objects, just to give some examples.

Mass spectrometry and isotopes: A century of research and discussion

The determination of isotope ratios of lead finds many important applications in earth and planetary sciences. In this study, we report the first independent and fully calibrated absolute isotope r...

High-Precision Measurements of the Isotopic Composition of Common Lead Using MC-ICPMS: Comparison of Calibration Strategies Based on Full Gravimetric Isotope Mixture and Regression Models.

Over the last thirty years, new scientific techniques have revolutionised our understanding of prehistoric economies. They enable a sound comprehension of human diet and subsistence in different environments, which is an essential framework for appreciating the rich tapestry of past human cultural variation. This volume first considers the origins of economic approaches in archaeology and the theoretical debates surrounding issues such as 'environmental determinism'. Using globally diverse examples, Alan K. Outram and Amy Bogaard critically investigate the best way to integrate newer lines of evidence such as ancient genetics, stable isotope analysis, organic residue chemistry and starch and phytolith studies with long-established forms of archaeobotanical and zooarchaeological data. Two case study chapters, on early Neolithic farming in Europe, and the origins of domestic horses and pastoralism in Central Asia, illustrate the benefit of a multi-proxy approach and how economic considerations feed into broader social and cultural questions.

/pdf/subsistence-and-society-in-prehistory-new-directions-in-1vak02f1ql.pdf

Subsistence and Society in Prehistory: New Directions in Economic Archaeology

The development of the concept of isotopy from the discovery of radio-thorium by Otto Hahn in 1905 to Soddy’s proposal of the term ‘isotope’ in 1913 is presented along with a brief review of the Fajans-Soddy group displacement laws. This is followed by a discussion of the work of Kasimir Fajans, Frederick Soddy, and others in verifying two major predictions of these laws, viz., the origin of actinium and the atomic weight of lead of radioactive origin. Within about a single month in 1914 the existence of isotopes by determination of the atomic weight of lead of radioactive origin was confirmed experimentally in four independent laboratories in four different countries — Soddy and Hyman (England, May 7), Richards and Lembert (USA, May 21), Curie (France, June 8), and Honigschmid and Horovitz (Austria, June 15) — a tribute to the international character of science. Richards and Lembert’s work has been called ‘the final act of the dramatic events surrounding the clarification of the place of the radioelements in the periodic table’.

The atomic weight of lead of radioactive origin: A confirmation of the concept of isotopy and the group displacement laws Part I

During the few years prior to World War I the science of radiochemistry saw such notable advances that, in effect, it had no more questions to ask, and it was abandoned (except for applications). The group displacement laws offered a traffic pattern for the periodic table, indicating where the daughter products of alpha- and beta-decay should be placed. The concept of isotopy permitted more than one radioelement to exist in a given box of the periodic table. The paths to these great accomplishments were numerous and intertwined. Confirmation by atomic weight measurements was more direct, and equally stirring. Human interest is added to this story of outstanding theoretical and experimental achievement by charges of plagiarism of scientific ideas.

The Suicidal Success of Radiochemistry

The atomic weight of lead of radioactive origin.

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The atomic weight of lead of radioactive origin.