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‎Sur la radio-activité des sels de radium. (+) Sur la radio-activité provoquée par des sels de radium. (These 2 with Debierne). (+) Sur la constante de temps caractéristique de la disparition de la radioactivité induite par leradium dansune enceinte fe...‎

‎(Paris, Gauthier-Villars), 1901. 4to. No wrappers. In: ""Comptes Rendus Hebdomadaires des Séances de L'Academie des Sciences"", Tome 133, No 5 and No 23. Pp. (969-) 1044 and pp. (909-) 966. The papers: pp. 276-279 + pp. 931-934 (both from vol. 133, and entire issues offered) + Tome 135, No 20. Pp. (821-) 880. (Entire issue offered). The paper: pp. 857-59. + Tome 136, No 4. Pp. (181-) 262. (Entire issue offered). The paper: pp. 223-226.‎

‎First printing of these four papers, constituting a revolution in time measuring, as Pierre Curie here defined a STANDARD FOR THE ABSOLUTE MEASURING OF TIME ON THE BASIS OF RADIOACTIVITY, and hereby departing from the relative measurements in geology and archaeology.After the discovery of Polonium and Actinium (1898 a. 1899 ) further discoveries followed. ""First came the announcement in 1899 by Marie Curie of induced radioactivity, brought about by the action of polonium or radium on inactive substances. The induced radioactivity persisted over a considerable period of time, a phenomenon of great concern to Pierre Curie. He took up the question with Debierne, with whom he published two papers in 1901(the first two papers offered)"" their experiments could be explained by Rutherford’s theory of emanation (radon), a radioactive gas emitted by radium. With J. Danne, Curie measured the diffusion coefficient of radium emanation in the air and proved, as Rutherford had done, that it liquefies at - 150°C. In order to clarify the nature of the emanation he studied the law of diminution of the activity of a solid after having removed it from a chamber in which a radium salt was present. In two notes presented to the Academy on 17 November 1902 and 26 January 1903 (the third and fourth papers offered), Curie showed that this activity diminishes according to an exponential law characterized by a time constant that, for the emanation, is equal to 5,752 days, regardless of the conditions of the experiment. The importance of this discovery, which marks the point of departure for all modern measurements of archaeological and geological dating, did not escape his, for at a meeting of the Société Française de Physidque in 1902 he defined a standard for the absolute measurement of time on the basis of radioactivity. Almost immediately Rutherford and Soddy showed that the exponential diminution was caused by the transmutation of radioactive elements."" (DSB. Pierre Curie).‎